C508

U s e r ’ s M a n u a l , M ay 2 00 1 C508 8-Bit CMOS Microcontroller Microcontrollers Never stop thinking. Edition 2001-05 Published by Infineon Technologies AG, St.-Martin-Strasse 53, D-81541 München, Germany © Infineon Technologies AG 2001. All Rights Reserved. Attention please! The information herein is given to describe certain components and shall not be considered as warranted characteristics. Terms of delivery and rights to technical change reserved. We hereby disclaim any and all warranties, including but not limited to warranties of non-infringement, regarding circuits, descriptions and charts stated herein. Infineon Technologies is an approved CECC manufacturer. Information For further information on technology, delivery terms and conditions and prices please contact your nearest Infineon Technologies Office in Germany or our Infineon Technologies Representatives worldwide. Warnings Due to technical requirements components may contain dangerous substances. For information on the types in question please contact your nearest Infineon Technologies Office. Infineon Technologies Components may only be used in life-support devices or systems with the express written approval of Infineon Technologies, if a failure of such components can reasonably be expected to cause the failure of that life-support device or system, or to affect the safety or effectiveness of that device or system. Life support devices or systems are intended to be implanted in the human body, or to support and/or maintain and sustain and/or protect human life. If they fail, it is reasonable to assume that the health of the user or other persons may be endangered. U s e r ’ s M a n u a l , M ay 2 00 1 C508 8-Bit CMOS Microcontroller Microcontrollers Never stop thinking. C508 User’s Manual Revision History: Previous Version: Page 2001-05 1999-10 Subjects (major changes since last revision) 3-14, 3-15, Reset value of SFR WDTH is corrected. 8-2 6-84 Block diagram of the Combined Multi-Channel PWM Modes is updated. “Phase Delay Timer” - related description is removed. − Enhanced Hooks TechnologyTM is a trademark and patent of Metalink Corporation licensed to Infineon Technologies. We Listen to Your Comments Any information within this document that you feel is wrong, unclear or missing at all? Your feedback will help us to continuously improve the quality of this document. Please send your proposal (including a reference to this document) to: mcdocu.comments@infineon.com C508 Table of Contents 1 1.1 1.2 2 2.1 2.2 3 3.1 3.2 3.3 3.4 3.4.1 3.4.2 3.4.3 3.4.4 3.4.5 3.5 4 4.1 4.1.1 4.1.2 4.1.3 4.2 4.3 4.4 4.5 4.6 4.6.1 4.6.2 4.6.3 4.6.4 4.7 4.7.1 4.7.2 4.8 5 5.1 5.2 5.3 Page Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 Pin Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4 Pin Definitions and Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6 Fundamental Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 CPU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3 CPU Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5 Memory Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 Program Memory, “Code Space” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 Data Memory, “Data Space” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 General Purpose Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 XRAM Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3 XRAM Controller Access Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3 Accesses to XRAM using the DPTR (16-bit Addressing Mode) . . . . . 3-5 Accesses to XRAM using the Registers R0/R1 (8-bit Addressing Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5 Reset Operation of the XRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9 Behavior of Port 0 and Port 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9 Special Function Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11 External Bus Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1 Accessing External Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1 Role of P0 and P2 as Data/Address Bus . . . . . . . . . . . . . . . . . . . . . . . 4-1 Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3 External Program Memory Access . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3 PSEN, Program Store Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3 Overlapping External Data and Program Memory Spaces . . . . . . . . . . . 4-3 ALE, Address Latch Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4 Enhanced Hooks Emulation Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5 Eight Datapointers for Faster External Bus Access . . . . . . . . . . . . . . . . . 4-6 The Importance of Additional Datapointers . . . . . . . . . . . . . . . . . . . . . 4-6 Implementation of the Eight Datapointers . . . . . . . . . . . . . . . . . . . . . . 4-6 Advantages of Multiple Datapointers . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7 Application Example and Performance Analysis . . . . . . . . . . . . . . . . . 4-8 ROM/OTP Protection for the C508-4R / C508-4E . . . . . . . . . . . . . . . . . 4-10 Unprotected ROM Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10 Protected ROM/OTP Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11 Version Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14 Reset and System Clock Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . Hardware Reset Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fast Internal Reset after Power-On . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hardware Reset Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-1 5-1 5-1 5-3 5-6 User’s Manual 2001-05 C508 Table of Contents 5.4 5.5 5.6 6 6.1 6.1.1 6.1.2 6.1.2.1 6.1.2.2 6.1.2.3 6.1.3 6.1.3.1 6.1.3.2 6.1.4 6.1.5 6.1.6 6.2 6.2.1 6.2.1.1 6.2.1.2 6.2.1.3 6.2.1.4 6.2.1.5 6.2.2 6.2.2.1 6.2.2.2 6.2.2.3 6.2.2.4 6.2.2.5 6.3 6.3.1 6.3.2 6.3.2.1 6.3.2.2 6.3.2.3 6.3.2.4 6.3.2.5 6.3.2.6 6.3.2.7 6.3.2.8 6.3.3 6.3.3.1 Page Clock Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7 PLL Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7 Oscillator and Clock Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8 On-Chip Peripheral Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1 Parallel I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1 Port Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1 Standard I/O Port Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4 Port 0 Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6 Port 1, Port 3, and Port 5 Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7 Port 2 Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8 Detailed Output Driver Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-10 Type B Port Driver Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-10 Type D Port Driver Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-12 Port Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-13 Port Loading and Interfacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-14 Read-Modify-Write Feature of Ports 0 to 5 (Except Port 4) . . . . . . . . 6-15 Timers/Counters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16 Timer/Counter 0 and 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16 Timer/Counter 0 and 1 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . 6-17 Mode 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-20 Mode 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-21 Mode 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-22 Mode 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-23 Timer/Counter 2 with Additional Compare/Capture/Reload . . . . . . . . 6-24 Timer 2 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26 Timer 2 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-32 Compare Function of Registers CRC, T2CC1 to T2CC3 . . . . . . . 6-34 Using Interrupts in Combination with the Compare Function . . . . 6-41 Capture Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-43 Capture/Compare Unit (CCU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-45 General Capture/Compare Unit Operation . . . . . . . . . . . . . . . . . . . . 6-46 CAPCOM Unit Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-49 CAPCOM Unit Clocking Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . 6-49 CAPCOM Unit Operating Mode 0 . . . . . . . . . . . . . . . . . . . . . . . . . 6-50 CAPCOM Unit Operating Mode 1 . . . . . . . . . . . . . . . . . . . . . . . . . 6-53 CAPCOM Unit Timing Relationships . . . . . . . . . . . . . . . . . . . . . . . 6-54 Burst Mode of CAPCOM / COMP Unit . . . . . . . . . . . . . . . . . . . . . 6-57 CAPCOM Unit in Capture Mode . . . . . . . . . . . . . . . . . . . . . . . . . . 6-58 Trap Function of the CAPCOM Unit in Compare Mode . . . . . . . . . 6-59 CAPCOM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-61 Compare (COMP) Unit Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-78 COMP Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-79 I-2 2001-05 User’s Manual C508 Table of Contents 6.3.4 6.3.4.1 6.3.4.2 6.3.4.3 6.3.4.4 6.3.4.5 6.3.4.6 6.4 6.4.1 6.4.2 6.4.3 6.4.3.1 6.4.3.2 6.4.3.3 6.4.4 6.4.5 6.4.6 6.5 6.5.1 6.5.2 6.5.3 6.5.4 6.5.5 7 7.1 7.2 7.2.1 7.2.2 7.2.3 7.3 7.4 7.5 7.6 8 8.1 8.1.1 8.1.2 8.1.3 8.1.4 8.1.5 Page Combined Multi-Channel PWM Modes . . . . . . . . . . . . . . . . . . . . . . . 6-84 Control Register BCON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-86 Signal Generation in Multi-Channel PWM Modes . . . . . . . . . . . . . 6-88 Block Commutation PWM Mode . . . . . . . . . . . . . . . . . . . . . . . . . . 6-91 Compare Timer 1 Controlled Multi-Channel PWM Modes . . . . . . . 6-94 Software Controlled State Switching in Multi-Channel PWM Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-99 Trap Function in Multi-Channel Block Commutation Mode . . . . . 6-101 Serial Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-102 Multiprocessor Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-103 Serial Port Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-103 Baudrate Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-106 Baudrate in Mode 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-107 Baudrate in Mode 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-107 Baudrate in Mode 1 and 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-108 Details about Mode 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-111 Details about Mode 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-114 Details about Modes 2 and 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-118 A/D Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-122 A/D Converter Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-122 A/D Converter Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-124 A/D Converter Clock Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-128 A/D Conversion Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-129 A/D Converter Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-133 Interrupt System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1 Structure of the Interrupt System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1 Interrupt Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7 Interrupt Enable Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7 Interrupt Request Flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-12 Interrupt Priority Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-22 Interrupt Priority Level Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-23 Interrupt Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-25 External Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-27 Interrupt Response Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-28 Fail Save Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Programmable Watchdog Timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Input Clock Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Watchdog Timer Control/Status Flags . . . . . . . . . . . . . . . . . . . . . . . . . Starting the Watchdog Timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Refreshing the Watchdog Timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Watchdog Reset and Watchdog Status Flag . . . . . . . . . . . . . . . . . . . . I-3 8-1 8-1 8-3 8-4 8-5 8-5 8-6 User’s Manual 2001-05 C508 Table of Contents 8.2 8.2.1 8.2.2 9 9.1 9.2 9.3 9.4 9.4.1 9.4.2 9.5 10 10.1 10.2 10.3 10.4 10.4.1 10.4.2 10.5 10.6 10.7 11 11.1 Page Oscillator Watchdog Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7 Detailed Description of the Oscillator Watchdog Unit . . . . . . . . . . . . . 8-8 Fast Internal Reset after Power-On . . . . . . . . . . . . . . . . . . . . . . . . . . 8-10 Power Saving Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1 Power Saving Mode Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1 Idle Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3 Slow Down Mode Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-5 Software Power Down Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-6 Invoking Software Power Down Mode . . . . . . . . . . . . . . . . . . . . . . . . . 9-6 Exit from Software Power Down Mode . . . . . . . . . . . . . . . . . . . . . . . . 9-7 State of Pins in Software Initiated Power Saving Modes . . . . . . . . . . . . 9-10 OTP Memory Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1 Programming Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1 Pin Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2 Pin Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-4 Programming Mode Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-7 Basic Programming Mode Selection . . . . . . . . . . . . . . . . . . . . . . . . . 10-7 OTP Memory Access Mode Selection . . . . . . . . . . . . . . . . . . . . . . . . 10-8 Program / Read OTP Memory Bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-9 Lock Bits Programming / Read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-11 Access of Version Bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-13 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1 Keyword Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1 User’s Manual I-4 2001-05 C508 Introduction 1 Introduction The C508 is a member of the Infineon Technologies C500 family of 8-bit microcontrollers. It is fully compatible to the standard 8051 microcontroller. Its features include extended power saving provisions, 256 × 8 on-chip RAM, 32K × 8 on-chip program memory, RFI related improvements, and the Capture Compare Unit (CCU) which is useful in motor control applications. The C508 has an internal PLL and, with a maximum CPU clock rate of 20 MHz, it achieves a 300 ns instruction cycle time. The C508 operates with internal and/or external program memory. The C508-4R contains 32K × 8 on-chip program memory (ROM version) while the C508-4E has 32K × 8 One-Time Programmable program memory (OTP version). In this document, the term C508 refers to both versions unless otherwise noted. Figure 1-1 shows the various functional units of the C508 and Figure 1-2 shows the simplified logic symbol of the C508. Oscillator Watchdog XRAM 1Kx8 XRAM 256 x 8 Port 0 I/O On-Chip Emulation Support Module 10-Bit ADC T0 Timer 2 16-Bit Capture/Compare Unit 10-Bit Compare Unit ROM/OTP 32 K x 8 CPU 8 Datapointers T1 8-Bit USART Port 1 I/O Port 2 I/O Port 3 I/O Port 4 8 Digital/Analog Inputs Watchdog Timer Port 5 I/O MCB04022 Figure 1-1 C508 Functional Units User’s Manual 1-1 2001-05 C508 Introduction Listed below is a summary of the main features of the C508 microcontroller: • Fully compatible to standard 8051 microcontroller • Superset of the 8051 architecture with eight datapointers • 10 to 20 MHz internal CPU clock (using built-in PLL with a factor of 2) – external clock of 5 - 10 MHz at 50% duty cycle – 300 ns instruction cycle time at 20 MHz CPU clock • 32 Kbytes on-chip ROM/OTP (with optional ROM protection) • 256 bytes on-chip RAM • 1024 bytes on-chip XRAM • Six 8-bit ports, – Ports 1 and 2 with enhanced current sinking capabilities of 10 mA per pin (total max. of 100 mA) – Port 4 with pure analog/digital input channels • Three 16-bit timers/counters – Timer 0 /1 (C501 compatible) – Timer 2 with four channels for 16-bit capture/compare operation • Capture/Compare Unit (CCU) for PWM (Pulse Width Modulation) signal generation – 3-channel, 16-bit capture/compare unit – 1-channel, 10-bit compare unit • Full-duplex serial interface with programmable baudrate generator (USART) • 8-channel 10-bit A/D Converter • 19 interrupt vectors with four priority levels • On-chip emulation support logic (Enhanced Hooks Technology) • Programmable 15-bit Watchdog Timer • Oscillator Watchdog • Fast Power On Reset • Power Saving Modes – Slow-down mode – Idle mode (can be combined with slow-down mode) – Software power-down mode with wake up capability through P3.2/INT0 or P5.7/ INT7 • ALE switch-off capability for reduction in RFI emission • P-MQFP-64-1, P-SDIP-64-2 packages • Temperature ranges: SAB-C508 TA = 0 to 70 °C SAF-C508 TA = -40 to 85 °C User’s Manual 1-2 2001-05 C508 Introduction VDD VSS VDDA VSSA VAREF VAGND XTAL1 XTAL2 RESET EA ALE PSEN Port 0 8-Bit Digital I/O Port 1 8-Bit Digital I/O Port 2 8-Bit Digital I/O C508 Port 3 8-Bit Digital I/O Port 4 8-Bit Digital/ Analog Inputs Port 5 8-Bit Digital I/O MCL04023 Figure 1-2 Logic Symbol User’s Manual 1-3 2001-05 C508 Introduction 1.1 Pin Configuration This section shows the pin configurations of the C508 microcontroller in the P-MQFP-64-1 and the P-SDIP-64-2 packages. P2.5/A13 P2.4/A12 P2.3/A11 P2.2/A10 P2.1/A9 P2.0/A8 VSS VDD P0.0/AD0 P0.1/AD1 P0.2/AD2 P0.3/AD3 P0.4/AD4 P0.5/AD5 P0.6/AD6 P0.7/AD7 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 49 32 50 31 30 51 52 29 53 28 27 54 55 26 56 25 C508 57 24 58 23 59 22 21 60 61 20 62 19 18 63 64 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 RESET EA XTAL1 XTAL2 P3.7/RD P3.6/WR P3.5/T1 P3.4/T0 P3.3/INT1 P3.2/INT0 P3.1/TxD P3.0/RxD P2.6/A14 P2.7/A15 PSEN ALE VDD VSS P1.0/COUT3 P1.1/CTRAP P1.2/CC0 P1.3/COUT0 P1.4/CC1 P1.5/COUT1 P1.6/CC2 P1.7/COUT2 VSS VDD P5.0/T2CC0/INT3 P5.1/T2CC1/INT4 P5.2/T2CC2/INT5 P5.3/T2CC3/INT6 P5.4/INT2 P5.5/INT9 VDDA VSSA P5.7/INT7 P5.6/INT8 P4.0/AN0 P4.1/AN1 P4.2/AN2 P4.3/AN3 P4.4/AN4 P4.5/AN5 P4.6/AN6 P4.7/AN7 VAREF VAGND MCP04024 Figure 1-3 Pin Configuration for P-MQFP-64-1 Package (top view) User’s Manual 1-4 2001-05 C508 Introduction Figure 1-4 shows the pin configuration of the C508 in the P-SDIP-64-2 package. P0.0/AD0 P0.1/AD1 P0.2/AD2 P0.3/AD3 P0.4/AD4 P0.5/AD5 P0.6/AD6 P0.7/AD7 RESET EA VDDA VSSA P4.0/AN0 P4.1/AN1 P4.2/AN2 P4.3/AN3 P4.4/AN4 P4.5/AN5 P4.6/AN6 P4.7/AN7 VAREF VAGND P5.7/INT7 P5.6/INT8 P5.5/INT9 P5.4/INT2 P5.3/T2CC3/INT6 P5.2/T2CC2/INT5 P5.1/T2CC1/INT4 P5.0/T2CC0/INT3 VDD VSS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 C508 64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 VDD VSS P2.0/A8 P2.1/A9 P2.2/A10 P2.3/A11 P2.4/A12 P2.5/A13 P2.6/A14 P2.7/A15 PSEN ALE VDD VSS XTAL1 XTAL2 P3.7/RD P3.6/WR P3.5/T1 P3.4/T0 P3.3/INT1 P3.2/INT0 P3.1/TxD P3.0/RxD P1.0/COUT3 P1.1/CTRAP P1.2/CC0 P1.3/COUT0 P1.4/CC1 P1.5/COUT1 P1.6/CC2 P1.7/COUT2 MCP04025 Figure 1-4 Pin Configuration for P-SDIP-64-2 Package (top view) User’s Manual 1-5 2001-05 C508 Introduction 1.2 Table 1-1 Symbol P1.0-P1.7 Pin Definitions and Functions Pin Definitions and Functions Pin Numbers P-MQFP-64 P-SDIP-64 32 - 25 40 - 33 I/O Port 1 is an 8-bit quasi-bidirectional port with internal pullup transistors. Port 1 pins can be used for digital input/output. Port 1 pins that have 1’s written to them are pulled high by the internal pull-up transistors and in that state can be used as inputs. As inputs, Port 1 pins being externally pulled low will source current (IIL, in the DC characteristics) because of the internal pull-up transistors. The output latch corresponding secondary function must be programmed to a one (1) for that function to operate. As secondary functions, Port 1 contains the capture/compare inputs/outputs as well as the CCU trap input. Port 1 pins have LED drive capability of up to 10 mA sinking current per pin. The secondary functions from the CCU unit are assigned to the pins of Port 1 as follows: P1.0 / COUT3 10-bit compare channel output P1.1 / CTRAP CCU trap input P1.2 / CC0 Input/Output of capture/compare Channel 0 P1.3 / COUT0 Output of capture/compare Channel 0 P1.4 / CC1 Input/Output of capture/compare Channel 1 P1.5 / COUT1 Output of capture/compare Channel 1 P1.6 / CC2 Input/Output of capture/compare Channel 2 P1.7 / COUT2 Output of capture/compare Channel 2 RESET A high level on this pin for one machine cycle while the oscillator is running resets the device. An internal diffused resistor to VSS permits power-on reset using only an external capacitor to VDD. I/O1) Function This section describes all external signals of the C508 and their functions. 32 31 30 29 28 27 26 25 RESET 1 40 39 38 37 36 35 34 33 9 I User’s Manual 1-6 2001-05 C508 Introduction Table 1-1 Symbol P3.0-P3.7 Pin Definitions and Functions (cont’d) Pin Numbers P-MQFP-64 P-SDIP-64 33 - 40 41 - 48 I/O Port 3 is an 8-bit quasi-bidirectional port with internal pullup transistors. Port 3 pins that have 1’s written to them are pulled high by the internal pull-up transistors and in that state can be used as inputs. As inputs, Port 3 pins being externally pulled low will source current (IIL, in the DC characteristics) because of the internal pull-up transistors. The output latch corresponding secondary function must be programmed to a one (1) for that function to operate (except for TxD and WR). The secondary functions are assigned to the pins of Port 3 as follows: P3.0 / RxD Receiver data input (asynch.) or data input/output (synch.) of serial interface P3.1 / TxD Transmitter data output (asynch.) or clock output (synch.) of serial interface P3.2 / INT0 External Interrupt 0 Input/Timer 0 gate control input P3.3 / INT1 External Interrupt 1 Input/Timer 1 gate control input P3.4 / T0 Timer 0 counter input P3.5 / T1 Timer 1 counter input P3.6 / WR WR control output; latches the data byte from Port 0 into the external data memory P3.7 / RD RD control output; enables the external data memory I/O1) Function 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 User’s Manual 1-7 2001-05 C508 Introduction Table 1-1 Symbol P2.0-P2.7 Pin Definitions and Functions (cont’d) Pin Numbers P-MQFP-64 P-SDIP-64 54 - 47 62 - 55 I/O Port 2 is an 8-bit quasi-bidirectional I/O port with internal pull-up transistors. Port 2 pins that have 1’s written to them are pulled high by the internal pull-up resistors, and in that state can be used as inputs. As inputs, Port 2 pins being externally pulled low will source current (IIL, in the DC characteristics) because of the internal pull-up transistors. Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses (MOVX @DPTR). In this application, it uses strong internal pull-up transistors when issuing 1’s. During accesses to external data memory that use 8-bit addresses (MOVX @Ri), Port 2 issues the contents of the P2 special function register and uses only the internal pull-up transistors. As I/O functions, Port 2 pins also have LED drive capability of up to 10 mA sinking current per pin. XTAL1 Input to the inverting oscillator amplifier and input to the internal clock generator circuits. To drive the device from an external clock source, XTAL1 should be driven, while XTAL2 is left unconnected. Minimum and maximum high and low times as well as rise/fall times specified in the AC characteristics must be observed. XTAL2 Output of the inverting oscillator amplifier. Port 4 is an 8-bit uni-directional input port to the A/D converter. Port 4 pins can be used for digital input, if voltage levels simultaneously meet the specifications for high/low input voltages and for the eight multiplexed analog inputs. I/O1) Function XTAL1 42 50 I XTAL2 P4.0-P4.7 41 5 - 12 49 13 - 20 O I User’s Manual 1-8 2001-05 C508 Introduction Table 1-1 Symbol PSEN 46 Pin Definitions and Functions (cont’d) Pin Numbers P-MQFP-64 P-SDIP-64 54 O The Program Strobe Enable output is a control signal that enables the external program memory to the bus during external fetch operations. It is activated every one and a half oscillator periods except during external data memory accesses. Remains high during internal program execution. This pin should not be driven during reset operation. The Address Latch Enable output is used for latching the low-byte of the address into external memory during normal operation. It is activated every one and a half oscillator periods except during an external data memory access. When instructions are executed from internal ROM (EA = 1) the ALE generation can be disabled by bit EALE in SFR SYSCON. This pin should not be driven during reset operation. External Access Enable When held at high level, instructions are fetched from the internal ROM when the PC is less than 8000H. When held at low level, the C508 fetches all instructions from external program memory. This pin should not be driven during reset operation. Port 0 is an 8-bit open-drain bidirectional I/O port. Port 0 pins that have 1’s written to them float, and in that state can be used as high-impedance inputs. Port 0 is also the multiplexed low-order address and data bus during accesses to external program or data memory. In this application, it uses strong internal pull-up transistors when issuing 1’s. Port 0 also outputs the code bytes during program verification in the C508-4R. External pull-up resistors are required during program verification. I/O1) Function ALE 45 53 O EA 2 10 I P0.0-P0.7 57 - 64 1-8 I/O User’s Manual 1-9 2001-05 C508 Introduction Table 1-1 Symbol P5.0-P5.7 Pin Definitions and Functions (cont’d) Pin Numbers P-MQFP-64 P-SDIP-64 22 - 15 30 - 23 I/O Port 5 is a an 8-bit quasi-bidirectional I/O port with internal pull-up transistors. Port 5 pins that have 1’s written to them are pulled high by the internal pull-up resistors, and in that state can be used as inputs. As inputs, Port 5 pins being externally pulled low will source current (IIL, in the DC characteristics) because of the internal pull-up transistors. As secondary functions, Port 5 contains the interrupt and Timer 2 capture/compare pins. They are assigned to the pins as follows: P5.0/T2CC0/INT3 T2 Compare/Capture output 0/ Interrupt 3 input P5.1/T2CC1/INT4 T2 Compare/Capture output 1/ Interrupt 4 input P5.2/T2CC2/INT5 T2 Compare/Capture output 2/ Interrupt 5 input P5.3/T2CC3/INT6 T2 Compare/Capture output 3/ Interrupt 6 input Interrupt 2 input P5.4/INT2 P5.5/INT9 Interrupt 9 input P5.6/INT8 Interrupt 8 input P5.7/INT7 Interrupt 7 input – – – – – – Ground (0 V) Power Supply (+5 V) Analog Power Supply (+5 V) Analog Ground (0 V) Reference Voltage for the A/D Converter. Reference Ground for the A/D Converter. I/O1) Function 22 21 20 19 18 17 16 15 30 29 28 27 26 25 24 23 32, 51, 63 31, 52, 64 11 12 21 22 VSS VDD VDDA VSSA VAREF VAGND 1) 24, 43, 55 23, 44, 56 3 4 13 14 I = Input O = Output User’s Manual 1-10 2001-05 C508 Fundamental Structure 2 Fundamental Structure The C508 is fully compatible with the architecture of the standard 8051/C501 microcontroller family. While maintaining all architectural and operational characteristics of the C501, the C508 incorporates a CPU with eight datapointers, a 10-bit A/D Converter, a 16-bit Capture/Compare Unit, a Timer 2 with capture/compare functions, an improved interrupt structure with four priority levels, built-in PLL with a fixed factor of 2, and an XRAM data memory, as well as some enhancements in the Fail Save Mechanism Unit. Figure 2-1 shows a block diagram of the C508 microcontroller. User’s Manual 2-1 2001-05 C508 Fundamental Structure VDD VSS XTAL1 XTAL2 RESET ALE PSEN EA C508 Oscillator Watchdog XRAM 1024 x 8 OSC & Timing PLL, factor of 2 CPU 8 Datapointers Programmable Watchdog Timer Port 0 8-Bit Digital I/O Port 1 8-Bit Digital I/O Port 2 8-Bit Digital I/O Port 3 8-Bit Digital I/O Port 4 8-Bit Analog/ Digital Input Port 5 8-Bit Digital I/O RAM 256 x 8 ROM/OTP 32 K x 8 Timer 0 Port 0 Timer 1 Port 1 Timer 2 with 4 PWM Channels USART Baudrate generator Capture/Compare Unit Port 2 Port 3 Port 4 Interrupt Unit Port 5 VAREF VAGND A/D Converter 10-Bit Emulation Support Logic S&H MUX MCB04026 Figure 2-1 Block Diagram of the C508 User’s Manual 2-2 2001-05 C508 Fundamental Structure 2.1 CPU The C508 is efficient both as a controller and as an arithmetic processor. It has extensive facilities for binary and BCD arithmetic and excels in its bit-handling capabilities. Efficient use of program memory results from an instruction set consisting of 44% one-byte, 41% two-byte, and 15% three-byte instructions. With a 10 MHz external crystal (giving a 20 MHz CPU clock), 58% of the instructions execute in 300 ns. For an 8 MHz crystal, the corresponding time is 375 ns. The Central Processing Unit (CPU) of the C508 consists of the instruction decoder, the arithmetic section, and the program control section. Each program instruction is decoded by the instruction decoder. This unit generates the internal signals controlling the functions of the individual units within the CPU. These internal signals have an effect on the source and destination of data transfers and control the Arithmetic/Logic Unit (ALU) processing. The arithmetic section of the processor performs extensive data manipulation and is comprised of the ALU, an A register, a B register, and a Program Status Word (PSW) register. The ALU accepts 8-bit data words from one or two sources and generates an 8-bit result under the control of the instruction decoder. The ALU performs the arithmetic operations: add, substract, multiply, divide, increment, decrement, BDC-decimal-add-adjust and compare, and the logic operations AND, OR, Exclusive OR, complement, and rotate (right, left or swap nibble (left four)). Also included is a Boolean processor performing the bit operations such as set, clear, complement, jump-if-set, jump-if-not-set, jump-if-setand-clear, and move to/from carry. Between any addressable bit (or its complement) and the carry flag, the ALU can perform the bit operations of logical AND or logical OR with the result returned to the carry flag. The program control section controls the sequence in which the instructions stored in program memory are executed. The 16-bit program counter (PC) holds the address of the next instruction to be executed. The conditional branch logic enables internal and external events to the processor to cause a change in the program execution sequence. Beyond the CPU functionality of the C501/8051 standard microcontroller, the C508 contains eight datapointers. For complex applications with peripherals located in the external data memory space or extended data storage capacity, this proved to be a “bottle neck” for the 8051’s communication to the external world. Programming in highlevel languages (PLM51, C51, PASCAL51) especially requires extended RAM capacity as well as fast access to this additional RAM because of the reduced code efficiency of these languages. Accumulator ACC is the symbol for the Accumulator Register. The mnemonics for accumulatorspecific instructions, however, refer to the Accumulator simply as A. User’s Manual 2-3 2001-05 C508 Fundamental Structure Program Status Word The Program Status Word (PSW) contains several status bits that reflect the current state of the CPU. Special Function Register PSW (Address D0H) Bit No. MSB D7H D0H CY D6H AC D5H F0 D4H RS1 D3H RS0 D2H OV D1H F1 Reset Value: 00H LSB D0H P PSW Bit CY AC F0 RS1 RS0 Function Carry Flag Used by arithmetic instructions. Auxiliary Carry Flag Used by instructions which execute BCD operations. General Purpose Flag 0 Register Bank select control bits These bits are used to select one of the four register banks. RS1 0 0 1 1 RS0 0 1 0 1 Function Bank 0 selected, data address 00H-07H Bank 1 selected, data address 08H-0FH Bank 2 selected, data address 10H-17H Bank 3 selected, data address 18H-1FH OV F1 P Overflow Flag Used by arithmetic instructions. General Purpose Flag 1 Parity Flag Set/cleared by hardware after each instruction to indicate an odd/ even number of “one” bits in the accumulator. B Register The B Register is used during multiply and divide and serves as both source and destination. For other instructions, it can be treated as another scratch pad register. User’s Manual 2-4 2001-05 C508 Fundamental Structure Stack Pointer The Stack Pointer (SP) Register is 8 bits wide. It is incremented before data is stored during PUSH and CALL executions and decremented after data is popped during a POP and RET (RETI) execution; that is, it always points to the last valid stack byte. While the stack may reside anywhere in the on-chip RAM, the stack pointer is initialized to 07H after a reset. This causes the stack to begin at location = 08H above register bank zero. The SP can be read or written under software control. 2.2 CPU Timing The C508 has no clock prescaler. Therefore, a machine cycle of the C508 consists of six states (3 oscillator periods). Each state is divided into a Phase 1 half and a Phase 2 half. Thus, a machine cycle consists of 3 oscillator periods, numbered S1P1 (State 1, Phase 1) through S6P2 (State 6, Phase 2). Each state lasts for half an oscillator period. Typically, arithmetic and logic operations take place during Phase 1 and internal register-to-register transfers take place during Phase 2. The diagrams in Figure 2-2 show the fetch/execute timing related to the internal states and phases. Since these internal clock signals are not user-accessible, the XTAL1 oscillator signals and the Address Latch Enable (ALE) signal are shown for external reference. ALE is normally activated twice during each machine cycle: once during S1P2 and S2P1, and again during S4P2 and S5P1. Execution of a one-cycle instruction begins at S1P2, when the op-code is latched into the Instruction Register. If it is a two-byte instruction, the second reading takes place during S4 of the same machine cycle. If it is a one-byte instruction, there is still a fetch at S4, but the byte read (which would be the next op-code) is ignored (discarded fetch), and the program counter is not incremented. In any case, execution is completed at the end of S6P2. Figure 2-2 (a) and (b) show the timings for a 1-byte, 1-cycle instruction and for a 2-byte, 1-cycle instruction. Most C508 instructions are executed in one cycle. MUL (multiply) and DIV (divide) are the only instructions that take more than two cycles to complete: they take four cycles. Normally, two code bytes are fetched from the program memory during every machine cycle. The only exception to this is when a MOVX instruction is executed. MOVX is a one-byte, 2-cycle instruction that accesses external data memory. During a MOVX, the two fetches in the second cycle are skipped while the external data memory is being addressed and strobed. Figure 2-2 (c) and (d) show the timings for a normal 1-byte, 2-cycle instruction and for a MOVX instruction. User’s Manual 2-5 2001-05 C508 Fundamental Structure S1 S2 S3 S4 S5 S6 S1 S2 S3 S4 S5 S6 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 OSC (XTAL2) ALE Read Opcode S1 S2 S3 S4 Read Next Opcode (Discard) S5 S6 Read Next Opcode Again a) 1-byte, 1-Cycle Instruction, e.g. INC A Read Opcode S1 S2 S3 S4 Read 2nd byte S5 S6 Read Next Opcode b) 2-byte, 1-Cycle Instruction, e.g. ADD A #Data Read Opcode S1 S2 S3 S4 Read Next Opcode (Discard) S5 S6 S1 S2 S3 S4 Read Next Opcode Again S5 S6 c) 1-byte, 2-Cycle Instruction, e.g. INC DPTR Read Opcode (MOVX) S1 S2 S3 S4 Read Next Opcode (Discard) S5 ADDR d) MOVX (1-byte, 2-Cycle) S6 S1 No Fetch No ALE S2 DATA S3 S4 Read Next Opcode Again No Fetch S5 S6 Access of External Memory MCD04027 Figure 2-2 Fetch Execute Sequence User’s Manual 2-6 2001-05 C508 Memory Organization 3 Memory Organization – Up to 64 Kbytes of program memory: 32K ROM for the C508-4R : 32K OTP for the C508-4E – Up to 64 Kbytes of external data memory – 256 bytes of internal data memory – 1024 bytes of internal XRAM data memory – a 128-byte special function register area. The C508 CPU manipulates operands in the following five address spaces: Figure 3-1 illustrates the memory address spaces of the C508. Alternatively FFFFH Ext. Data Memory Internal FFFFH XRAM (1 Kbyte) FC00 H FBFFH 8000H 7FFFH Int. (EA = 1) Ext. (EA = 0) 0000H "Code Space" Ext. Data Memory Indirect Addr. Internal RAM Direct Addr. Special FFH Function Regs. 80 H Internal RAM 7FH 00H Ext. 0000H "Data Space" "Internal Data Space" MCS04029 Figure 3-1 C508 Memory Map User’s Manual 3-1 2001-05 C508 Memory Organization 3.1 Program Memory, “Code Space” The C508-4R has 32 Kbytes of Read-Only program Memory (ROM), while the C508-4E provides 32 Kbytes of OTP program memory. The program memory can be externally expanded up to 64 Kbytes. If the EA pin is held high, the C508-4R executes program code out of the internal ROM unless the program counter address exceeds 7FFFH. Address locations 8000H through FFFFH are then fetched from the external program memory. If the EA pin is held low, the C508 fetches all instructions from the external program memory. 3.2 Data Memory, “Data Space” The data memory address space consists of an internal and an external memory space. The internal data memory is divided into three physically separate and distinct blocks: the lower 128 bytes of RAM, the upper 128 bytes of RAM, and the 128-byte Special Function Register (SFR). While the upper 128 bytes of data memory and the SFR area share the same address locations, they are accessed through different addressing modes. The lower 128 bytes of data memory can be accessed through direct or register indirect addressing; the upper 128 bytes of RAM can be accessed through register indirect addressing; the special function registers are accessible through direct addressing. Four 8-register banks, each bank consisting of eight 8-bit general-purpose registers, occupy locations 0 through 1FH in the lower RAM area. The next 16 bytes, locations 20H through 2FH, contain 128 directly addressable bit locations. The stack can be located anywhere in the internal RAM area, and the stack depth can be expanded up to 256 bytes. The external data memory can be expanded up to 64 Kbytes and can be accessed by instructions that use a 16-bit or an 8-bit address. The internal XRAM is located in the external address memory area at addresses FC00H to FFFFH. Using MOVX instruction with addresses pointing to this address area, allows access to either internal XRAM or external data RAM. 3.3 General Purpose Registers The lower 32 locations of the internal RAM are assigned to four banks of eight General Purpose Registers (GPRs) each. Only one of these banks may be enabled at a time. Two bits in the Program Status Word, RS0 (PSW.3) and RS1 (PSW.4), select the active register bank (see description of the PSW in Chapter 2). This allows fast context switching, which is useful when entering subroutines or interrupt service routines. The eight general purpose registers of the selected register bank may be accessed by register addressing. With register addressing, the instruction op code indicates which register is to be used. For indirect addressing, R0 and R1 are used as pointers or index registers to address internal or external memory (for example: MOV @R0). User’s Manual 3-2 2001-05 C508 Memory Organization Reset initializes the stack pointer to location 07H and increments it once to start from location 08H which is also the first register (R0) of register bank 1. Thus, if more than one register bank is required, the SP should be initialized to a different location of the RAM which is not used for data storage. 3.4 XRAM Operation The XRAM in the C508 is a memory area that is logically located at the upper end of the external data memory space, but is integrated on the chip. Because the XRAM is used in the same way as external data memory, the same instruction types (MOVX) must be used for accessing the XRAM. 3.4.1 XRAM Controller Access Control Two bits in SFR SYSCON, XMAP0 and XMAP1, control the accesses to XRAM. XMAP0 is a general access enable/disable control bit and XMAP1 controls the external signal generation during XRAM accesses. Special Function Register SYSCON (Address B1H) Bit No. MSB 7 B1H – 6 – 5 4 3 – 2 – Reset Value: XX10XX01B 1 LSB 0 SYSCON EALE RMAP XMAP1 XMAP0 The functions of the shaded bits are not described here. Bit XMAP1 Function XRAM visible access control Control bit for RD/WR signals during XRAM accesses. If addresses are outside the XRAM address range or if XRAM is disabled, this bit has no effect. XMAP1 = 0: The signals RD and WR are not activated during accesses to the XRAM. XMAP1 = 1: Ports 0, 2 and the signals RD and WR are activated during accesses to XRAM. In this mode, address and data information during XRAM accesses are visible externally. Global XRAM access enable/disable control XMAP0 = 0: The access to XRAM is enabled. XMAP0 = 1: The access to XRAM is disabled (default after reset). All MOVX accesses are performed via the external bus. Further, this bit is hardware protected. Reserved bits for future use. Read by CPU returns undefined values. XMAP0 – User’s Manual 3-3 2001-05 C508 Memory Organization When bit XMAP1 in SFR SYSCON is set, during all accesses to XRAM, RD and WR become active and Port 0 and Port 2 drive the actual address/data information which is read/written from/to XRAM. This feature allows checking of the internal data transfers to XRAM. When Ports 0 and 2 are used for I/O purposes, the XMAP1 bit should not be set; otherwise, the I/O function of the Port 0 and Port 2 lines is interrupted. After a reset operation, bit XMAP0 is set. This means that the accesses to XRAM are generally disabled. In this case, all accesses using MOVX instructions within the address range of FC00H to FFFFH generate external data memory bus cycles. When XMAP0 is cleared, the access to XRAM is enabled and all accesses using MOVX instructions with an address in the range of FC00H to FFFFH will access the internal XRAM. Bit XMAP0 is hardware protected. If it is cleared once (that is, if internal XRAM access enabled), it cannot be set by software. Only a reset operation will set the XMAP0 bit again. This hardware protection mechanism is implemented by an asymmetric latch at XMAP0 bit. An unintentional disabling of XRAM could be dangerous as indeterminate values could be read from the external bus. To avoid this, the XMAP0 bit is forced to ‘1’ only by a reset operation. Additionally, during reset, an internal capacitor is charged. So the reset status is a disabled XRAM. After a ‘0’ is written to XMAP0 bit (that is, discharging the capacitor), it is not possible to set it back again to ‘1’ due to the charge time of the capacitor. On the other hand, any distortion (such as a software hang up, noise, etc.) also cannot charge this capacitor. Thus, the stable status is the enabled XRAM. The clear instruction for the XMAP0 bit should be integrated into the program initialization routine before XRAM is used. In extremely noisy systems, the user may have redundant clear instructions. User’s Manual 3-4 2001-05 C508 Memory Organization 3.4.2 Accesses to XRAM using the DPTR (16-bit Addressing Mode) The XRAM can be accessed by two read/write instructions, which use the 16-bit DPTR for indirect addressing. These instructions are: – MOVX – MOVX A, @DPTR @DPTR, A (Read) (Write) For accessing the XRAM, the effective address stored in DPTR must be in the range of FC00H to FFFFH. 3.4.3 Accesses to XRAM using the Registers R0/R1 (8-bit Addressing Mode) The 8051 architecture also provides instructions for accesses to the external data memory range which use only an 8-bit address (indirect addressing with registers R0 or R1). The instructions are: – MOVX MOVX A, @Ri @Ri, A (Read) (Write) A special page register is implemented in the C508 to enable accessing the XRAM with the MOVX @Ri instructions as well; that is, XPAGE serves the same function for the XRAM as Port 2 does for external data memory. Special Function Register XPAGE (Address 91H) Bit No. MSB 7 91H .7 Reset Value: 00H LSB 0 .0 XPAGE 6 .6 5 .5 4 .4 3 .3 2 .2 1 .1 Bit XPAGE.7-0 Function XRAM high address XPAGE.7-0 is the address part A15-A8 when 8-bit MOVX instructions are used to access internal XRAM. Figure 3-2 to Figure 3-4 show the dependencies of XPAGE and Port 2 addressing in order to illustrate the differences in accessing XRAM, external RAM, or the use of Port 2 as an I/O-port. User’s Manual 3-5 2001-05 C508 Memory Organization Port 0 Address/Data XRAM XPAGE Write to Port 2 Port 2 Page Address MCB02112 Figure 3-2 Write Page Address to Port 2 Moving the page address to Port 2 by using either the immediate addressing instruction (MOV P2, #pageaddress) or the direct addressing instruction (MOV P2, PAL; where ‘PAL’ is the internal RAM location containing the page address) will write the page address to Port 2 and also to the XPAGE-Register. When external RAM is to be accessed in the XRAM address range, the XRAM must be disabled. When the additional external RAM is to be addressed in an address range 0000H to FC00H, the XRAM may remain enabled. User’s Manual 3-6 2001-05 C508 Memory Organization Port 0 Address/Data XRAM XPAGE Write to XPAGE Port 2 Address/ I/O-Data MCB02113 Figure 3-3 Write Page Address to XPAGE “MOV XPAGE, #pageaddress” or “MOV XPAGE, PAL”, where ‘PAL’ is internal RAM location containing the page address, will write the page address only to the XPAGE register. Port 2 is thus available for addresses or for I/O data. User’s Manual 3-7 2001-05 C508 Memory Organization Port 0 Address/Data XRAM XPAGE Write I/O Data to Port 2 Port 2 I/O-Data MCB02114 Figure 3-4 Use of Port 2 as I/O Port With a write to Port 2, the XRAM address in XPAGE register will be overwritten because of the concurrent write to Port 2 and the XPAGE register. So, whenever XRAM is used and the XRAM address differs from the byte written to the Port 2 latch, it is absolutely necessary to rewrite XPAGE with the page address. Example: I/O data at Port 2 shall be AAH. A byte shall be fetched from XRAM at address FF30H. MOV MOV MOV MOVX R0, #30H P2, #0AAH XPAGE, #0FFH A, @R0 ; ; P2 shows AAH and XPAGE contains AAH ; P2 still shows AAH but XRAM is addressed ; the contents of XRAM at FF30H is moved to the accumulator User’s Manual 3-8 2001-05 C508 Memory Organization The register XPAGE provides the upper address byte for accesses to XRAM with MOVX @Ri instructions. If the address formed by XPAGE and Ri points outside the XRAM address range, an external access is performed. For the C508, the content of XPAGE must be FCH - FFH in order to use the XRAM. The software must distinguish two cases, if the MOVX @Ri instructions with paging will be used: a) Access to XRAM: The upper address byte must be written to XPAGE or P2; both writes select the XRAM address range. b) Access to external memory: The upper address byte must be written to P2; XPAGE will be automatically loaded with the same address in order to deselect the XRAM. 3.4.4 Reset Operation of the XRAM The contents of the XRAM are not affected by a reset. After power-up, the contents are undefined, while they remain unchanged during and after a reset, as long as the power supply is not turned off. If a reset occurs during a write operation to XRAM, the effect on the contents of a XRAM memory location depends on the cycle in which the active reset signal is detected (MOVX is a two-cycle instruction): Reset during 1st cycle: Reset during 2nd cycle: The new value will not be written to XRAM. The old value is not affected. The old value in XRAM is overwritten by the new value. 3.4.5 Behavior of Port 0 and Port 2 The behavior of Port 0 and Port 2 during a MOVX access depends on the control bits in the SYSCON Register and on the state of Pin EA. Table 3-1 lists the various operating conditions. It shows the following characteristics: a) Use of P0 and P2 pins during the MOVX access. Bus: The pins work as an external address/data bus. If (internal) XRAM is accessed, the data written to the XRAM can be seen on the bus in debug mode. I/O: The pins work as Input/Output lines under control of their latch. b) Activation of the RD and WR pin during the access. c) Use of internal (XRAM) or external XDATA memory. The shaded areas in Table 3-1 describe the standard operation for each C500 device without on-chip XRAM. User’s Manual 3-9 2001-05 EA = 0 XMAP1, XMAP0 10 a)P0/P2→Bus b)RD/WR active c)ext. memory is used a)P0/P2→Bus a)P0/P2→Bus a)P0/P2→I/O (RD/WR-Data) b)RD/WR active b)RD/WR active b)RD/WR inactive c)XRAM is used c) ext. memory c)XRAM is used is used a)P0→Bus P2→I/O b)RD/WR active c)ext. memory is used a)P0/P2→I/O a)P0→Bus a)P0→Bus (RD/WR-Data) P2→I/O P2→I/O b)RD/WR active b)RD/WR active b)RD/WR inactive c)XRAM is used c)ext. memory is c)XRAM is used used a)P0→Bus P2→I/O b)RD/WR active c)ext. memory is used a)P0→Bus P2→I/O b)RD/WR active c)ext. memory is used a)P0→Bus P2→I/O b)RD/WR active c)ext. memory is used a)P0/P2→Bus a)P0/P2→Bus (RD/WR-Data) b)RD/WR active b)RD/WR active c)XRAM is used c) ext. memory is used a)P0→Bus P2→I/O b)RD/WR active c)ext. memory is used a)P0→Bus a)P0→Bus (RD/WR-Data) P2→I/O P2→I/O b)RD/WR active b)RD/WR active c)XRAM is used c)ext. memory is used a)P0/P2→Bus b)RD/WR active c)ext. memory is used a)P0/P2→Bus b)RD/WR active c)ext. memory is used a)P0/P2→Bus b)RD/WR active c)ext. memory is used a)P0/P2→Bus b)RD/WR active c)ext. memory is used X1 00 10 X1 XMAP1, XMAP0 EA = 1 User’s Manual 00 MOVX @DPTR DPTR < XRAM address range a)P0/P2→Bus b)RD/WR active c)ext. memory is used DPTR ≥ XRAM address range a)P0/P2→Bus (RD/WR-Data) b)RD/WR inactive c)XRAM is used MOVX @ Ri 3-10 XPAGE < XRAM addr. page range a)P0→Bus P2→I/O b)RD/WR active c)ext. memory is used XPAGE ≥ XRAM addr. page range a)P0→Bus (RD/WR-Data) P2→I/O b)RD/WR inactive c)XRAM is used modes compatible to 8051/C501 family Memory Organization 2001-05 Table 3-1 - Behavior of P0/P2 and RD/WR During MOVX Accesses C508 C508 Memory Organization 3.5 Special Function Registers With the exception of the program counter and the four general purpose register banks, the registers reside in the special function register area. The special function register area consists of two portions: the standard special function register area and the mapped special function register area. One special function register of the C508 (PCON1) is located in the mapped special function register area. To access the mapped special function register area, bit RMAP in the special function register SYSCON must be set. All other special function registers are located in the standard special function register area which is accessed when RMAP is cleared (0). Special Function Register SYSCON (Address B1H) Bit No. MSB 7 B1H – 6 – 5 4 3 – 2 – Reset Value: XX10XX01B 1 LSB 0 SYSCON EALE RMAP XMAP1 XMAP0 The functions of the shaded bits are not described here. Bit RMAP Function Special Function Register Map bit RMAP = 0: Access to the non-mapped (standard) special function register area is enabled. RMAP = 1: Access to the mapped special function register area is enabled. Reserved bits for future use. Read by CPU returns undefined values. – As long as bit RMAP is set, the mapped special function register area can be accessed. This bit is not cleared automatically by hardware. Thus, when non-mapped/mapped registers are to be accessed, the bit RMAP must be cleared/set respectively by software. All Special Function Registers (SFRs) with addresses whose address bits 0-2 are 0 (such as: 80H, 88H, 90H, 98H, …, F0H, F8H) are bit-addressable. The 81 SFRs in the standard and mapped SFR areas include pointers and registers that provide an interface between the CPU and the other on-chip peripherals. The SFRs of the C508 are listed in Table 3-2 and Table 3-3. In Table 3-2, they are organized in groups which refer to the functional blocks of the C508. Table 3-3 illustrates the contents of the SFRs in numeric order by their addresses. User’s Manual 3-11 2001-05 C508 Memory Organization Table 3-2 Block Special Function Registers - Functional Blocks Symbol Name Address Contents after Reset E0H3) F0H3) 83H 82H 92H D0H3) 81H B1H FCH FDH FEH D8H3) DCH D9H DAH A8H3) B8H3) 9AH BEH A9H B9H 88H3) C8H3) 98H3) C0H3) FBH 91H B1H 80H3) 90H3) A0H3) B0H3) DBH F8H3) 00H 00H 00H 00H XXXXX000B4) 00H 07H XX10XX01B4) C5H 08H 5) CPU ACC B DPH DPL DPSEL PSW SP SYSCON1) VR02) VR12) VR22) Accumulator B-Register Data Pointer, High Byte Data Pointer, Low Byte Data Pointer Select Register Program Status Word Register Stack Pointer System Control Register Version Register 0 Version Register 1 Version Register 2 A/D Converter Control Register 0 A/D Converter Control Register 1 A/D Converter Data Register High Byte A/D Converter Start Register Low Byte Interrupt Enable Register 0 Interrupt Enable Register 1 Interrupt Enable Register 2 Interrupt Enable Register 3 Interrupt Priority Register 0 Interrupt Priority Register 1 Timer Control Register Timer 2 Control Register Serial Channel Control Register Interrupt Request Control Register External Interrupt Control Register Page Address Register for Extended on-chip XRAM and CAN Controller System Control Register Port 0 Port 1 Port 2 Port 3 Port 4, Analog/Digital Input Port 5 A/DADCON01) Converter ADCON1 ADDATH ADDATL Interrupt System IEN01) IEN11) IEN2 IEN3 IP01) IP1 TCON1) T2CON1) SCON1) IRCON EINT XPAGE SYSCON1) Ports P0 P1 P2 P3 P4 P5 00X00000B4) 01XXX000B4) 00H 00XXXXXXB4) 00H X0000000B XX0000XXB XXX000XXB 00H XX000000B4) 00H 00H 00H X0000000B XX000000B 00H XX10XX01B4) FFH FFH FFH FFH – FFH XRAM User’s Manual 3-12 2001-05 C508 Memory Organization Table 3-2 Block Special Function Registers - Functional Blocks (cont’d) Symbol Name Address Contents after Reset D8H3) 87H 99H 98H3) AAH BAH 88H3) 8CH 8DH 8AH 8BH 89H C1H C3H C5H C7H C2H C4H C6H CBH CAH CDH CCH C8H3) 00X00000B4) 00H XXH4) 00H D9H XXXXXX11B4) 00H 00H 00H 00H 00H 00H 00H 00H 00H 00H 00H 00H 00H 00H 00H 00H 00H 00H Serial Channel ADCON01) PCON1) SBUF SCON SRELL SRELH TCON TH0 TH1 TL0 TL1 TMOD CCEN T2CCH1 T2CCH2 T2CCH3 T2CCL1 T2CCL2 T2CCL3 CRCH CRCL TH2 TL2 T2CON A/D Converter Control Register 0 Power Control Register Serial Channel Buffer Register Serial Channel Control Register Serial Channel Reload Register, Low Byte Serial Channel Reload Register, High Byte Timer 0/1 Control Register Timer 0, High Byte Timer 1, High Byte Timer 0, Low Byte Timer 1, Low Byte Timer Mode Register Compare/Capture Enable Register Compare/Capture Register 1, High Byte Compare/Capture Register 2, High Byte Compare/Capture Register 3, High Byte Compare/Capture Register 1, Low Byte Compare/Capture Register 2, Low Byte Compare/Capture Register 3, Low Byte Comp./Rel./Capt. Register, High Byte Comp./Rel./Capt. Register, Low Byte Timer 2, High Byte Timer 2, Low Byte Timer 2 Control Register Timer 0/ Timer 1 Timer 2 User’s Manual 3-13 2001-05 C508 Memory Organization Table 3-2 Block Special Function Registers - Functional Blocks (cont’d) Symbol Name Address Contents after Reset E1H DEH DFH E6H E7H E3H E4H E2H F2H F3H F4H F5H F6H F7H FFH F9H E5H D6H F1H D2H D3H D4H D5H D7H 84H 85H 86H A8H3) B8H3) A9H 87H 88H3) 00010000B 00H 00H 00H 00H 00H 00H FFH 00H 00H 00H 00H 00H 00H 00H 00H 00H 00H 00010000B 00H XXXXXX00B4) 00H XXXXXX00B4) 00H 00H X0000000B 00H 00H 00H 00H 00H 0XX0XXXXB4) Compare/ CT1CON Capture CCPL Unit CCPH CT1OFL CT1OFH CMSEL0 CMSEL1 COINI CCL0 CCH0 CCL1 CCH1 CCL2 CCH2 TRCON COTRAP CCIR CCIE1) CT2CON CP2L CP2H CMP2L CMP2H BCON Watchdog WDTL Timer WDTH WDTREL IEN01) IEN11) IP01) Power Save Modes 1) 2) 3) 4) 5) Compare Timer 1 Control Register Compare Timer 1 Period Register, Low Byte Compare Timer 1 Period Register, High Byte Compare Timer 1 Offset Register, Low Byte Compare Timer 1 Offset Register, High Byte Capture/Compare Mode Select Register 0 Capture/Compare Mode Select Register 1 Compare Output Initialization Register Capture/Compare Register 0, Low Byte Capture/Compare Register 0, High Byte Capture/Compare Register 1, Low Byte Capture/Compare Register 1, High Byte Capture/Compare Register 2, Low Byte Capture/Compare Register 2, High Byte Trap Enable Control Register Compare Output In Trap State Register Capture/Compare Interrupt Request Flag Reg. Capture/Compare Interrupt Enable Register Compare Timer 2 Control Register Compare Timer 2 Period Register, Low Byte Compare Timer 2 Period Register, High Byte Compare Timer 2 Compare Register, Low Byte Compare Timer 2 Compare Register, High Byte Block Commutation Control Register Watchdog Timer Register, Low Byte Watchdog Timer Register, High Byte Watchdog Timer Reload Register Interrupt Enable Register 0 Interrupt Enable Register 1 Interrupt Priority Register 0 Power Control Register Power Control Register 1 PCON1) PCON12) This special function register is listed repeatedly as some bits of it also belong to other functional blocks. This SFR is a mapped SFR. To access this SFR, bit RMAP in SFR SYSCON must be set. Bit-addressable special function registers. “X” means that the value is undefined and the location is reserved. The content of this SFR varies with the actual step of the C508 (e.g. 01H for C508-4E, first step and 11H for C508-4R, first step). User’s Manual 3-14 2001-05 C508 Memory Organization Table 3-3 Addr Contents of the SFRs, SFRs in Numeric Order by Address Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Register Content Bit 7 after Reset1) P0 SP DPL DPH WDTL WDTH FFH 07H 00H 00H 00H X0000000B .7 .7 .7 .7 .7 – WDT PSEL TF1 80H2) 81H 82H 83H 84H 85H 86H 87H 88H2) 88H 89H 8AH 8BH 8CH 8DH 90H 91H 92H 98H2) 99H 9A A0H2) A8H A9H AAH 2) 2) 3) .6 .6 .6 .6 .6 .6 .6 .5 .5 .5 .5 .5 .5 .5 IDLS TF0 – M1 .5 .5 .5 .5 .5 .5 – SM2 .5 ECT1 .5 ET2 .5 .4 .4 .4 .4 .4 .4 .4 SD TR0 WS M0 .4 .4 .4 .4 .4 .4 – REN .4 .3 .3 .3 .3 .3 .3 .3 GF1 IE1 – GATE .3 .3 .3 .3 .3 .3 – TB8 .3 .2 .2 .2 .2 .2 .2 .2 GF0 IT1 – C/T .2 .2 .2 .2 .2 .2 .2 RB8 .2 ECEM .2 EX1 .2 .2 .1 .1 .1 .1 .1 .1 .1 PDE IE0 – M1 .1 .1 .1 .1 .1 .1 .1 TI .1 – .1 ET0 .1 .1 .0 .0 .0 .0 .0 .0 .0 IDLE IT0 – M0 .0 .0 .0 .0 .0 .0 .0 RI .0 – .0 EX0 .0 .0 WDTREL 00H PCON TCON PCON1 TMOD TL0 TL1 TH0 TH1 P1 XPAGE DPSEL SCON SBUF IEN2 P2 IEN0 IP0 SRELL 00H 00H 0XX0XXXXB 00H 00H 00H 00H 00H FFH 00H XXXXX000B 00H XXH XX0000XXB FFH 00H 00H D9H SMOD PDS TR1 EWPD – GATE .7 .7 .7 .7 .7 .7 – SM0 .7 – .7 EA .7 C/T .6 .6 .6 .6 .6 .6 – SM1 .6 – .6 WDT .6 ECCM ECT2 .4 ES .4 .4 .3 ET1 .3 .3 OWDS WDTS .5 User’s Manual 3-15 2001-05 C508 Memory Organization Table 3-3 Addr Contents of the SFRs, SFRs in Numeric Order by Address (cont’d) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Register Content Bit 7 after Reset1) P3 FFH RD – – – – – – COCA H3 .7 .7 .7 .7 .7 .7 T2PS .7 .7 .7 .7 CY .7 – .7 – SYSCON XX10XX01B IEN1 IP1 SRELH IEN3 IRCON CCEN T2CCL1 T2CCL2 T2CCL3 T2CON CRCL CRCH TL2 TH2 PSW CP2L CP2H CMP2L CMP2H X0000000B XX000000B XXXXXX11B XXX000XXB X0000000B 00H 00H 00H 00H 0000X0X0B 00H 00H 00H 00H 00H 00H XXXX. XX00B 00H XXXX. XX00B B0H2) B1H B8H2) B9H BAH BEH C0H2) C1H C2H C3H C4H C5H C6H C7H C8H2) CAH CBH CCH CDH D0H2) D2H D3H D4H D5H WR – T1 EALE T0 RMAP EX5 .4 – EX9 IEX5 COCA L2 .4 .4 .4 .4 .4 .4 T2R1 .4 .4 .4 .4 RS1 .4 – .4 – INT1 – EX4 .3 – EX8 IEX4 COCA H1 .3 .3 .3 .3 .3 .3 T2R0 .3 .3 .3 .3 RS0 .3 – .3 – INT0 – EX3 .2 – EX7 IEX3 COCA L1 .2 .2 .2 .2 .2 .2 T2CM .2 .2 .2 .2 OV .2 – .2 – TxD RxD XMAP1 XMAP 0 EX2 .1 .1 – IEX2 COCA H0 .1 .1 .1 .1 .1 .1 T2I1 .1 .1 .1 .1 F1 .1 .1 .1 .1 EADC .0 .0 – IADC COCA L0 .0 .0 .0 .0 .0 .0 T2I0 .0 .0 .0 .0 P .0 .0 .0 .0 SWDT EX6 – – – TF2 COCA L3 .6 .6 .6 .6 .6 .6 I3FR .6 .6 .6 .6 AC .6 – .6 – .5 – – IEX6 COCA H2 .5 .5 .5 .5 .5 .5 I2FR .5 .5 .5 .5 F0 .5 – .5 – T2CCH1 00H T2CCH2 00H T2CCH3 00H User’s Manual 3-16 2001-05 C508 Memory Organization Table 3-3 Addr Contents of the SFRs, SFRs in Numeric Order by Address (cont’d) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Register Content Bit 7 after Reset1) CCIE BCON 00H 00H ECTP BCMP BCEM BD .9 .1 .7 D6H D7H D8H2) D9H DAH DBH DCH DEH DFH E0H2) E1H E2H E3H E4H E5H E6H E7H F0H2) F1H F2H F3H F4H F5H F6H ECTC CC2 FEN CC2 REN CC1 FEN BCER R ADM .5 – .3 – .3 .3 .3 CT1R COUT 1I CMSE L03 CMSE L23 CC1F .3 .3 .3 CT2R .3 .3 .3 .3 .3 CC1 REN BCEN MX2 .4 – .2 MX2 .2 .2 .2 CLK2 CC1I CMSE L02 CMSE L22 CC1R .2 .2 .2 CLK2 .2 .2 .2 .2 .2 CC0 FEN BCM1 MX1 .3 – .1 MX1 .1 .1 .1 CLK1 COUT 0I CMSE L01 CMSE L21 CC0F .1 .1 .1 CLK1 .1 .1 .1 .1 .1 CC0 REN BCM0 MX0 .2 – .0 MX0 .0 .0 .0 CLK0 CC0I CMSE L00 CMSE L20 CC0R .0 .0 .0 CLK0 .0 .0 .0 .0 .0 2001-05 PWM1 PWM0 EBCE CLK .8 .0 .6 – .7 – .5 BSY .6 – .4 – .4 .4 .4 CT1 RES CC2I CMSE L10 0 CC2R .4 .4 .4 CT2 RES .4 .4 .4 .4 .4 ADCON0 00X00000B ADDATH 00H ADDATL 00XXXXXXB P4 – ADCON1 01XXX000B CCPL CCPH ACC 00H 00H 00H ADCL1 ADCL0 – .7 .7 .7 CTM COUT 3I CMSE L13 ESMC .6 .6 .6 ETRP COUT XI CMSE L12 .5 .5 .5 STE1 COUT 2I CMSE L11 CT1CON 00010000B COINI FFH CMSEL0 00H CMSEL1 00H CCIR 00H NMCS 0 CT1FP CT1FC CC2F .7 .7 .7 CT2P .7 .7 .7 .7 .7 .6 .6 .6 .5 .5 .5 CT1OFL 00H CT1OFH 00H B 00H CT2CON 00010000B CCL0 CCH0 CCL1 CCH1 CCL2 00H 00H 00H 00H 00H ECT2O STE2 .6 .6 .6 .6 .6 .5 .5 .5 .5 .5 3-17 User’s Manual C508 Memory Organization Table 3-3 Addr Contents of the SFRs, SFRs in Numeric Order by Address (cont’d) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Register Content Bit 7 after Reset1) CCH2 P5 00H FFH .7 .7 BCT SEL – 1 0 .7 F7H F8H2) F9H FBH FCH 3)4) .6 .6 RES – 1 0 .6 .5 .5 .4 .4 .3 .3 .2 .2 .1 .1 .0 .0 COTRAP 00H EINT VR0 VR1 VR2 TRCON XX000000B C5H 08H 5) COUT2 CC2T T IEX9 0 0 .5 I9FR 0 0 .4 COUT1 CC1T T IEX8 0 1 .3 I8FR 1 0 .2 COUT0 CC0T T IEX7 0 0 .1 I7FR 1 0 .0 FDH 3)4) FEH 3)4) FFH 1) 2) 3) 4) 5) 00H TRPEN TRF TREN5 TREN4 TREN3 TREN2 TREN1 TREN 0 X means that the value is undefined and the location is reserved. Bit-addressable special function registers. SFR is located in the mapped SFR area. To access this SFR, bit RMAP in SFR SYSCON must be set. These are read-only registers. The content of this SFR varies with the actual step of the C508 (e.g. 01H for C508-4E, first step and 11H for C508-4R, first step). User’s Manual 3-18 2001-05 C508 External Bus Interface 4 External Bus Interface The C508 allows for external memory expansion. The functionality and implementation of the external bus interface are identical to the common interface for the 8051 architecture with one exception. The exception is the suppression of the ALE signal generation when the C508 is used in systems with no external memory. Resetting the EALE bit in SFR SYSCON gates off the ALE signal. This feature reduces RFI emissions of the system. 4.1 Accessing External Memory It is possible to distinguish between accesses to external program memory and accesses to external data memory or other peripheral components. This distinction is possible because hardware accesses to external program memory use the signal PSEN (program store enable) as a read strobe. Accesses to external data memory use RD and WR to strobe the memory (alternate functions of P3.7 and P3.6). Port 0 and Port 2 (with exceptions) are used to provide data and address signals. In this section, only the Port 0 and Port 2 functions relevant to external memory accesses are described. Fetches from external program memory always use a 16-bit address. Accesses to external data memory can use either a 16-bit address (MOVX @DPTR) or an 8-bit address (MOVX @Ri). 4.1.1 Role of P0 and P2 as Data/Address Bus When used to access external memory, Port 0 provides the data byte time-multiplexed with the low byte of the address. In this state, Port 0 is disconnected from its own port latch, and the address/data signal drives both FETs in the Port 0 output buffers. Thus, in this application, the Port 0 pins are not open-drain outputs and do not require external pull-up resistors. During any access to external memory, the CPU writes FFH to the Port 0 latch (the special function register), thus obliterating whatever information the Port 0 SFR may have been holding. Whenever a 16-bit address is used, the high byte of the address comes out on Port 2, where it is held for the duration of the read or write cycle. During this time, the Port 2 lines are disconnected from the Port 2 latch (the special function register). Thus, the Port 2 latch does not need to contain ‘1’s and the contents of the Port 2 SFR are not modified. If an 8-bit address is used (MOVX @Ri), the contents of the Port 2 SFR remain at the Port 2 pins throughout the external memory cycle. This will facilitate paging. It should be noted that, if a Port 2 pin outputs an address bit that is a ‘1’, strong pull-ups will be used for the entire read/write cycle and not only for two oscillator periods. User’s Manual 4-1 2001-05 C508 External Bus Interface a) S1 ALE One Machine Cycle S2 S3 S4 S5 S6 S1 One Machine Cycle S2 S3 S4 S5 S6 PSEN RD PCH OUT INST IN PCL OUT PCL OUT valid b) S1 ALE PCH OUT INST IN PCL OUT PCL OUT valid PCH OUT INST IN PCL OUT PCL OUT valid PCH OUT INST IN PCL OUT PCL OUT valid PCH OUT INST IN (A) without MOVX P2 P0 One Machine Cycle S2 S3 S4 S5 S6 S1 One Machine Cycle S2 S3 S4 S5 S6 PSEN (B) with MOVX PCH OUT INST IN PCL OUT PCL OUT valid PCH OUT INST IN DPL or Ri valid DPH OUT OR P2 OUT DATA IN PCL OUT PCL OUT valid PCH OUT INST IN RD P2 P0 MCD02575 Figure 4-1 External Program Memory Execution User’s Manual 4-2 2001-05 C508 External Bus Interface 4.1.2 Timing The timing of the external bus interface, in particular the relationship between the control signals ALE, PSEN, RD, WR and information on Port 0 and Port 2, is illustrated in Figure 4-1 a) and b). Data memory: In a write cycle, the data byte to be written appears on Port 0 just before WR is activated and remains there until after WR is deactivated. In a read cycle, the incoming byte is accepted at Port 0 before the read strobe is deactivated. Program memory: Signal PSEN functions as a read strobe. 4.1.3 External Program Memory Access The external program memory is accessed under two conditions: – whenever signal EA is active (low) or – whenever the program counter (PC) content is greater than 7FFFH When the CPU is executing out of external program memory, all eight bits of Port 2 are dedicated to an output function and must not be used for general-purpose I/O. The contents of the Port 2 SFR, however, are not affected. During external program memory fetches, Port 2 lines output the high byte of the PC, and during accesses to external data memory, they output either DPH or the Port 2 SFR (determined by whether external data memory access is a MOVX @DPTR or a MOVX @Ri). 4.2 PSEN, Program Store Enable The read strobe for external program memory fetches is PSEN. It is not activated for internal program memory fetches. When the CPU is accessing external program memory, PSEN is activated twice every instruction cycle (except during a MOVX instruction) whether or not the byte fetched is actually needed for the current instruction. When PSEN is activated, its timing is not the same as for RD. A complete RD cycle, including activation and deactivation of ALE and RD, takes three oscillator periods. A complete PSEN cycle, including activation and deactivation of ALE and PSEN, takes 1.5 oscillator periods. (The execution sequence for these two types of read cycles is shown in Figure 4-1 a) and b). 4.3 Overlapping External Data and Program Memory Spaces In some applications, it is desirable to execute a program from the same physical memory that is used for storing data. In the C508, the external program and data memory spaces can be combined by the logical-AND of PSEN and RD. A positive result from this AND operation produces a low active read strobe that can be used for the combined physical memory. As the PSEN cycle is faster than the RD cycle, the external memory must be fast enough to adapt to the PSEN cycle. User’s Manual 4-3 2001-05 C508 External Bus Interface 4.4 ALE, Address Latch Enable The C508 allows the ALE output signal to be switched off. If the internal ROM is used (EA = 1 and PC ≤ 7FFFH) and ALE is switched off by EALE = 0, then, ALE will go active only during external data memory accesses (MOVX instructions). If EA = 0, the ALE generation is always enabled and the bit EALE has no effect. After a hardware reset, ALE generation is enabled. Special Function Register SYSCON (Address B1H) Bit No. MSB 7 B1H – 6 – 5 EALE 4 RMAP 3 – 2 – Reset Value: XX10XX01B 1 LSB 0 SYSCON XMAP1 XMAP0 The shaded bits are not described in this section. Bit EALE Function Enable ALE output EALE = 0: ALE generation is disabled; disables ALE signal generation during internal code memory accesses (EA = 1). With EA = 1, ALE is automatically generated at MOVX instructions. EALE = 1: ALE generation is enabled. If EA = 0, the ALE generation is always enabled and the bit EALE has no effect on the ALE generation. Reserved bits for future use. Read by CPU returns undefined values. – User’s Manual 4-4 2001-05 C508 External Bus Interface 4.5 Enhanced Hooks Emulation Concept The Enhanced Hooks Emulation Concept of the C500 microcontroller family is a new, innovative way to control the execution of C500 MCUs and to gain extensive information about the internal operation of the controllers. Emulation of on-chip ROM-based programs is possible, too. Each C500 production chip has built-in logic for the support of the Enhanced Hooks Emulation Concept. Therefore, no costly bond-out chips are necessary for emulation. This also ensure that emulation and production chips are identical. The Enhanced Hooks Technology requires embedded logic in the C500 and allows the C500 when used with an EH-IC, to function in a manner similar to a bond-out chip. This simplifies the design and reduces costs of an ICE-system. ICE-systems using an EH-IC and a compatible C500 are able to emulate all operating modes of the various versions of the C500 microcontrollers. This includes emulation of ROM, ROM with code rollover, and ROMless modes of operation. It is also able to operate in single step mode and to read the SFRs after a break. ICE-System Interface to Emulation Hardware SYSCON PCON TCON RESET EA ALE PSEN RSYSCON RPCON RTCON EH-IC C500 MCU Optional I/O Ports Port 0 Port 2 Enhanced Hooks Interface Circuit Port 3 Port 1 RPort 2 RPort 0 TEA TALE TPSEN Target System Interface MCS02647 Figure 4-2 Basic C500 MCU Enhanced Hooks Concept Configuration Port 0, Port 2 and some of the control lines of the C500 based MCU are used by the Enhanced Hooks Emulation Concept to control the operation of the device during emulation and to transfer information about the program execution and data transfer between the external emulation hardware (ICE-system) and the C500 MCU. User’s Manual 4-5 2001-05 C508 External Bus Interface 4.6 4.6.1 Eight Datapointers for Faster External Bus Access The Importance of Additional Datapointers The standard 8051 architecture provides only one 16-bit pointer for indirect addressing of external devices (memories, peripherals, latches, etc.). Except for a 16-bit “move immediate” to this datapointer and an increment instruction, any other pointer handling must be handled bytewise. For complex applications with peripherals located in the external data memory space or extended data storage capacity, this factor turned out to be a “bottle neck” for the 8051’s communication to the external world. In particular, programming in high-level languages (PLM51, C51, PASCAL51) requires extended RAM capacity and at the same time a fast access to this additional RAM because of the reduced code efficiency of these languages. 4.6.2 Implementation of the Eight Datapointers Simply adding more datapointers is not suitable because of the need to keep up 100% compatibility with the 8051 instruction set. This instruction set, however, allows the handling of only one single 16-bit datapointer (DPTR, consisting of the two 8-bit SFRs DPH and DPL). To meet both of the above requirements (speed up external accesses and 100% compatibility with 8051 architecture), the C508 contains a set of eight 16-bit registers from which the actual datapointer can be selected. This means that the user’s program may keep up to eight 16-bit addresses resident in these registers; but, only one register at a time is selected to be the datapointer. Thus, the datapointer in turn is accessed (or selected) via indirect addressing. This indirect addressing is done through a special function register called DPSEL (Data Pointer Select register). All instructions of the C508 which handle the datapointer, therefore, affect only one of the eight pointers which is addressed by DPSEL at that very moment. Figure 4-3 illustrates the addressing mechanism. A 3-bit field in register DPSEL points to the DPTRx currently used. Any standard 8051 instruction (such as MOVX @DPTR, A - transfer a byte from accumulator to an external location addressed by DPTR) now uses this activated DPTRx. User’s Manual 4-6 2001-05 C508 External Bus Interface Special Function Register DPSEL (Address 92H) Bit No. MSB 7 92H – Reset Value: XXXXX000B LSB 0 .0 DPSEL 6 – 5 – 4 – 3 – 2 .2 1 .1 Bit DPSEL.2-0 Function Data Pointer Select bits DPSEL.2-0 defines the number of the actual active data pointer, DPTR0-7. ----DPSEL(92 H) DPSEL .2 0 0 0 0 1 1 1 1 .1 0 0 1 1 0 0 1 1 .0 0 1 0 1 0 1 0 1 .2 .1 .0 DPTR7 Selected Datapointer DPTR 0 DPTR 1 DPTR 2 DPTR 3 DPTR 4 DPTR 5 DPTR 6 DPTR 7 External Data Memory MCD00779 DPTR0 DPH(83 H ) DPL(82 H) Figure 4-3 Accessing of External Data Memory via Multiple Datapointers 4.6.3 Advantages of Multiple Datapointers This mechanism for addressing external data memory results in less code and faster execution of external accesses. Whenever the contents of the datapointer must be altered between two or more 16-bit addresses, one single instruction to select a new datapointer is sufficient. lf the program uses only one datapointer, then it must save the old value (with two 8-bit instructions) and load the new address, byte-by-byte. This not only takes more time, it also requires additional space in the internal RAM. User’s Manual 4-7 2001-05 C508 External Bus Interface 4.6.4 Application Example and Performance Analysis The following example demonstrates the involvement of multiple data pointers in a table transfer from the code memory to external data memory. Start address of ROM source table: 1FFFH Start address of table in external RAM: 2FA0H Example 1: Using only One Datapointer (Code for a C501) Initialization Routine MOV MOV MOV MOV LOW(SRC_PTR), #0FFH HIGH(SRC_PTR), #1FH LOW(DES_PTR), #0A0H HIGH(DES_PTR), #2FH ;Initialize shadow_variables with source_pointer ;Initialize shadow_variables with destination_pointer Table Look-up Routine under Real Time Conditions PUSH PUSH MOV MOV INC CJNE MOVC MOV MOV MOV MOV INC MOVX MOV MOV POP POP DPL DPH DPL, LOW(SRC_PTR) DPH, HIGH(SRC_PTR) DPTR … A,@DPTR LOW(SRC_PTR), DPL HIGH(SRC_PTR), DPH DPL, LOW(DES_PTR) DPH, HIGH(DES_PTR) DPTR @DPTR, A LOW(DES_PTR), DPL HIGH(DES_PTR),DPH DPH DPL ; Number of cycles ;Save old datapointer 2 ; 2 ;Load Source Pointer 2 ; 2 ;Increment and check for end of table ;(execution time ;not relevant for this consideration) – ;Fetch source data byte from ROM table 2 ;Save source_pointer and 2 ;load destination_pointer 2 ; 2 ; 2 ;Increment destination_pointer ;(ex. time not relevant) – ;Transfer byte to destination address 2 ;Save destination_pointer 2 ; 2 ;Restore old datapointer 2 ; 2 ;Total execution time (machine cycles): 28 User’s Manual 4-8 2001-05 C508 External Bus Interface Example 2: Using Two Datapointers (Code for a C508) Initialization Routine MOV MOV MOV MOV DPSEL, #06H DPTR, #1FFFH DPSEL, #07H DPTR, #2FA0H ;Initialize DPTR6 with source pointer ;Initialize DPTR7 with destination pointer Table Look-up Routine under Real Time Conditions PUSH MOV INC CJNE MOVC MOV MOVX POP DPSEL DPSEL, #06H DPTR … A,@DPTR DPSEL, #07H @DPTR, A DPSEL ; Number of cycles ;Save old source pointer 2 ;Load source pointer 2 ;Increment and check for end of table ;(execution time ;not relevant for this consideration) – ;Fetch source data byte from ROM table 2 ;Save source_pointer and ;load destination_pointer 2 ;Transfer byte to destination address 2 ;Save destination pointer and ;restore old datapointer 2 ;Total execution time (machine cycles): 12 The example above shows that utilization of the C508’s multiple datapointers can make external bus accesses twice as fast as with a standard 8051 or 8051 derivative. Here, four data variables in the internal RAM and two additional stack bytes were spared, as well. For some applications in which all eight datapointers are employed, this means that a C508 program has up to 24 bytes (16 variables and 8 stack bytes) of the internal RAM available for other uses. User’s Manual 4-9 2001-05 C508 External Bus Interface 4.7 ROM/OTP Protection for the C508-4R / C508-4E The C508-4R allows protection of the contents of the internal ROM against unauthorized read out. The type of ROM protection is fixed with the ROM mask. Therefore, users of the C508-4R version must define whether ROM protection has to be selected or not. The C508-4E OTP version also allows program memory protection at several levels (see Chapter 10.6). The program memory protection for the C508-4E can be activated after programming of the device. The C508-4R devices, which operate from internal ROM, are always checked for correct ROM contents during production test. Therefore, unprotected as well as protected ROMs must provide a procedure to verify the ROM contents. In ROM verification mode 1, which is used to verify unprotected ROMs, a ROM address is applied externally to the C5084R and the ROM data byte is output at Port 0. ROM verification mode 2, which is used to verify ROM protected devices, operates differently. In this mode, ROM addresses are generated internally and the expected data bytes must be applied externally to the device (by the manufacturer or by the customer) and are compared internally with the data bytes from the ROM. After 16 byte verify operations, the state of the P3.5 pin shows whether the last 16 bytes have been verified as expected. This mechanism provides very high security for ROM protection. Only the owner of the ROM code and the manufacturer who knows the contents of the ROM can read out and verify it. The behavior of the move code instruction, when the code is executed from the external ROM, is such that accessing a code byte from a protected on-chip ROM address is not possible. In this case, the byte accessed will be invalid. 4.7.1 Unprotected ROM Mode If the ROM is unprotected, ROM verification mode 1 as shown in Figure 4-4 is used to read out the contents of the ROM. Please refer to the AC specifications in the C508 Data Sheet for the AC timing characteristics of the ROM verification modes. P1.0-P1.7 P2.0-P2.6 Address 1 Address 2 Inputs: PSEN, P2.7 = VSS ALE, EA = VIH/VIH2 RESET = VIH1 Port 0 Data 1 OUT Data 2 OUT MCS04096 Figure 4-4 ROM Verification Mode 1 User’s Manual 4-10 2001-05 C508 External Bus Interface ROM verification mode 1 is selected if the inputs PSEN, ALE, EA, and RESET are put to the specified logic level. Then, the 15-bit address of the internal ROM byte to be read is applied to the Port 1 and Port 2 lines. After a delay, Port 0 outputs the content of the addressed ROM cell. In ROM verification mode 1, the C508 must be provided with a system clock at the XTAL pins and pull-up resistors on the Port 0 lines. 4.7.2 Protected ROM/OTP Mode If the C508-4R ROM is protected by mask (or C508-4E OTP is used in protection level 1), ROM/OTP verification mode 2 is used to verify the contents of the ROM, as shown in Figure 4-5. Please refer the AC specifications in the C508 Data Sheet for detailed timing characteristics of the ROM verification modes. RESET 12TCL 6TCL ALE 1st ALE pulse after RESET Latch Port 0 Data for Addr. 0 Latch Data for Addr. 1 Latch Data for Addr. 2 Data for Ad. X *16-1 Latch Data for Addr. X *16 Latch Data for Addr. X *16+1 P3.5 Inputs: ALE = VSS PSEN, EA = VIH / VIH2 RESET = Note: Please refer to C 508 data sheet for the definition of TCL. Verify Result for previous 16 bytes of data: Low: Verify Error High: Verify OK MCS04097 Figure 4-5 ROM Verification Mode 2 ROM/OTP verification mode 2 is selected if the inputs PSEN, EA, and ALE are put to the specified logic levels. When RESET goes inactive, the ROM/OTP verification mode 2 sequence is started. The C508 outputs an ALE signal with a period of 12TCL and expects data bytes at Port 0. The data bytes at Port 0 are assigned to the ROM addresses in the following way: User’s Manual 4-11 2001-05 C508 External Bus Interface 1. Data Byte = 2. Data Byte = 3. Data Byte = : 16. Data Byte = : contents of internal ROM/OTP address 0000H contents of internal ROM/OTP address 0001H contents of internal ROM/OTP address 0002H contents of internal ROM/OTP address 000FH The C508 does not output any address information during the ROM/OTP verification mode 2. The first data byte to be verified is always the byte which is assigned to the internal ROM address 0000H and must be put onto the data bus with the falling edge of RESET. With each following ALE pulse, the ROM/OTP address pointer is internally incremented and the expected data byte for the next ROM address must be delivered externally. Between two ALE pulses, the data at Port 0 is latched (at 6TCL after ALE rising edge) and is compared internally with the ROM/OTP contents of the actual address. If a verify error is detected, the error condition is stored internally. After each 16th data byte, the cumulated verify result (pass or fail) of the last 16 verify operations is output at P3.5. This means that P3.5 stays at a static level (low for fail and high for pass) while the next 16 bytes are checked. The output of P3.5 will be updated according to the cumulated verify result of the previous 16 bytes of data. In ROM verification mode 2, the C508 must be provided with a system clock at the XTAL pins. Figure 4-6 shows an application example of external circuitry which allows verification of a protected ROM inside the C508-4R in ROM/OTP verification mode 2. When RESET goes inactive, the C508 starts the ROM/OTP verify sequence. Its ALE is clocking a 15-bit address counter. This counter generates the addresses for an external EPROM which is programmed with the contents of the internal (protected) ROM/OTP. The verify detect logic typically displays the state of the verify error output at P3.5. P3.5 can be latched with the falling edge of ALE. The CY signal of the address counter indicates to the verify detect logic the end of the internal ROM verification. User’s Manual 4-12 2001-05 C508 External Bus Interface P3.5 Verity Detect Logic CY ALE 2 kΩ CLK 15-Bit Address Counter A0-A14 S C508-4R C508-4E & Compare Code ROM VDD RESET Port 0 & D0-D7 VDD EA CS OE PSEN MCS04098 Figure 4-6 ROM/OTP Verification Mode 2 - External Circuitry Example User’s Manual 4-13 2001-05 C508 External Bus Interface 4.8 Version Registers Version Registers are typically used for adapting the programming firmware to specific device characteristics such as ROM/OTP size etc. Three Version Registers are implemented in the C508. They can be read during normal program execution mode as mapped SFRs when the bit RMAP in SFR SYSCON is set. User’s Manual 4-14 2001-05 C508 Reset and System Clock Operation 5 5.1 Reset and System Clock Operation Hardware Reset Operation The hardware reset function incorporated in the C508 allows easy automatic startup with minimal additional hardware and forces the controller into a predefined default state. The hardware reset function can also be used during normal operation to restart the device. This is particularly useful for terminating the power-down mode. The hardware reset is applied externally to the C508. Additionally, there are three internal reset sources: the Watchdog Timer, the Oscillator Watchdog, and the PLL. This section deals with the external hardware reset only. The reset input is an active high input. An internal Schmitt trigger is used at the input for noise rejection. Since the reset is synchronized internally, the RESET pin must be held high for at least two machine cycles (six oscillator periods) while the oscillator is running. The internal reset is executed during the second machine cycle while the oscillator is running and is repeated every cycle until RESET goes low again. During reset, pins ALE and PSEN are configured as inputs and should not be stimulated externally. (External stimulation of these lines during reset activates several reserved test modes. This, in turn, may cause unpredictable output operations at several port pins). At the reset pin, a pull-down resistor is connected internally to VSS to allow a power-up reset using only an external capacitor. An automatic power-up reset can be obtained, when VDD is applied, by connecting the reset pin to VDD via a capacitor. After VDD has been turned on, the capacitor must hold the voltage level at the reset pin for a specific time to effect a complete reset. The time required for a reset operation includes the oscillator startup time, the PLL lock time, and the time for two machine cycles, must be at least 10 - 20 ms, under normal conditions. This requirement is typically met using a capacitor of 4.7 to 10 µF. The same considerations apply if the reset signal is generated externally (Figure 5-1 b). In each case, it must be assured that the oscillator has started up properly and that at least two machine cycles have passed before the reset signal goes inactive. User’s Manual 5-1 2001-05 C508 Reset and System Clock Operation VDD + VDD C508 RESET & C508 RESET + C508 RESET a) b) c) MCS04030 Figure 5-1 Reset Circuitries A correctly executed reset leaves the processor in a defined state. The program execution starts at location 0000H. After reset is internally accomplished, the port latches of Ports 0, 1, 2, 3, and 5 default to FFH. This leaves Port 0 floating, since it is an open drain port when not used as data/address bus. All other I/O port lines (Ports 1, 3 and 5) output a one (1). Port 2 lines output a zero after reset, if the EA pin is held low; or one if EA is held high. Port 4 is a uni-directional input port. It has no internal latch; therefore, the contents of the Special Function Register P4 depend on the levels applied to Port 4. The internal SFRs are set to their initial states as defined in Table 3-2. The contents of the internal RAM and XRAM of the C508 are not affected by a reset. The contents are undefined after power-up; the contents remain unchanged during reset if the power supply is not turned off. User’s Manual 5-2 2001-05 C508 Reset and System Clock Operation 5.2 Fast Internal Reset after Power-On The C508 uses the Oscillator Watchdog unit for a fast internal reset procedure after power-on. The clock source is provided by the RC Oscillator during the internal reset procedure. When the on-chip oscillator is stabilized, its clock output is multiplied by a fixed factor of two by the on-chip PLL. The clock from the PLL is then provided as the system clock. Thus, the system clock frequency is twice the external oscillator frequency. Figure 5-2 shows the power-on sequence under the control of the oscillator watchdog. Normally, devices in the 8051 family do not enter their default reset states before the onchip oscillator starts. This is because the external reset signal must be internally synchronized and processed to bring the device into the correct reset state. The start up time of the oscillator can be relatively long, especially if a crystal is used (typically 10 ms). During this period, the pins have an undefined state which could have severe effects – especially to actuators connected to port pins. The Oscillator Watchdog unit in the C508 avoids this situation because its RC Oscillator starts working within a very short startup time after power-on (typically less than 2 µs). The on-chip oscillator that feeds the PLL has not started yet, and, thus, the PLL remains unlocked. As long as the PLL is not locked, the watchdog uses the RC Oscillator output as the clock source for the chip. This allows the part to be correctly reset and also brings all ports to the defined state (see Figure 5-2, II). The exception is Port 1 which is used as compare/capture outputs. These pins will be set to their default levels as soon as the external reset is active. This is illustrated in Figure 5-3. Under worst case conditions (fast VDD rise time - such as 1 µs, measured from VDD = 4.25 V up to stable port condition), the delay between power-on and the correct port reset state is: – Typ.: – Max.: 18 µs 34 µs The RC oscillator will already run at a VDD below 4.25 V (lower specification limit). Therefore, at slower VDD rise times, the delay time will be less than the two values given above. After the on-chip oscillator has started (Figure 5-2, III) and the PLL is locked, the Oscillator Watchdog detects the correct function. Then, the watchdog continues to hold the reset active for a time period of 768 cycles (maximum) of the RC oscillator clock to ensure that a stable clock is available from the PLL (Figure 5-2, IV). Subsequently, the system clock is supplied by the PLL and the oscillator watchdog’s reset is released (Figure 5-2, V). However, an externally applied reset still remains active and the device does not start program execution before the external reset is also released (Figure 5-2, VI). User’s Manual 5-3 2001-05 Figure 5-2 User’s Manual undef. RESET I Power On undef. Port typ. 18 µ s max. 34 µ s Ports (except P1) On-chip Osc. PLL Power-On Reset of the C508 RC Osc. 5-4 II Clock from RC-Oscillator, Reset at Ports, PLL starts with base frequency but still unlocked VDD RESET III OnChip Osc starts IV V VI PLL locks; Port remains Start of Final Reset in Reset program Sequence because of execution by Osc.WD; active ext. (max. 768 RC Reset Signal Clock Cycles) MCD04031 C508 Reset and System Clock Operation 2001-05 C508 Reset and System Clock Operation Although the Oscillator Watchdog provides a fast internal reset, it is also necessary to apply the external reset signal when powering up to enable the following: – Termination of Software Power-Down Mode – Reset of the status flag OWDS that is set by the oscillator watchdog during the power up sequence. Fast reset of Port 1, that is the Compare/Capture pins, during power-on. If a crystal or ceramic resonator is used for clock generation, the external reset signal must be held active at least until the on-chip oscillator has started and the internal watchdog reset phase is completed (after phase IV in Figure 5-2). When an external clock generator is used, phase II is very short. Therefore, an external reset time of 1 ms (typical) is sufficient in most applications. Generally, an external capacitor can be connected to the RESET pin for reset time generation at power-on. Figure 5-3 is a close-up view of Phase 1 shown in Figure 5-2. When RESET is high after VDD is stable, Port 1 will be defined with its default value (high). All other ports will still remain undefined for at most 34 µs. VDD RESET Port 1 Other Ports Undefined (typ. 18 µs max. 34 µs) MCD04032 Figure 5-3 Fast Reset of Port 1 Pins User’s Manual 5-5 2001-05 C508 Reset and System Clock Operation 5.3 Hardware Reset Timing This section describes the timing of the hardware reset signal. The input pin RESET is sampled once during each machine cycle. This happens in State 5 Phase 2. Thus, the external reset signal is synchronized to the internal CPU timing. When the reset is found active (high level), the internal reset procedure is started. It needs two complete machine cycles to put the complete device into its correct reset state. In that state, all special function registers contain their default values, the port latches contain ‘1’s, etc. Note that this reset procedure is also performed if there is no clock available to the device. (This is done by the Oscillator Watchdog, which provides an auxiliary clock for performing a perfect reset without clock at the XTAL1 and XTAL2 pins). The RESET signal must be active for at least two machine cycles; after this time, the C508 remains in its reset state as long as the signal is active. When the signal goes inactive, this transition is recognized in the following State 5 Phase 2 of the machine cycle. Then, the processor starts its address output (when configured for external ROM) in the following State 5 Phase 1. One phase later (State 5 Phase 2) the first falling edge at pin ALE occurs. Figure 5-4 shows this timing for a configuration with EA = 0 (external program memory). Thus, between the release of the RESET signal and the first falling edge at ALE, there is a time period of at least one machine cycle but less than two machine cycles. One Machine Cycle S4 S5 S6 S1 P1 P2 S2 S3 S4 S5 S6 S1 S2 S3 S4 S5 S6 S1 S2 RESET P0 PCL OUT PCH OUT Inst. in PCL OUT PCH OUT P2 ALE MCT02092 Figure 5-4 CPU Timing after Reset User’s Manual 5-6 2001-05 C508 Reset and System Clock Operation 5.4 Clock Generation The top-level view of the system clock generation of the C508 is shown in Figure 5-5. fRC or fOSC PLL Freq Comp. Clkin Clkout Lock XTAL1 XTAL2 On-Chip Osc RC Osc fRC fPLL Control Logic System Clock fOSC Lock MCB04033 Figure 5-5 Block Diagram of the Clock Generation The clock generation block consists of the RC oscillator, the on-chip oscillator, and the PLL. At power-on reset, the RC oscillator takes a shorter time to start in comparison to the onchip oscillator (typically 2 µs versus 10 ms). While the on-chip oscillator is still unstable, the PLL remains unlocked. Thus, the RC clock is provided as the system clock. When the on-chip oscillator has stabilized, the PLL locks within 1 ms, providing a clock frequency twice that of the on-chip oscillator’s frequency. The system clock source is now switched to the PLL clock. External reset from the pin should be released only after this stage. 5.5 PLL Operation Within 1 ms after stable oscillations of the input clock within the specified frequency range, the PLL will be synchronous with this clock at a frequency twice that of the input frequency. In other words, the PLL locks onto its input clock. Since the PLL constantly adapts to the external clock to remain locked, the CPU clock generated has a slight variation known as jitter. This jitter is irrelevant for longer time periods. For short periods (one to four CPU clock cycles), it remains below 4%. When the PLL detects a missing input clock signal, it releases the lock signal. Consequently, an internal reset will be active until the PLL is locked again. This may occur if the input clock is unstable or fails completely; for example, due to a broken crystal. In this case, an Oscillator Watchdog reset will also occur. User’s Manual 5-7 2001-05 C508 Reset and System Clock Operation When software power-down mode is entered, the PLL is powered down together with the RC oscillator and the on-chip oscillator. In this mode, the PLL is marked unlocked; however, no internal resets will be generated. 5.6 Oscillator and Clock Circuit XTAL1 and XTAL2 are the input and output of a single-stage on-chip inverter which can be configured with off-chip components such as a Pierce oscillator. The oscillator, in any case, drives the internal clock generator. The clock generator provides the internal clock signals to the chip. These signals define the internal phases, states, and machine cycles. Figure 5-6 shows the recommended oscillator circuit. Crystal Oscillator Mode Driving from External Source External Oscillator Signal C XTAL1 5-10 MHz XTAL1 C508 XTAL2 N.C. XTAL2 C C = 20 pF + 10 pF for crystal operation (incl. Stray Capacitance) MCS04034 Figure 5-6 Recommended Oscillator Circuit In this application, the on-chip oscillator is used as a crystal-controlled, positivereactance oscillator. (A more detailed schematic is given in Figure 5-7). The on-chip oscillator is operated in its fundamental response mode as an inductive reactor in parallel resonance with a capacitor external to the chip. In this circuit, 20 pF can be used as single capacitance at any frequency together with a good quality crystal. A ceramic resonator can be used in place of the crystal in cost-critical applications. If a ceramic resonator is used, the two capacitors normally have different values depending on the oscillator frequency. It is recommended that the manufacturer of the ceramic resonator be consulted for value specifications of these capacitors. User’s Manual 5-8 2001-05 C508 Reset and System Clock Operation To internal timing circuitry C508 XTAL2 *) XTAL1 C1 C2 *) Crystal or ceramic resonator MCS04035 Figure 5-7 On-Chip Oscillator Circuitry To drive the C508 with an external clock source, the external clock signal must be applied to XTAL1, as shown in Figure 5-8. XTAL2 must be left unconnected. A pull-up resistor is suggested (to increase the noise margin), but is optional if VOH of the driving gate corresponds to the VIH3 specification of XTAL1. C508 N.C. XTAL2 VDD External Clock Signal XTAL1 MCS04036 Figure 5-8 External Clock Source User’s Manual 5-9 2001-05 C508 On-Chip Peripheral Components 6 On-Chip Peripheral Components This chapter provides detailed information about all on-chip peripherals of the C508 except for the integrated interrupt controller, which is described separately in Chapter 7. 6.1 Parallel I/O The C508 has one 8-bit analog or digital input port and five 8-bit I/O ports. Port 4 is a unidirectional input port. Port 0 is an open-drain bi-directional I/O port; Ports 1, 2, 3, and 5 are quasi-bi-directional I/O ports with internal pull-up transistors. This means that when these ports are configured as inputs, they will be pulled high and will source current when externally pulled low. Port 0 will float when configured as input. The output drivers of Ports 0 and 2 and the input buffers of Port 0 are also used for accessing external memory. In this application, Port 0 outputs the low byte of the external memory address, time multiplexed with the byte being written or read. Port 2 outputs the high byte of the external memory address when the address is 16 bits wide. Otherwise, the Port 2 pins continue emitting the P2 SFR contents. In this function, Port 0 is not an open-drain port, but uses a strong internal pull-up FET. Port 4 provides the analog input channels to the A/D Converter. 6.1.1 Port Structures The C508 generally allows digital I/O on 32 lines grouped into four bi-directional 8-bit ports and analog/digital input on one unidirectional 8-bit port. Except for Port 4 which is the uni-directional input port, each port bit consists of a latch, an output driver, and an input buffer. Read and write accesses to the I/O Ports P0-P5 (except P4) are performed via their corresponding Special Function Registers. When Port 4 is used as analog input, an analog channel is switched to the A/D Converter through a 3-bit multiplexer, which is controlled by three bits in SFR ADCON (see Chapter 6.5). Port 4 lines may also be used as digital inputs. In this case, they are addressed as an input port via SFR P4. Since Port 4 has no internal latch, the contents of SFR P4 only depend on the levels applied to the input lines. It makes no sense to output a value to this input-only port by writing to the SFR P4. This will have no effect. The parallel I/O ports of the C508 can be grouped into four different types which are listed in Table 6-1. User’s Manual 6-1 2001-05 C508 On-Chip Peripheral Components Table 6-1 Type A B C D C508 Port Structure Types Description Standard digital I/O ports which can also be used for external address/data bus. Standard multifunctional digital I/O port lines. Digital/analog uni-directional input port. Standard digital I/O with push-pull drive capability. Type A and B port pins are standard C501 compatible I/O port lines which can be used for digital I/O. Type A port (Port 0) is also designed for accessing external data or program memory. Type B port lines are located at Port 2, Port 3, and Port 5 to provide alternate functions for the serial interface, LED drive interface, and PWM signals; or are used as control outputs during external data memory accesses. Type C port (Port 4) provides the analog input port. Type D port lines can be switched to push-pull drive capability when they are used as compare outputs of the CAPCOM unit. As already mentioned, Port 1, 3, and 5 are provided for multiple alternate functions. These functions are listed in Table 6-2: User’s Manual 6-2 2001-05 C508 On-Chip Peripheral Components Table 6-2 Port P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 P1.6 P1.7 P3.0 P3.1 P3.2 P3.3 P3.4 P3.5 P3.6 P3.7 P5.0 P5.1 P5.2 P5.3 P5.4 P5.5 P5.6 P5.7 Alternate Functions of Ports 1, 3 and 5 Port Type D D D D D D D D B B B B B B B B B B B B B B B B Function 10-bit compare channel output CCU trap input CAPCOM Channel 0 input/output CAPCOM Channel 0 output CAPCOM Channel 1 input/output CAPCOM Channel 1 output CAPCOM Channel 2 input/output CAPCOM Channel 2 output Serial port’s receiver data input (asynchronous) or data input/output (synchronous) Serial port’s transmitter data output (asynchronous) or data clock output (synchronous) External interrupt 0 input External interrupt 1 input Timer 0 external counter input Timer 1 external counter input External data memory write strobe External data memory read strobe T2 Compare/Capture output 0/External interrupt 3 input T2 Compare/Capture output 1/External interrupt 4 input T2 Compare/Capture output 2/External interrupt 5 input T2 Compare/Capture output 3/External interrupt 6 input External interrupt 2 input External interrupt 9 input External interrupt 8 input External interrupt 7 input Alternate Function COUT3 CTRAP CC0 COUT0 CC1 COUT1 CC2 COUT2 RxD TxD INT0 INT1 T0 T1 WR RD T2CC0 / INT3 T2CC1 / INT4 T2CC2 / INT5 T2CC3 / INT6 INT2 INT9 INT8 INT7 User’s Manual 6-3 2001-05 C508 On-Chip Peripheral Components 6.1.2 Standard I/O Port Circuitry Figure 6-1 is a functional diagram of a typical bit latch and I/O buffer which make up the core of each of the five I/O-ports. The bit latch (one bit in the port’s SFR) is represented as a type-D flip-flop which will clock in a value from the internal bus in response to a “write-to-latch” signal from the CPU. The Q output of the flip-flop is placed on the internal bus in response to a “read-latch” signal from the CPU. The level of the port pin itself is placed on the internal bus in response to a “read-pin” signal from the CPU. Some instructions that read from a port (that is, from the corresponding port SFR P0 to P4) activate the “read-latch” signal, while others activate the “read-pin” signal. Read Latch Int. Bus Write to Latch D Q Port Latch Q CLK Port Driver Circuit Port Pin Read Pin MCS04041 Figure 6-1 Basic Structure of a Port Circuitry User’s Manual 6-4 2001-05 C508 On-Chip Peripheral Components The output drivers of Port 1, 2, 3, and 5 have internal pull-up FETs (see Figure 6-2). Each I/O line can be used independently as an input or output. To be used as an input, the port bit stored in the bit latch must contain a one (1). This means for Figure 6-2, Q = 0, which turns off the output driver FET n1. Then, for Ports 1 to 5, except Port 4, the pin is pulled high by the internal pull-ups, but can be pulled low by an external source. When externally pulled low, the port pins source current (IIL or ITL). For this reason, these ports are called “quasi-bi-directional”. Read Latch VDD Internal Pull Up Arrangement Int. Bus Write to Latch D Q Bit Latch Q CLK Port Pin n1 Read Pin MCS04042 Figure 6-2 Basic Output Driver Circuit of Ports 1, 2, 3, and 5 User’s Manual 6-5 2001-05 C508 On-Chip Peripheral Components 6.1.2.1 Port 0 Circuitry Port 0, in contrast to Ports 1 to 5, is considered a “true” bidirectional port because its pins float when configured as inputs. Thus, this port differs in not having internal pull-ups. The pull-up FET in the P0 output driver (see Figure 6-3) is used only when the port is emitting ‘1’s during the external memory accesses. Otherwise, the pull-up is always off. Consequently, P0 lines that are used as output port lines are open drain lines. Writing a ‘1’ to the port latch leaves both output FETs off and the pin floats. In this condition, it can be used as high-impedance input. If Port 0 is configured as a general I/O port and must emit logic high-level (1); then, external pull-ups are required. Read Latch Addr./ Data Control & VDD Int. Bus Write to Latch D Q Bit Latch CLK Q MUX =1 Port Pin Read Pin MCS04043 Figure 6-3 Port 0 Circuitry User’s Manual 6-6 2001-05 C508 On-Chip Peripheral Components 6.1.2.2 Port 1, Port 3, and Port 5 Circuitry The pins of Ports 1, 3, and 5 are multifunctional. They are port pins and also serve to implement special features as listed in Table 6-2. Figure 6-4 is a functional diagram of a port latch with alternate function. To pass the alternate function to the output pin and vice versa, however, the gate between the latch and driver circuit must be open. Thus, to use the alternate input or output functions, the corresponding bit latch in the port SFR must contain a one (1); otherwise, the pull-down FET is on and the port pin is stuck at ‘0’. After reset, all port latches contain ones (1). VDD Read Latch Alternate Output Function Internal Pull Up Arrangement Port Pin Int. Bus Write to Latch D Q Bit Latch CLK Q & Read Pin Alternate Input Function MCS04044 Figure 6-4 Ports 1, 3, and 5 Circuitry User’s Manual 6-7 2001-05 C508 On-Chip Peripheral Components 6.1.2.3 Port 2 Circuitry As shown in Figure 6-3 and in Figure 6-5, the output drivers of Ports 0 and 2 can be switched to an internal address or address/data bus for use in external memory accesses. In this application, these two ports cannot be used as general purpose I/O, even if not all address lines are used externally. The switching is done by an internal control signal dependent on the input level at the EA pin and/or the contents of the program counter. If the ports are configured as an address/data bus, the port latches are disconnected from the driver circuit. During this time, the P0/P2 SFR remains unchanged. As an address/data bus, Port 0 uses a pull-up FET as shown in Figure 6-3. When a 16-bit address is used, Port 2 uses the additional strong pull-ups p1 (Figure 6-5a) to emit ‘1’s for the entire external memory cycle instead of the weak ones (p2 and p3) used during normal port activity. Read Latch Addr. Control VDD Int. Bus Write to Latch D Q Bit Latch CLK Q Internal Pull Up Arrangement MUX =1 Port Pin Read Pin MCS04045 Figure 6-5 Port 2 Circuitry Port 0 can be used for I/O functions if no external bus cycles are generated using data or code memory accesses. User’s Manual 6-8 2001-05 C508 On-Chip Peripheral Components Addr. Control Q MUX ≥1 ≥1 VDD Delay p1 p2 p3 Port Pin 1 State =1 n1 VSS Input Data (Read Pin) =1 =1 MCS04046 Figure 6-5a Port 2 Pull-up Arrangement Port 2 in I/O function works in a manner similar to the Type B port driver circuitry (Chapter 6.1.3.1); whereas, in address output function it works similar to Port 0 circuitry. User’s Manual 6-9 2001-05 C508 On-Chip Peripheral Components 6.1.3 Detailed Output Driver Circuitry In fact, the pull-ups mentioned before and included in Figure 6-2, Figure 6-4, and Figure 6-5 are pull-up arrangements. The differences which apply to the various port types available in the C508 are described in the following sections. 6.1.3.1 Type B Port Driver Circuitry Figure 6-6 shows the output driver circuit of the type B multifunctional digital I/O port lines. The basic circuitry of these ports is shown in Figure 6-4. The pull-up arrangement of type B port lines has one n-channel pull-down FET and three pull-up FETs: VDD =1 Delay ≥1 p1 p2 p3 Port Pin 1 State Q n1 VSS Input Data (Read Pin) =1 =1 MCS04047 Figure 6-6 Driver Circuit of Type B Port Pins – The pull-down FET n1 is an n-channel type. It is a very strong driver transistor which is capable of sinking high currents (IOL); it is only activated if a ‘0’ is programmed to the port pin. A short circuit to VDD must be avoided if the transistor is turned on, since the high current might destroy the FET. This also means that no ‘0’ must be programmed into the latch of a pin that is used as input. – The pull-up FET p1 is a p-channel type. It is activated for two oscillator periods (S1P1 and S1P2) if a 0-to-1 transition is programmed to the port pin; that is, a ‘1’ is programmed to the port latch which contained a ‘0’. The extra pull-up can drive a similar current as the pull-down FET n1. This provides a fast transition of the logic levels at the pin. – The pull-up FET p2 is a p-channel type. It is always activated when a ‘1’ is in the port latch, thus providing the logic high output level. This pull-up FET sources a User’s Manual 6-10 2001-05 C508 On-Chip Peripheral Components much lower current than p1; therefore, the pin may also be tied to ground, for example, when used as input with logic low input level. – The pull-up FET p3 is a p-channel type. It is activated only if the voltage at the port pin is higher than approximately 1.0 to 1.5 V. This provides an additional pull-up current if a logic high level shall be output at the pin (and the voltage is not forced lower than approximately 1.0 to 1.5 V). However, this transistor is turned off if the pin is driven to a logic low level; for example, when used as input. In this configuration, only the weak pull-up FET p2 is active, which sources the current IIL. If, in addition, the pull-up FET p3 is activated, a higher current can be sourced (ITL). Thus, additional power consumption can be avoided if port pins are used as inputs with a low level applied. However, the driving capability is stronger if a logic high level is output. The activating and deactivating of the four different transistors translates into four states possible for the pins: – – – – Input low state (IL), p2 active only Input high state (IH) = steady output high state (SOH) p2 and p3 active Forced output high state (FOH), p1, p2 and p3 active Output low state (OL), n1 active If a pin is used as input and a low level is applied, it will be in IL state; if a high level is applied, it will switch to IH state. If the latch is loaded with a ‘0’, the pin will be in OL state. If the latch holds a ‘0’ and is loaded with a ‘1’, the pin will enter FOH state for two cycles and then switch to SOH state. If the latch holds a ‘1’ and is reloaded with a ‘1’, no state change will occur. At the beginning of power-on reset, the pins will be in IL state (latch is set to ‘1’, voltage level on pin is below of the trip point of p3). Depending on the voltage level and load applied to the pin, it will remain in this state or will switch to IH (= SOH) state. If it is used as output, the weak pull-up p2 will pull the voltage level at the pin above p3’s trip point after some time and p3 will turn on and provide a strong ‘1’. Note, however, that if the load exceeds the drive capability of p2 (IIL), the pin might remain in the IL state and provide a week 1 until the first 0-to-1 transition occurs on the latch. Until this happens, the output level might stay below the trip point of the external circuitry. The same is true if a pin is used as a bi-directional line and the external circuitry is switched from output to input when the pin is held at ‘0’ and the load then exceeds the p2 drive capabilities. If the load exceeds IIL, the pin can be forced to ‘1’ by writing a ‘0’ followed by a ‘1’ to the port pin. User’s Manual 6-11 2001-05 C508 On-Chip Peripheral Components 6.1.3.2 Type D Port Driver Circuitry The driver and control structure of the port pins used for Compare output functions have a port structure which allows a true push-pull output driving capability (Type D). This output driver characteristic is only enabled/used when the corresponding port lines are used as Compare outputs. The push-pull port structure is illustrated in Figure 6-7. Enable Push-Pull VDD =1 & Delay 1 State ≥1 p1 p2 p3 ≥1 Port Pin Q n1 ≥1 VSS Input Data (Read Pin) =1 =1 MCS04048 Figure 6-7 Driver Circuit of Type D Port Pins User’s Manual 6-12 2001-05 C508 On-Chip Peripheral Components 6.1.4 Port Timing When executing an instruction that changes the value of a port latch, the new value arrives at the latch during S6P2 of the final cycle of the instruction. However, port latches are only sampled by their output buffers during Phase 1 of any clock period (during Phase 2 the output buffer holds the value it noticed during the previous Phase 1). Consequently, the new value in the port latch will not appear at the output pin until the next Phase 1, which will be at S1P1 of the next machine cycle. When an instruction reads a value from a port pin (that is: MOV A, P1), the port pin is actually sampled in State 5 Phase 1 or Phase 2, depending on the port and the alternative functions. Figure 6-8 illustrates this port timing. It must be noted that this mechanism of sampling once per machine cycle is also used if a port pin is to detect an “edge”. For example, when used as counter input. In this case, an “edge” is detected when the sampled value differs from the value that was sampled the cycle before. Therefore, certain requirements must be met on the pulse length of signals in order to avoid signal “edges” not being detected. The minimum time period of high and low level is one machine cycle, which guarantees that this logic level is noticed by the port at least once. S4 S5 S6 S1 S2 S3 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 XTAL2 Input sampled: e.g.: MOV A, P1 or Port Old Data P1 active (driver transistor) New Data MCT04049 Figure 6-8 Port Timing User’s Manual 6-13 2001-05 C508 On-Chip Peripheral Components 6.1.5 Port Loading and Interfacing The output buffers of Ports 1 to 5, except Port 4 can drive TTL inputs directly. The maximum port load which still guarantees correct logic output levels can be looked up in the DC characteristics in the Data Sheet of the C508. The corresponding parameters are VOL and VOH. The same applies to Port 0 output buffers. They do, however, require external pull-ups to drive floating inputs, except when being used as the address/data bus. When used as inputs, it must be noted that the Ports 1 to 5 (except Port 4) are not floating but have internal pull-up transistors. The driving devices must be capable of sinking a sufficient current if a logic low level shall be applied to the port pin (the parameters ITL and IIL in the DC characteristics specify these currents). Port 0 however, has floating inputs when used for digital input. User’s Manual 6-14 2001-05 C508 On-Chip Peripheral Components 6.1.6 Read-Modify-Write Feature of Ports 0 to 5 (Except Port 4) Some port-reading instructions read the latch and others read the pin. The instructions reading the latch read a value, possibly change it, and then rewrite it to the latch. These are called “read-modify-write” instructions. They are listed in Table 6-3. If the destination is a port or a port pin, these instructions read the latch rather than the pin. Note that all other instructions which can be used to read a port, exclusively read the port pin. In any case, reading from latch or pin, respectively, is performed by reading the SFR P0, P2 and P3; for example, “MOV A, P3” reads the value from Port 3 pins, while “ANL P3, #0AAH” reads from the latch, modifies the value, and writes it back to the latch. It may not be obvious that the last three instructions in Table 6-3 are read-modify-write instructions, but they are. This is because they read the port byte, all 8 bits, modify the addressed bit, then write the complete byte back to the latch. Table 6-3 Instruction ANL ORL XRL JBC CPL INC DEC DJNZ CLR Px.y SETB Px.y “Read-Modify-Write”-Instructions Function Logic AND; for example: ANL P1, A Logic OR; for example: ORL P2, A Logic exclusive OR; for example: XRL P3, A Jump if bit is set and clear bit; for example: JBC P1.1, LABEL Complement bit; for example: CPL P3.0 Increment byte; for example: INC P4 Decrement byte; for example: DEC P5 Decrement and jump if not zero; for example: DJNZ P3, LABEL Clear bit y of Port x Set bit y of Port x MOV Px.y, C Move carry bit to bit y of Port x Read-modify-write instructions are directed to the latch rather than the pin to avoid a possible misinterpretation of the voltage level at the pin. For example, a port bit might be used to drive the base of a transistor. When a ‘1’ is written to the bit, the transistor is turned on. If the CPU then reads the same port bit at the pin rather than the latch, it will read the base voltage of the transistor (approx. 0.7 V, that is, a logic low level!) and interpret it as ‘0’. For example, when modifying a port bit by a SETB or CLR instruction, another bit in this port with the above mentioned configuration might be changed if the value read from the pin were written back to the latch. However, reading the latch rater than the pin will return the correct value of ‘1’. User’s Manual 6-15 2001-05 C508 On-Chip Peripheral Components 6.2 Timers/Counters The C508 contains three 16-bit timers/counters, Timer 0, Timer 1 and Timer 2. They are useful in many applications for timing and counting. In its “timer” function, the timer register is incremented every machine cycle. Thus, it can be thought of as counting machine cycles. Since a machine cycle consists of three oscillator periods, the counter rate is 1/3 of the oscillator frequency. In its “counter” function, the timer register is incremented in response to a 1-to-0 transition (falling edge) at its corresponding external input pin, T0 or T1 (alternate functions of P3.4 or P3.5 respectively). In this function, the external input is sampled during S5P2 of every machine cycle. When the samples show a high in one cycle and a low in the next cycle, the count is incremented. The new count value appears in the register during S3P1 of the cycle following the one in which the transition was detected. Since it takes two machine cycles (six oscillator periods) to recognize a transition from 1-to-0, the maximum count rate is 1/6 of the oscillator frequency. There are no restrictions on the duty cycle of the external input signal, but to ensure that a given level is sampled at least once before it changes, it must be held for at least one full machine cycle. 6.2.1 Timer/Counter 0 and 1 Timer/counter 0 and 1 of the C508 are fully compatible with timer/counter 0 and 1 of the C501 and can be used in the same four operating modes: Mode 0: 8-bit timer/counter with a divide-by-32 prescaler Mode 1: 16-bit timer/counter Mode 2: 8-bit timer/counter with 8-bit auto-reload Mode 3: Timer/counter 0 is configured as one 8-bit timer/counter and one 8-bit timer. Timer/counter 1 in this mode holds its count. The effect is the same as setting TR1 = 0. External inputs INT0 and INT1 can be programmed to function as a gate for timer/ counters 0 and 1 to facilitate pulse width measurements. Each timer consists of two 8-bit registers: TH0 and TL0 for timer/counter 0, TH1 and TL1 for timer/counter 1. These may be combined into one timer configuration depending on the mode that is established. The functions of the timers are controlled by two Special Function Registers TCON and TMOD. In the following descriptions, the symbols TH0 and TL0 are used to specify the high-byte and the low-byte of Timer 0 (TH1 and TL1 for timer 1, respectively). The operating modes are described and shown for Timer 0. If not explicitly noted, this applies also to Timer 1. User’s Manual 6-16 2001-05 C508 On-Chip Peripheral Components 6.2.1.1 Timer/Counter 0 and 1 Registers Seven special function registers control the operation of timer/counter 0 and 1: – TL0/TH0 and TL1/TH1 – counter registers, low and high part – TCON and IEN0 – control and interrupt enable – TMOD – mode select Special Function Register TL0 (Address 8AH) Special Function Register TH0 (Address 8CH) Special Function Register TL1 (Address 8BH) Special Function Register TH1 (Address 8DH) Bit No. MSB 7 .7 .7 6 .6 .6 5 .5 .5 4 .4 .4 3 .3 .3 2 .2 .2 1 .1 .1 Reset Value: 00H Reset Value: 00H Reset Value: 00H Reset Value: 00H LSB 0 .0 .0 TL0 TH0 8AH 8CH 8BH 8DH .7 .6 .5 .4 .3 .2 .1 .0 TL1 .7 .6 .5 .4 .3 .2 .1 .0 TH1 Bit TLx.7-0 x = 0-1 Function Timer/counter 0/1 low register Operating Mode Description 0 1 2 3 “TLx” holds the 5-bit prescaler value. “TLx” holds the lower 8-bit part of the 16-bit timer/counter value. “TLx” holds the 8-bit timer/counter value. TL0 holds the 8-bit timer/counter value; TL1 is not used. THx.7-0 x = 0-1 Timer/counter 0/1 high register Operating Mode Description 0 1 2 3 “THx” holds the 8-bit timer/counter value. “THx” holds the higher 8-bit part of the 16-bit timer/counter value. “THx” holds the 8-bit reload value. TH0 holds the 8-bit timer value; TH1 is not used. User’s Manual 6-17 2001-05 C508 On-Chip Peripheral Components Special Function Register TCON (Address 88H) Special Function Register IEN0 (Address A8H) Bit No. MSB 7 8FH 88H TF1 6 8EH TR1 5 8DH TF0 4 8CH TR0 3 8BH IE1 2 8AH IT1 1 89H IE0 Reset Value: 00H Reset Value: 00H LSB 0 88H IT0 TCON AFH A8H EA AEH WDT ADH ET2 ACH ES0 ABH ET1 AAH EX1 A9H ET0 A8H EX0 IEN0 The shaded bits are not used for controlling timer/counter 0 and 1. Bit TF1 Function Timer 1 overflow flag Set by hardware on timer/counter overflow. Cleared by hardware when processor vectors to interrupt routine. Timer 1 run control bit Set/cleared by software to turn timer/counter 1 ON/OFF. Timer 0 overflow flag Set by hardware on timer/counter overflow. Cleared by hardware when processor vectors to interrupt routine. Timer 0 run control bit Set/cleared by software to turn timer/counter 0 ON/OFF. Timer 1 overflow interrupt enable If ET1 = 0, the timer 1 interrupt is disabled. Timer 0 overflow interrupt enable If ET0 = 0, the timer 0 interrupt is disabled. TR1 TF0 TR0 ET1 ET0 User’s Manual 6-18 2001-05 C508 On-Chip Peripheral Components Special Function Register TMOD (Address 89H) Bit No. 89H MSB 7 Gate 6 C/T 5 M1 4 M0 3 Gate 2 C/T 1 M1 Reset Value: 00H LSB 0 M0 TMOD Timer 1 Control Timer 0 Control Bit GATE Function Gating control When set, timer/counter “x” is enabled only while “INT x” pin is high and “TRx” control bit is set. When cleared timer “x” is enabled whenever “TRx” control bit is set. Counter or timer select bit Set for counter operation (input from “Tx” input pin). Cleared for timer operation (input from internal system clock). Mode select bits M1 0 M0 0 Function 8-bit timer/counter: “THx” operates as 8-bit timer/counter “TLx” serves as 5-bit prescaler 16-bit timer/counter. “THx” and “TLx” are cascaded; there is no prescaler 8-bit auto-reload timer/counter. “THx” holds a value which is to be reloaded into “TLx” each time it overflows Timer 0: TL0 is an 8-bit timer/counter controlled by the standard timer 0 control bits. TH0 is an 8-bit timer only controlled by timer 1 control bits. Timer 1: Timer/counter 1 stops C/T M1 M0 0 1 1 0 1 1 User’s Manual 6-19 2001-05 C508 On-Chip Peripheral Components 6.2.1.2 Mode 0 Putting either Timer/counter 0 or Timer/counter 1 into mode 0 configures it as an 8-bit timer/counter with a divide-by-32 prescaler. Figure 6-9 shows the mode 0 operation. In this mode, the timer register is configured as a 13-bit register. As the count rolls over from all ‘1’s to all ‘0’s, it sets the timer overflow flag TF0. The overflow flag TF0 then can be used to request an interrupt. The counted input is enabled to the timer when TR0 = 1 and either Gate = 0 or INT0 = 1 (setting Gate = 1 allows the timer to be controlled by external input INT0, to facilitate pulse width measurements). TR0 is a control bit in the special function register TCON; Gate is in TMOD. The 13-bit register consists of all eight bits of TH0 and the lower 5 bits of TL0. The upper three bits of TL0 are indeterminate and should be ignored. Setting the run flag (TR0) does not clear the registers. Mode 0 operation is the same for Timer 0 as for Timer 1. Substitute TR0, TF0, TH0, TL0 and INT0 for the corresponding Timer 1 signals in Figure 6-9. There are two different gate bits, one for Timer 1 (TMOD.7) and one for Timer 0 (TMOD.3). OSC ÷3 C/T = 0 TL0 (5 Bits) C/T = 1 P3.4/T0 Pin TH0 (8 Bits) TF0 Interrupt Control TR0 & Gate =1 ≥1 P3.2/INT0 Pin MCS04050 Figure 6-9 Timer/Counter 0, Mode 0: 13-Bit Timer/Counter User’s Manual 6-20 2001-05 C508 On-Chip Peripheral Components 6.2.1.3 Mode 1 Mode 1 is the same as mode 0, except that the timer register is running with all 16 bits. Mode 1 is shown in Figure 6-10. OSC ÷3 C/T = 0 TL0 (8 Bits) C/T = 1 P3.4/T0 Pin TH0 (8 Bits) TF0 Interrupt Control TR0 & Gate =1 ≥1 P3.2/INT0 Pin MCS04051 Figure 6-10 Timer/Counter 0, Mode 1: 16-Bit Timer/Counter User’s Manual 6-21 2001-05 C508 On-Chip Peripheral Components 6.2.1.4 Mode 2 Mode 2 configures the timer register as an 8-bit counter (TL0) with automatic reload, as shown in Figure 6-11. Overflow from TL0 not only sets TF0, but also reloads TL0 with the contents of TH0, which is preset by software. The reload leaves TH0 unchanged. OSC ÷3 C/T = 0 TL0 (8 Bits) C/T = 1 P3.4/T0 Pin TF0 Interrupt Control Reload TR0 & Gate =1 ≥1 TH0 (8 Bits) P3.2/INT0 Pin MCS04052 Figure 6-11 Timer/Counter 0, 1, Mode 2: 8-Bit Timer/Counter with Auto-Reload User’s Manual 6-22 2001-05 C508 On-Chip Peripheral Components 6.2.1.5 Mode 3 Mode 3 has different effects on Timer 0 and Timer 1. Timer 1 in mode 3 simply holds its count. The effect is the same as setting TR1 = 0. Timer 0 in mode 3 establishes TL0 and TH0 as two separate counters. The logic for mode 3 on Timer 0 is shown in Figure 6-12. TL0 uses the Timer 0 control bits: C/T, Gate, TR0, INT0 and TF0. TH0 is locked into a timer function (counting machine cycles) and takes over the use of TR1 and TF1 from Timer 1. Thus, TH0 now controls the “Timer 1” interrupt. Mode 3 is provided for applications requiring an extra 8-bit timer or counter. When Timer 0 is in mode 3 and when TR1 is set, Timer 1 can be turned on by switching it to any mode other than 3 and off by switching it into its own mode 3, or can still be used by the serial channel as a baudrate generator, or in fact, in any application not requiring an interrupt from timer 1 itself. OSC ÷3 C/T = 0 TL0 (8 Bits) C/T = 1 P3.4/T0 Pin Timer Clock TF0 Interrupt Control TR0 TR0 & Gate =1 ≥1 P3.2/INT0 Pin TH0 (8 Bits) TR1 TF1 Interrupt MCS04053 Figure 6-12 Timer/Counter 0, Mode 3: Two 8-Bit Timers/Counters User’s Manual 6-23 2001-05 C508 On-Chip Peripheral Components 6.2.2 Timer/Counter 2 with Additional Compare/Capture/Reload Timer 2 with additional Compare/Capture/reload features is one of the most powerful peripheral units of the C508. lt can be used for various digital signal generation and event capturing like pulse generation, pulse width modulation, pulse width measuring etc. Timer 2 is designed to support various automotive control applications as well as industrial applications (frequency generation, digital-to-analog conversion, process control etc.). Please note that the functionality of this timer is not equivalent to the functionality of Timer 2 of the C501. The C508 Timer 2 used in combination with the Compare/Capture/reload registers allows the following operating modes: – Compare: Up to 4 PWM output signals with 65535 steps at maximum, and 300 ns resolution – Capture: Up to 4 high speed Capture inputs with 300 ns resolution – Reload: Modulation of timer 2 cycle time The block diagram in Figure 6-13 shows the general configuration of Timer 2 with the additional Compare/Capture/reload registers. The I/O pins which can be used for Timer 2 control are located as multifunctional port functions at Port 5 (see Figure 6-4). Table 6-4 Pin Symbol P5.0 / T2CC0 / INT3 P5.1 / T2CC1 / INT4 P5.2 / T2CC2 / INT5 P5.3 / T2CC3 / INT6 Alternate Port Functions of Timer 2 Function Compare output/Capture input for CRC Register Compare output/Capture input for CC Register 1 Compare output/Capture input for CC Register 2 Compare output/Capture input for CC Register 3 User’s Manual 6-24 2001-05 C508 On-Chip Peripheral Components Reload ÷3 OSC ÷6 T2PS Reload T2I0 = '1' and T2I1 = '0' Timer 2 TL2 TH2 TF2 Interrupt Request Compare P5.0/ T2CC0/ INT3 16-Bit Comparator 16-Bit Comparator 16-Bit Comparator 16-Bit Comparator P5.1/ T2CC1/ INT4 P5.2/ T2CC2/ INT5 P5.3/ T2CC3/ INT6 T2CCL3/ T2CCH3 T2CCL2/ T2CCH2 T2CCL1/ T2CCH1 CRCL/ CRCH MCB04054 Input/ Output Control Capture Figure 6-13 Timer 2 Block Diagram User’s Manual 6-25 2001-05 C508 On-Chip Peripheral Components 6.2.2.1 Timer 2 Registers This section describes all Timer 2 related special function registers. The interrupt related SFRs are also included in this section. Table 6-5 summarizes the Timer 2 SFRs. Table 6-5 Symbol T2CON TL2 TH2 CCEN CRCL CRCH T2CCL1 T2CCH1 T2CCL2 T2CCH2 T2CCL3 T2CCH3 IEN0 IEN1 IRCON Special Function Registers of the Timer 2 Unit Description Timer 2 Control Register Timer 2, Low Byte Timer 2, High Byte Compare/Capture enable register Compare/Reload/Capture register, low byte Compare/Reload/Capture register, high byte Compare/Capture Register 1, Low Byte Compare/Capture Register 1, High Byte Compare/Capture Register 2, Low Byte Compare/Capture Register 2, High Byte Compare/Capture Register 3, Low Byte Compare/Capture Register 3, High Byte Interrupt Enable Register 0 Interrupt Enable Register 1 Interrupt Control Register Address C8H CCH CDH C1H CAH CBH C2H C3H C4H C5H C6H C7H A8H B8H C0H The T2CON Timer 2 control register is a bit-addressable register which controls the Timer 2 function and the Compare mode of registers CRC, T2CC1 to T2CC3. User’s Manual 6-26 2001-05 C508 On-Chip Peripheral Components Special Function Register T2CON (Address C8H) Bit No. MSB 7 CFH C8H T2PS 6 CEH I3FR 5 CDH I2FR 4 CCH T2R1 3 CBH T2R0 2 CAH T2CM 1 C9H T2I1 Reset Value: 00H LSB 0 C8H T2I0 T2CON The shaded bits are not used for controlling Timer/counter 2. Bit T2PS Function Prescaler select bit When set, Timer 2 is clocked with 1/6 of the oscillator frequency. When cleared, Timer 2 is clocked with 1/3 of the oscillator frequency. External interrupt 3 falling / rising edge flag Used for Capture function in combination with register CRC. If set, a Capture to register CRC (if enabled) will occur on a positive transition at pin P5.0/T2CC0/INT3. Timer 2 Reload enable T2R0 0 0 1 T2R1 0 1 X Function Reload disabled Auto-Reload upon Timer 2 overflow (TF2) Prohibited. Do not use this combination. I3FR T2R1 T2R0 T2CM Compare mode bit for registers CRC, T2CC1 through T2CC3 T2CM 0 1 Function Compare mode 0 is selected Compare mode 1 is selected T2I1 T2I0 Timer 2 input selection T2I0 0 1 T2I1 0 0 Function No input selected, Timer 2 stops Timer function: input frequency = fosc/3 (T2PS = 0) or fosc/6 (T2PS = 1) Prohibited. Do not use this combination. X 1 User’s Manual 6-27 2001-05 C508 On-Chip Peripheral Components Special Function Register TL2 (Address CCH) Special Function Register TH2 (Address CDH) Special Function Register CRCL (Address CAH) Special Function Register CRCH (Address CBH) Bit No. MSB 7 .7 6 .6 5 .5 4 .4 3 .3 2 .2 1 .1 Reset Value: 00H Reset Value: 00H Reset Value: 00H Reset Value: 00H LSB 0 LSB TL2 CCH CDH MSB .6 .5 .4 .3 .2 .1 .0 TH2 CAH .7 .6 .5 .4 .3 .2 .1 LSB CRCL CBH MSB .6 .5 .4 .3 .2 .1 .0 CRCH Bit TL2.7-0 TH2.7-0 CRCL.7-0 Function Timer 2 Value Low Byte The TL2 register holds the low byte of the 16-bit Timer 2 count value. Timer 2 Value High Byte The TH2 register holds the high byte of the 16-bit Timer 2 count value. Reload Register Low Byte CRCL is the low byte of the 16-bit reload register of Timer 2. It is also used for Compare/Capture functions. Reload Register High Byte CRCH is the high byte of the 16-bit reload register of Timer 2. It is also used for Compare/Capture functions. CRCH.7-0 User’s Manual 6-28 2001-05 C508 On-Chip Peripheral Components Special Function Register IEN0 (Address A8H) Special Function Register IRCON (Address C0H) MSB AFH EA Reset Value: 00H Reset Value: X0000000B LSB A8H EX0 IEN0 Bit No. A8H AEH WDT ADH ET2 ACH ES ABH ET1 AAH EX1 A9H ET0 Bit No. C0H C7H − C6H TF2 C5H IEX6 C4H IEX5 C3H IEX4 C2H IEX3 C1H IEX2 C0H IADC IRCON The shaded bits are not used in Timer/counter 2 interrupt control. Bit ET2 Function Timer 2 Overflow/External Reload Interrupt Enable If ET2 = 0, the timer 2 interrupt is disabled. If ET2 = 1, the timer 2 interrupt is enabled. Timer 2 Overflow Flag Set by a timer 2 overflow and must be cleared by software. If the Timer 2 interrupt is enabled, TF2 = 1 will cause an interrupt. TF2 User’s Manual 6-29 2001-05 C508 On-Chip Peripheral Components Special Function Register CCEN (Address C1H) Bit No. MSB 7 6 5 4 3 2 1 Reset Value: 00H LSB 0 CCEN C1H COCAH3 COCAL3 COCAH2 COCAL2 COCAH1 COCAL1 COCAH0 COCAL0 Bit COCAH3 COCAL3 Function Compare/Capture mode for CC register 3 COCAH3 COCAL3 Function 0 0 1 1 0 1 0 1 Compare/Capture disabled Capture on rising edge at pin P5.3 / T2CC3 / INT6 Compare enabled Capture on write operation into register CCL3 COCAH2 COCAL2 Compare/Capture mode for CC register 2 COCAH2 COCAL2 Function 0 0 1 1 0 1 0 1 Compare/Capture disabled Capture on rising edge at pin P5.2 / T2CC2 / INT5 Compare enabled Capture on write operation into register CCL2 User’s Manual 6-30 2001-05 C508 On-Chip Peripheral Components Bit COCAH1 COCAL1 Function Compare/Capture mode for CC register 1 COCAH1 COCAL1 Function 0 0 1 1 COCAH0 COCAL0 0 1 0 1 Compare/Capture disabled Capture on rising edge at pin P5.1 / T2CC1 / INT4 Compare enabled Capture on write operation into register CCL1 Compare/Capture mode for CRC register COCAH0 COCAL0 Function 0 0 1 1 0 1 0 1 Compare/Capture disabled Capture on falling/rising edge at pin P5.0 / T2CC0 / INT3 Compare enabled Capture on write operation into register CRCL User’s Manual 6-31 2001-05 C508 On-Chip Peripheral Components 6.2.2.2 Timer 2 Operation Timer 2, which is a 16-bit-wide register, operates as a timer with its count rate derived from the oscillator frequency. A prescaler offers the possibility of selecting a count rate of 1/3 or 1/6 of the oscillator frequency. Thus, the 16-bit timer register (consisting of TH2 and TL2) is either incremented in every machine cycle or in every second machine cycle. The prescaler is selected by bit T2PS in special function register T2CON. lf T2PS is cleared, the input frequency is 1/3 of the oscillator frequency. If T2PS is set, the 2:1 prescaler gates 1/6 of the oscillator frequency to the timer. The timer overflow flag TF2 in SFR IRCON is set when there is a roll-over of the count from all ‘1’s to all ‘0’s. The flag TF2 can generate an interrupt and it must be cleared by the interrupt service routine. User’s Manual 6-32 2001-05 C508 On-Chip Peripheral Components Reload of Timer 2 The reload mode for Timer 2 is selected by bits T2R0 and T2R1 in SFR T2CON. To enable the reload mode, bit T2R0 must be cleared and bit T2R1 set. Figure 6-14 shows the configuration of Timer 2 in reload mode. When Timer 2 rolls over from all ‘1’s to all ‘0’s, it not only sets TF2 but also causes the Timer 2 registers to be loaded with the 16-bit value in the CRC registers, which are preset by software. The reload will happen in the same machine cycle in which TF2 is set, thus overwriting the count value 0000H. Input Clock TL2 TH2 T2R0 = '0' and T2R1 = '1' Reload Timer 2 Interrupt Request CRCL CRCH TF2 MCS04055 Figure 6-14 Timer 2 in Reload Mode User’s Manual 6-33 2001-05 C508 On-Chip Peripheral Components 6.2.2.3 Compare Function of Registers CRC, T2CC1 to T2CC3 The compare function of a timer/register combination can be described as follows. The 16-bit value stored in a Compare/Capture register is compared with the contents of the timer register. lf the count value in the timer register matches the stored value, an appropriate output signal is generated at a corresponding port pin, and an interrupt is requested. The contents of a compare register can be regarded as a “time stamp” at which a dedicated output reacts in a predefined way (with either a positive or negative transition). Variation of this “time stamp” somehow changes the wave of a rectangular output signal at a port pin. As a variation of the duty cycle of a periodic signal, this may be used for pulse width modulation as well as for a continually controlled generation of any kind of square waveforms. Two Compare modes are implemented to cover a wide range of possible applications. The compare modes 0 and 1 are selected by bit T2CM in special function register T2CON. In both compare modes, the new value arrives at the port pin 1 within the same machine cycle in which the internal compare signal is activated. The four registers CRC, T2CC1 to T2CC3 are multifunctional as they additonally provide a capture, compare or reload capability (reload capability for CRC register only). A general selection of the function is done in register CCEN. Please note that the compare interrupt CC0 can be programmed to be negative or positive transition activated. The internal compare signal (not the output signal at the port pin!) is active as long as the timer 2 contents is equal to the one of the appropriate compare registers, and it has a rising and a falling edge. Thus, when using the CRC register, it can be selected whether an interrupt should be caused when the compare signal goes active or inactive, depending on bit I3FR in T2CON. For the CC registers 1 to 3 an interrupt is always requested when the compare signal goes active (see Figure 6-16). 6.2.2.3.1 Compare Mode 0 In mode 0, when the timer and compare register contents match, the output signal changes from low to high. lt goes back to a low level on timer overflow. As long as compare mode 0 is enabled, the appropriate output pin is controlled by the timer circuit only, and not by the user. Writing to the port will have no effect. Figure 6-15 shows a functional diagram of a port latch in compare mode 0. The port latch is directly controlled by the two signals timer overflow and compare. The input line from the internal bus and the write-to-latch line are disconnected when compare mode 0 is enabled. Compare mode 0 is ideal for generating pulse width modulated output signals, which in turn can be used for digital-to-analog conversion via a filter network or by the controlled device itself (e.g. the inductance of a DC or AC motor). Mode 0 may also be used for providing output clocks with initially defined period and duty cycle. This is the mode which needs the least CPU time. Once set up, the output goes on oscillating without any User’s Manual 6-34 2001-05 C508 On-Chip Peripheral Components CPU intervention. Figure 6-16 and Figure 6-17 illustrate the function of compare mode 0. Compare Register Circuit Compare Reg. Port Circuit Read Latch VDD 16-Bit Internal Bus Comparator Compare Match Write to Latch S D Q Port Pin Port Latch CLK Q R 16-Bit Timer Register Timer Circuit Timer Overflow Read Pin MCS04056 Figure 6-15 Port Latch in Compare Mode 0 I3FR IEXx Compare Register CCx 16-Bit Comparator Interrupt Shaded function for CRC only Set Latch Compare Signal Reset Latch R Overflow Q SR Q SR Q SR Q S 16-Bit TH2 TL2 Timer 2 P5.3/ P5.2/ P5.1/ P5.0/ T2CC3/ T2CC2/ T2CC1/ T2CC0/ Interrupt INT6 INT5 INT4 INT3 (CCx stands for CRC, T2CC1 to T2CC3, IEXx stands for IEX3 to IEX6) MCS04057 Figure 6-16 Timer 2 with Registers CCx in Compare Mode 0 User’s Manual 6-35 2001-05 C508 On-Chip Peripheral Components Timer Count = FFFF H Timer Count = Compare Value Contents of Timer 2 Timer Count = Reload Value Interrupt can be generated on overflow Compare Output (P5.x/T2CCx) Interrupt can be generated on compare-match MCD04058 Figure 6-17 Function of Compare Mode 0 6.2.2.3.2 Modulation Range of a PWM Signal in Compare Mode 0 Generally, it can be said that for every PWM generation in compare mode 0 with n-bit wide compare registers there are 2n different settings for the duty cycle. Starting with a constant low level (0% duty cycle) as the first setting, the maximum possible duty cycle would then be: (1 - 1/2n) × 100% This means that a variation of the duty cycle from 0% to real 100% can never be reached if the compare register and timer register have the same length. There is always a spike which is as long as the timer clock period. This “spike” may either appear when the compare register is set to the reload value (limiting the lower end of the modulation range) or it may occur at the end of a timer period. This spike in CCx register configuration of timer 2 in compare mode 0 is divided into two halves. One half is at the beginning when the contents of the compare register are equal to the reload value of the timer and the other half is when the compare register is equal to the maximum value of the timer register (that is, FFFFH). Refer to Figure 6-18 where the maximum and minimum duty cycles of a compare output signal are illustrated. User’s Manual 6-36 2001-05 C508 On-Chip Peripheral Components Timer 2 is incremented with every machine clock (fOSC/6); thus, both these spikes are approximately 150 ns long at 20-MHz operational frequency. a) CCHx/CCLx = 0000 H or = CRCH/CRCL (maximum duty cycle) P5.x H L Appr.1/2 Machine Cycle b) CCHx/CCLx = FFFF H (minimum duty cycle) P5.x H L Appr.1/2 Machine Cycle MCD04059 Figure 6-18 PWM Signal Modulation Range (generated with a Timer 2/CCx Register Combination in Compare Mode 0*) The following illustrates the calculation of The modulation range for a PWM signal. To calculate with reasonable numbers, a reduction of the resolution to 8-bit is used. Otherwise (for the maximum resolution of 16-bit) the modulation range would be so severely limited that it would be negligible. Example: Case: Timer 2 in auto-reload mode. Contents of reload register CRC = FF00H Restriction of modulation range = 1 / (256 × 2) × 100% = 0.195% This leads to a variation of the duty cycle from 0.195% to 99.805% for a timer 2/CCx register configuration when 8 of the 16 bits are used. User’s Manual 6-37 2001-05 C508 On-Chip Peripheral Components 6.2.2.3.3 Compare Mode 1 In compare mode 1, the software adoptively determines the transition of the output signal. lt is commonly used when output signals are not related to a constant signal period (as in a standard PWM Generation) but must be controlled very precisely with high resolution and without jitter. In compare mode 1, both transitions of a signal can be controlled. Compare outputs in this mode can be regarded as high speed outputs which are independent of the CPU activity. lf compare mode 1 is enabled and the software writes to the appropriate output latch at the port, the new value will not appear at the output pin until the next compare match occurs. Thus, one can choose whether the output signal is to make a new transition (1to-0 or 0-to-1, depending on the actual pin level) or should keep its old value at the time the Timer 2 count matches the stored compare value. Figure 6-19 and Figure 6-20 show functional diagrams of the timer/compare register/ port latch configuration in compare mode 1. In this function, the port latch consists of two separate latches. The upper latch (which acts as a “shadow latch”) can be written under software control, but its value will only be transferred to the output latch (and thus to the port pin) in response to a compare match. Note that the double latch structure is transparent as long as the internal compare signal is active. While the compare signal is active, a write operation to the port will then change both latches. This may become important when driving Timer 2 with a slow external clock. In this case the compare signal could be active for many machine cycles in which the CPU could unintentionally change the contents of the port latch. A read-modify-write instruction will read the user-controlled “shadow latch” and write the modified value back to this “shadow-latch”. A standard read instruction will read the pin of the corresponding compare output, as usual. User’s Manual 6-38 2001-05 C508 On-Chip Peripheral Components Compare Register Circuit Compare Reg. Read Latch Port Circuit VDD 16-Bit Internal Bus Compare Match Write to Latch D Shadow Latch CLK Q D Port Latch CLK Q Q Port Pin Comparator 16-Bit Timer Register Timer Circuit Read Pin MCS04060 Figure 6-19 Port Latch in Compare Mode 1 User’s Manual 6-39 2001-05 C508 On-Chip Peripheral Components I3FR IEXx Compare Register CCx 16-Bit Comparator Interrupt Shaded function for CRC only Port Latch Circuit Compare Signal Shadow Latch 16-Bit TH2 TL2 Overflow Interrupt Output Latch Timer 2 P5.7 P5.3/ T2CC3/ INT6 P5.0/ T2CC0/ INT3 MCS04061 ... (CCx stands for CRC, T2CC1 to T2CC3, IEXx stands for IEX3 to IEX6) Figure 6-20 Timer 2 with Registers CCx in Compare Mode 1 User’s Manual 6-40 2001-05 C508 On-Chip Peripheral Components 6.2.2.4 Using Interrupts in Combination with the Compare Function The compare service of registers CRC, T2CC1, T2CC2 and T2CC3 are assigned to alternate output functions at port pins P5.0 to P5.3. Another option of these pins is that they can be used as external interrupt inputs. However, when using the port lines as compare outputs then the input line from the port pin to the interrupt system is disconnected (but the pin’s level can still be read under software control). Thus, a change of the pin’s level will not cause a setting of the corresponding interrupt flag. In this case, the interrupt input is directly connected to the (internal) compare signal thus providing a compare interrupt. The compare interrupt can be used very effectively to change the contents of the compare registers or to determine the level of the port outputs for the next “compare match”. The principle is that the internal compare signal (generated at a match between timer count and register contents) not only manipulates the compare output but also sets the corresponding interrupt request flag. Thus, the current task of the CPU is interrupted if the priority of the Compare interrupt is higher than the present task priority and the corresponding interrupt service routine is called. This service routine then sets up all the necessary parameters for the next compare event. Advantages when Using Compare Interrupts First, there is no danger of unintentional overwriting a Compare register before a match has been reached. This could happen when the CPU writes to the compare register without knowing about the actual Timer 2 count. Second, and the most interesting advantage of the compare feature, is that the output pin is exclusively controlled by hardware; therefore, it is completely independent from any service delay which in real time applications could be disastrous. The compare interrupt in turn is not sensitive to such delays since it loads the parameters for the next event. This in turn is supposed to happen after a sufficient amount of time. Please note the following special case where a program using compare interrupts could show a “surprising” behavior. The configuration has already been mentioned in the description of compare mode 1. The fact that the compare interrupts are transition activated becomes important when driving Timer 2 with a slow external clock. In this case it should be carefully considered that the compare signal is active as long as the Timer 2 count is equal to the contents of the corresponding compare register, and that the compare signal has a rising and a falling edge. Furthermore, the “shadow latches” used in compare mode 1 are transparent while the compare signal is active. Thus, with a slow input clock for Timer 2, the comparator signal is active for a long time (i.e. high number of machine cycles) and therefore a fast interrupt controlled reload of the compare register could not only change the “shadow latch” - as probably intended but also the output buffer. User’s Manual 6-41 2001-05 C508 On-Chip Peripheral Components When using the CRC, an interrupt should be generated when the compare signal goes active or inactive, depending on the status of bit I3FR in T2CON. Initializing the interrupt to be negative transition triggered is advisable in the above case. Then the compare signal is already inactive and any write access to the port latch changes only the contents of the “shadow-latch”. Note that for T2CC1 to T2CC3 registers, an interrupt is always requested when the compare signal goes active. The second configuration which should be noted is the compare function combined with negative transition activated interrupts. lf the port latch of Port P5.0 contains a ‘1’, the interrupt request flags IEX3 will immediately be set after enabling the compare mode for the CRC register. The reason is that first the external interrupt input is controlled by the pin’s level. When the compare option is enabled, the interrupt logic input is switched to the internal compare signal, which carries a low level when no true comparison is detected. So, the interrupt logic sees a 1-to-0 edge and sets the interrupt request flag. An unintentional generation of an interrupt during compare initialization can be prevented if the request flag is cleared by software after the compare is activated and before the external interrupt is enabled. User’s Manual 6-42 2001-05 C508 On-Chip Peripheral Components 6.2.2.5 Capture Function Each of the Compare/Capture registers T2CC1 to T2CC3 and the CRC register can be used to latch the current 16-bit value of the Timer 2 registers TL2 and TH2. Two different modes are provided for this function. In mode 0, an external event latches the Timer 2 contents to a dedicated capture register. In mode 1, a capture will occur upon writing to the low order byte of the dedicated 16-bit capture register. This mode allows the software to read the contents of Timer 2 “on-the-fly”. In mode 0, the external event causing a capture is: – For T2CC registers 1 to 3: a positive transition at pins T2CC1 to T2CC3 of Port 5 – For the CRC register: a positive or negative transition at the corresponding pin, depending on the status of the bit I3FR in SFR T2CON. lf the edge flag is cleared, a capture occurs in response to a negative transition. lf the edge flag is set, a capture occurs in response to a positive transition at pin P5.0 / T2CC0 / INT3. In both cases, the appropriate Port 5 pin is used as input and the port latch must be programmed to contain a one (1). The external input is sampled in every machine cycle. When the sampled input shows a low (high) level in one cycle and a high (low) in the next cycle, a transition is recognized. The Timer 2 contents are latched to the appropriate capture register in the cycle following the one in which the transition was identified. In mode 0: a transition at the external capture inputs of registers T2CC1 to T2CC3 will also set the corresponding external interrupt request flags IEX4 to IEX6. lf the interrupts are enabled, an external capture signal will cause the CPU to vector to the appropriate interrupt service routine. In mode 1: a capture occurs in response to a write instruction to the low order byte of a capture register. The write-to-register signal (example, write-to-CRCL) is used to initiate a capture. The value written to the dedicated capture register is irrelevant for this function. The Timer 2 contents will be latched into the appropriate capture register in the cycle following the write instruction. In this mode no interrupt request will be generated. Figure 6-21 illustrates the operation of the CRC register, while Figure 6-22 shows the operation of the Compare/Capture registers 1 to 3. The two capture modes can be established individually for each capture register by bits in SFR CCEN (Compare/Capture enable register). That means, in contrast to the compare modes, it is possible to simultaneously select mode 0 for one capture register and mode 1 for another register. User’s Manual 6-43 2001-05 C508 On-Chip Peripheral Components Input Clock TL2 TH2 TF2 Timer 2 Interrupt Request Write to CRCL Mode 1 T2CON.6 Mode 0 Capture CRCL CRCH External Interrupt 3 Request MCS04062 P5.0/ T2CC0/ INT3 IEX3 Figure 6-21 Timer 2 – Capture with Register CRC Input Clock TL2 TH2 TF2 Timer 2 Interrupt Request Write to CCL1 Mode 1 Mode 0 Capture T2CCL1 P5.1/ T2CC1/ INT4 T2CCH1 External Interrupt 4 Request MCS04063 IEX4 Figure 6-22 Timer 2 – Capture with Registers T2CC1 to T2CC3 User’s Manual 6-44 2001-05 C508 On-Chip Peripheral Components 6.3 Capture/Compare Unit (CCU) The Capture/Compare Unit (CCU) of the C508 has been designed for applications which demand digital signal generation and/or event capturing (such as pulse width modulation or pulse width measuring). It consists of a 16-bit three-channel Capture/Compare unit (CAPCOM) and a 10-bit one-channel Compare unit (COMP). In compare mode, the CAPCOM unit provides two output signals per channel, which can have inverted signal polarity and non-overlapping pulse transitions. The COMP unit can generate a single PWM output signal and is further used to modulate the CAPCOM output signals. For motor control applications, both units (CAPCOM and COMP) may generate versatile multichannel PWM signals. For brushless DC motors, dedicated control modes are supported which are controllable by either software or hardware (hall sensors). 16-Bit Capture/Compare Unit (CAPCOM) Period Register (CCPH, CCPL) Mode Select Register (CMSEL0, CMSEL1) Trap/Initialization Registers (COINI, COTRAP, TREN) CTRAP Prescaler Offset Register (CT1OFH,CT1OFL) CC Channel 0 (CCH0, CCL0) CC0 COUT0 Port Control Logic CC1 COUT1 CC2 COUT2 2fOSC Control Compare Timer 1 (16-Bit) CC Channel 1 (CCH1, CCL1) CC Channel 2 (CCH2, CCL2) Cntrl. Register (CT1CON) 10-Bit Compare Unit (COMP) Period Register (CP2H, CP2L) Prescaler 2fOSC Compare Timer 2 (10-Bit) Compare Reg. (CMP2H, CMP2L) Block Commutation Control (BCON) COUT3 Cntrl. Register (CT2CON) INT0 INT1 INT2 MCB04064 Figure 6-23 Capture/Compare Unit Block Diagram User’s Manual 6-45 2001-05 C508 On-Chip Peripheral Components 6.3.1 General Capture/Compare Unit Operation The Compare Timer 1 and 2 are free running, processor clock coupled 16-bit/10-bit timers; each of which has a count rate with a maximum of 2 fOSC up to fOSC/64. The compare timer operations with its possible compare output signal waveforms are shown in Figure 6-24. Compare Timer 1 Operating Mode 0 a) Standard PWM (Edge Aligned) b) Standard PWM (Single Edge Aligned) with programmable dead time ( tOFF ) Period Value Compare Value 0000H Period Value Compare Value Offset { tOFF CCx COUTx CCx COUTx Compare Timer 1 Operating Mode 1 c) Symmetrical PWM (Center Aligned) d) Symmetrical PWM (Center Aligned) with programmable dead time ( tOFF ) Period Value Compare Value 0000H Period Value Compare Value Offset { tOFF tOFF CCx COINI=0 COUTx COINI=1 : Interrupt can be generated CCx COINI=0 COUTx COINI=1 MCD04065 Figure 6-24 CAPCOM Unit Basic Operating Modes User’s Manual 6-46 2001-05 C508 On-Chip Peripheral Components Both compare timers start counting from 0000H upwards to a count value stored in the period registers. If the value stored in the period register is reached, they are reset (operating mode 0, both compare timers) or the count direction is changed from upcounting to down-counting (operating mode 1, only Compare Timer 1) Using operating mode 0, edge aligned PWM signals can be generated. Using operating mode 1, center aligned PWM signals can be generated. Compare Timer 1 can be programmed for both operating modes while Compare Timer 2 always works in operating mode 0 with one output signal COUT3. Figure 6-24 a) and c) show the function of these basic operating modes. Compare Timer 1 has an additional 16-bit offset register, which consists of the high byte stored in CT1OFH and the low byte stored in CT1OFL. If the value stored in CT1OFF is 0, the compare timer operates as shown in Figure 6-24 a) and c). If the value stored in CT1OFF is not zero, the compare timer operates as shown in Figure 6-24 b) and d). In operating mode 0, Compare Timer 1 is always reset after its value has been equal to the value stored in period register. In operating mode 1, the count direction of the compare timer is changed from up- to down-counting when its value has reached the value stored in the period register. The count direction is changed from down- to up-counting when the compare timer value has reached 0000H. Generally, the compare outputs CCx are always assigned to a match condition with the compare timer value directly, where as the compare outputs COUTx are assigned to a match condition with the compare timer value plus the offset value. Therefore, signal waveforms with non-overlapping signal transitions as shown in Figure 6-24 b) and d) can be generated. Further, the initial logic output level of the CAPCOM channel outputs can be selected in compare mode. This allows waveforms to be generated with inverting signal polarities. In capture mode of the CAPCOM unit, the value of Compare Timer 1 is stored in the capture registers on a signal transition at pins CCx. The compare unit COMP is a 10-bit compare unit which can be used to generate a Pulse Width Modulated signal. This PWM output signal drives the output pin COUT3. In burst mode and in the PWM modes, the output of the COMP unit can be switched to the COUTx outputs. The block commutation control logic allows to generate versatile multi-channel PWM output signals. In one of these modes, the block commutation mode, signal transitions at the three external interrupt inputs are used to trigger the PWM signal generation logic. Depending on these signal transitions, the six I/O lines of the CAPCOM unit, which are decoupled in block commutation mode from the three Capture/Compare channels, are driven as static or PWM modulated outputs. CAPCOM channel 0 can be used in block commutation mode for a capture operation (speed measurement) which is triggered by each transition at the external interrupt inputs. Further, the multi-channel PWM mode signal generation can be also triggered by the period of Compare Timer 1. These operating modes are referenced as multi-channel PWM modes. User’s Manual 6-47 2001-05 C508 On-Chip Peripheral Components Using the CTRAP input signal of the C508, the compare outputs can be put immediately into their state as defined in COTRAP register. The CCU unit has four main interrupt sources with their specific interrupt vectors. Interrupts can be generated at the Compare Timer 1 period match or count-change events, at the Compare Timer 2 period match event, at a CAPCOM Compare match or Capture event, and at a CAPCOM emergency event. An emergency event occurs if an active CTRAP signal is detected or if an error condition in block commutation mode is detected. All interrupt sources can be enabled/disabled individually. User’s Manual 6-48 2001-05 C508 On-Chip Peripheral Components 6.3.2 6.3.2.1 CAPCOM Unit Operation CAPCOM Unit Clocking Scheme The CAPCOM unit is controlled by the 16-bit Compare Timer 1. Compare Timer 1 is the timing base for all compare and capture capabilities of the CAPCOM unit. The input clock for Compare Timer 1 is directly coupled to the system clock of the C508. Its frequency can be selected via three bits of the CT1CON register in a range of 2 fOSC up to fOSC/64. For the understanding of the following timing diagrams, Figure 6-25 shows the internal clocking scheme of the CAPCOM unit. The internal input clock of the CAPCOM unit is a symmetrical clock with 50% duty cycle. The clock transitions (edges) of the CAPCOM internal input clock are used for different actions. At clock edge 1, the Compare Timer 1 is clocked to the next count value and with clock edge 2, the compare outputs CCx and COUTx are toggled/set to the new logic level if required. Input clock of CT1 2fOSC 1 2 min. 50 ns (@ 10 MHz oscillator clock) 1 2 fOSC 1 2 fOSC /2 1 2 fOSC /4 1 increment/decrement of compare timer 1 2 change/modify logic level at CCx/COUTx MCD04066 Figure 6-25 CAPCOM Unit Clocking Scheme Generally, the CAPCOM clocking scheme shown above is also valid for the COMP (Compare Timer 2) unit. User’s Manual 6-49 2001-05 C508 On-Chip Peripheral Components 6.3.2.2 CAPCOM Unit Operating Mode 0 Figure 6-26 shows the details of the CAPCOM unit timing in operating mode 0. CT1 Value CCP = 7 Period Reg. 4 Offset Reg. CT1OFF = 0 1 0 Start of CT1 (CC = 0) 0 3 2 1 0 2 1 3 2 Time Duty Cycles: 100% 7 6 5 4 3 5 4 6 7 CCx or COUTx COINI bit is "0" (active high signals) (CC = 1) (CC = 4) (CC ≥ 7) (CC = 0) "0" 87.5% 50% 0% 100% 87.5% 50% "1" 0% CCx or COUTx COINI bit is "1" (active low signals) (CC = 1) (CC = 4) (CC ≥ 7) CC : content of the CCxH/CCxL compare registers CCP : content of the CCPH/CCPL period register CC1O : content of the CT1OFH/CT1OFL offset register MCT04067 Figure 6-26 Compare Timer 1 Mode 0 In the example above, Compare Timer 1 counts from 0000H up to 0007H (value stored in CCPH/CCPL). The offset registers CT1OFH/CT1OFL have a value of 0000H. If programmed in compare mode, two output signals (CCx and COUTx) are assigned to the related CAPCOM channel x. The mode select bits in the SFRs CMSEL0 and User’s Manual 6-50 2001-05 C508 On-Chip Peripheral Components CMSEL1 define which of these two outputs will be controlled by the CAPCOM channel. In Figure 6-26 only the CCx signal is shown, but the same or the inverted waveform can be generated at the COUTx outputs. After reset all CCx/COUTx pins are at high level, driven by a weak pull-up. With the programming of the CMSEL1 or CMSEL0 registers, all affected compare outputs are switched to push-pull mode and start driving an initial level which is defined by the bits in SFR COINI. In Figure 6-26, the upper five waveforms are assigned to a CCx pin with the appropriate bit in COINI cleared while the lower five waveforms are assigned to a CCx pin with the appropriate bit in COINI set. When the count value of the Compare Timer 1 is incremented and the new value matches the value stored in the corresponding compare register, the related compare output changes its logic state. When the compare timer is reset to 0000H the related compare output changes its logic state again. With the scheme shown in Figure 6-26, output waveforms with duty cycles between 0% and 100% can be generated. For a compare register value of 0000H, the output will remain at high level (COINI bit = 0) or low level (COINI bit = 1), representing a duty cycle of 100%. If the value stored in the compare register is greater than or equals to the value of the period register, a low level (COINI bit = 0) or high level (COINI bit = 1) corresponds to a duty cycle of 0%. Figure 6-27 shows the waveform generation in operating mode 0 when the offset register has a value which is not equal 0000H (example: CT1OFH/CT1OFL = 0002H). Using Compare Timer 1 with an offset value not equal 0 is used to generate single edge aligned signals with a constant delay between one of the two signal transitions. Compare Timer 1 always counts from 0000H up to the value stored in CCP, if the value in the offset register is not equal 0. With reset (count value 0000H) of the Compare Timer 1, the CCx and COUTx will always change their logic state. During the up-counting phase, CCx will change the logic state when the compare timer value is equal to the compare register value; and COUTx will change the logic state when the compare timer value plus the offset value matches the value stored in the compare register. In Figure 6-27 the waveforms a) and b) show an example for a waveform of two signals with a constant delay of their rising edge. A compare register value of 3 is assumed. Using inverted signal polarity (SFR COINI), signal c) can be generated at COUTx. If the value in the offset register plus the value of the period register is less than or equal to the value stored in the compare register, a static ‘1’ or a static ‘0’ (depending on COINI content) will be generated at COUTx (see Figure 6-27 d) and e)). Therefore, CCx will also stay at a static level if the compare register value is greater than the value stored in the period register. User’s Manual 6-51 2001-05 C508 On-Chip Peripheral Components Count Value 9 CCP = 7 Period Reg. 6 5 4 3 CT1OF = 2 Offset Reg. Start of CT1 CC 3 3 3 > CT1OF + CCP = CT1OF COINI Pin 0 0 1 0 0 CCx COUTx COUTx COUTx COUTx "0" 2 1 0 t OFF 0 2 3 4 CT1 3 2 1 5 8 7 6 7 CT1+CT1OFF 9 8 7 6 5 4 3 2 4 CT1 3 2 1 0 t OFF t OFF Time 2 5 4 3 6 5 4 7 6 a) b) c) 0% 100% d) e) CC : content of the CCxH/CCxL compare registers CCP : content of the CCPH/CCPL period register CT1OF : content of the CT1OFH/CT1OFL offset registers MCT04293 Figure 6-27 Compare Timer 1 with Offset not equal 0 – Mode 0 User’s Manual 6-52 2001-05 C508 On-Chip Peripheral Components 6.3.2.3 CAPCOM Unit Operating Mode 1 Using Compare Timer 1 in operating mode 1, two symmetric output signals with constant dead time tOFF at each signal transition can be generated per channel. Figure 6-28 shows the operating mode 1 timing in detail. Count Value 9 CCP = 7 Period Reg. 6 5 4 3 CT1OF = 2 Offset Reg. Start of CT1 CCx (CC = 5) COINI Bit = 0 COUTx (CC = 5) COINI Bit = 0 COUTx (CC = 5) COINI Bit = 1 CC : content of the CCxH/CCxL compare registers CCP : content of the CCPH/CCPL period register CT1OF : content of the CT1OFH/CT1OFL offset registers 2 1 0 t OFF t OFF 2 3 4 5 CT1 8 7 6 7 6 5 4 3 2 1 0 t OFF 8 7 6 5 4 3 2 1 Time Duty Cycles: 29% 57% 57% 3 2 4 3 5 4 6 5 7 CT1+CT1OFF MCT04294 Figure 6-28 Compare Timer 1 with Offset not equal to 0 - Mode 1 In the example above, Compare Timer 1 counts from 0000H up to 0007H (value stored in period register CCPH/CCPL) and then counts down again to 0000H. The maximum and minimum (0000H) values of the Compare Timer 1 always occur once in the count value sequence. In the example shown in Figure 6-28, the offset registers have a value of 0002H. With the programming of the CMSEL1 or CMSEL0 registers, all affected compare outputs are switched to push-pull mode and start driving an initial level defined by the bits in SFR COINI. In operating mode 0, two compare output signals, CCx and COUTx, are assigned to the related CAPCOM channel. The compare outputs CCx change their state if a match of Compare Timer 1 content and the corresponding compare register occurs. The compare outputs COUTx change their state when a match of Compare Timer 1 content plus the value stored in the offset registers and the corresponding compare register has occurred. If the value in the offset register plus the value of the period register is less than or equal to the value stored in the compare register, a static ‘1’ or a static ‘0’ (depending User’s Manual 6-53 2001-05 C508 On-Chip Peripheral Components on COINI content) will be generated at COUTx. In the same way, CCx will also stay at a static level if the compare register value is greater than the value stored in the period register. 6.3.2.4 CAPCOM Unit Timing Relationships Depending on the operating mode of the Compare Timer 1, compare output signals can be generated with a maximum period and resolution as shown in Figure 6-29. This example also demonstrates the reloading of the compare and period registers which occurs when Compare Timer 1 reaches the count value 0000H. User’s Manual 6-54 2001-05 C508 On-Chip Peripheral Components Operating Mode 0: Count Value Load Reg. with CCxReg. = 2 CCP = 3 1 Load Reg. with CCxReg. = 2 CCP = 5 2 4 Start of CT1 CCxReg. = 1 CCP = 2 0 CCx/ COUTx min. 150 ns (@ 10 MHz clock rate) Operating Mode 1: Count Value Load Reg. with CCxReg. = 1 CCP = 4 1 4 Start of CT1 CCxReg. = 1 CCP = 2 0 CCx/ COUTx min. 200 ns (@ 10 MHz clock rate) 3 2 1 1 0 1 2 1 0 1 2 3 2 1 0 1 2 Time 3 3 2 1 0 1 0 2 1 0 2 1 0 2 1 3 2 Time 3 5 MCT04068 Figure 6-29 Maximum Period and Resolution of the Compare Timer 1 Unit Figure 6-29 shows the resolution and the period value range which depends on the selected Compare Timer 1 input clock prescaler ratio. User’s Manual 6-55 2001-05 C508 On-Chip Peripheral Components Table 6-6 Compare Timer 1 Input Clock 2 fOSC Resolution and Period of the Compare Timer 1 (at fOSC = 10 MHz) Operating Mode 0 Resolution 50 ns 100 ns 200 ns 400 ns 800 ns 1.6 µs 3.2 µs 6.4 µs Period 100ns - 3.28 ms 200 ns - 6.55 ms 400 ns - 13.11 ms 800 ns - 26.21 ms 1.6 µs - 52.43 ms 3.2 µs - 104.86 ms 6.4 µs - 209.72 ms 12.8 µs - 419.43 ms Operating Mode 1 Resolution 50 ns 100 ns 200 ns 400 ns 800 ns 1.6 µs 3.2 µs 6.4 µs Period 200 ns - 6.55 ms 400 ns - 13.11 ms 800 ns - 26.21 ms 1.6 µs - 52.43 ms 3.2 µs - 104.86 ms 6.4 µs - 209.71 ms 12.8 µs - 419.42 ms 25.6 µs - 838.85 ms fOSC fOSC / 2 fOSC / 4 fOSC / 8 fOSC / 16 fOSC / 32 fOSC / 64 Compare Timer 1 period and duty cycle values can be calculated using the formulas given below. Following abbreviations are used. pv = period value, stored in the period registers CCPH/CCPL ov = offset value, stored in the offset registers CT1OFH/CT1OFL cv = compare value, stored in the Capture/Compare registers CCHx/CCLx Operating Mode 0: Period value = pv + 1 Duty cycle of CCx outputs = Duty cycle of COUTx outputs = 1_ cv × 100% pv + 1 cv - ov 1_ pv + 1 × 100% Operating Mode 1: Period value = 2 × pv Duty cycle of CCx outputs = 1_ cv pv × 100% × 100% cv - ov Duty cycle of COUTx outputs = 1 _ pv User’s Manual 6-56 2001-05 C508 On-Chip Peripheral Components 6.3.2.5 Burst Mode of CAPCOM / COMP Unit In burst mode, both units of the CCU are combined in a way that the CAPCOM outputs COUTx or CCx and COUTx (controlled by bit BCMP in SFR BCON) are modulated by the output signal of the COMP unit. Using the burst mode, the CAPCOM unit operates in compare mode and the COMP unit provides a PWM signal which is switched to the COUTx outputs. This PWM signal typically has a higher frequency than the compare output signal of the CAPCOM unit. Figure 6-30 shows the waveform generation using the burst mode. Count Value Period Register Compare Register Start of CT1 Time COUTx (COINI = 1) COUTx (COINI = 0) Compare Timer 2 COUT3 COUT3I = 0 COUTXI = 0 COUT3I = 0 COUTXI = 1 COUT3I = 1 COUTXI = 1 COUT3I = 1 COUTXI = 0 Note: If the Bits COUT3I and COUTXI in the COINI register are identical, COUT3 and the burst signals at COUTx have the same polarity. MCT04295 Compare Timer 1 (CT1OFF = 0) CMSELx3 = 0 Burst Mode Disabled COUTx (COINI = 1) COUTx (COINI = 0) Figure 6-30 Burst Mode Operation User’s Manual 6-57 2001-05 C508 On-Chip Peripheral Components Burst mode of a COUTx output is enabled by the bit CMSELx3, located in the mode select registers CMSEL0 and CMSEL1. Figure 6-30 shows four CAPCOM output signals with different initial logic states with burst mode disabled (CMSELx3 = 0) and burst mode enabled (CMSELx3 = 1). Generally, the CCx outputs cannot operate in burst mode. Optionally, the signal at COUTx may have inverted polarity than the PWM signal which is available at pin COUT3. Depending on the corresponding initial compare output level bit in COINI, either a low or high level for the non-modulated state at the COUTx pins can be selected. Burst mode can be enabled in both operating modes of the Compare Timer 1. The burst mode as shown in Figure 6-30 is only valid if the block commutation mode of the CCU is disabled (bit BCEN of SFR BCON cleared). Modulation of the compare output signals at COUTx is switched on (COUT3 signal is switched to COUTx) when the Compare Timer 1 contents plus the value stored in the Compare Timer 1 offset register are equal to or greater than the value stored in the compare register of CAPCOM channel x. 6.3.2.6 CAPCOM Unit in Capture Mode The three channels of the CAPCOM unit can be individually programmed to operate in capture mode. In capture mode, each CAPCOM channel offers one capture input at pin CCx. Compare Timer 1 runs either in operating mode 0 or 1. A rising or/and falling edge at CCx will copy the actual value of the Compare Timer 1 into the Compare/Capture registers. Interrupts can be generated selectively at each transition of the capture input signal. Capture mode is selected by writing the mode select registers CMSEL1 and CMSEL0 with the appropriate values. The bit combinations in CMSEL0 and CMSEL1 also define the signal transition type (falling/rising edge) which generates a capture event. If a CAPCOM channel is enabled for capture mode, its CCx input is sampled with 1/(4 TCL) (i.e. 2 fOSC = twice external oscillator clock rate). Consecutive capture events, generated through signal transitions at a CCx capture input, overwrite the corresponding 16-bit Compare/Capture register contents. This must be considered when successive signal transitions are processed. User’s Manual 6-58 2001-05 C508 On-Chip Peripheral Components 6.3.2.7 Trap Function of the CAPCOM Unit in Compare Mode When a channel of the CAPCOM unit operates in compare mode, its output lines can be decoupled in trap mode from the CAPCOM pulse generation. The trap mode is controlled by the external signal CTRAP. The CTRAP signal is sampled at each phase of the oscillator clock cycle. If a low is detected, the trap flag TRF of register TRCON is set and CCx or COUTx compare outputs are switched immediately to the logic state as defined by the bits in COTRAP if that particular channel has been enabled for trap function. The compare outputs of the channels which are not enabled for trap function will have their last output levels maintained. For safety reasons, it is recommended that trap function be enabled. If CT1RES = 0, Compare Timer 1 continues its operation but no compare output signal will be generated. If CT1RES = 1, Compare Timer 1 is reset when CTRAP becomes active. When CTRAP is sampled inactive (high) again, the compare channel outputs are synchronously switched to the compare channel output signal generation when Compare Timer 1 has reached the count value 0000H. The trap function is controlled by bits in the TRCON register. The general enable function of the external CTRAP signal is controlled by one bit (TRPEN). Further, each CAPCOM compare channel output can be enabled/disabled selectively for trap function. Figure 6-31 shows the trap function for the two outputs CCx and COUTx of one compare channel x. The timing diagram implies that the trap function is enabled at the CCx and COUTx outputs. At reference point 1) in Figure 6-31 CTRAP becomes active and at reference point 2) the trap state is released again synchronously to the Compare Timer 1 count state 0000H. If the trap function is enabled and CTRAP becomes active, bit TRF (trap flag) in SFR TRCON is set and a CCU emergency interrupt will be generated if the related interrupt enable bits are set. The flag TRF is level sensitive and must be cleared by software. The trap function used in block commutation mode differs from the trap function described above. In particular, the synchronization scheme is different (see Chapter 6.3.4.6). User’s Manual 6-59 2001-05 C508 On-Chip Peripheral Components a) Trap Function in CAPCOM Operating Mode 0 Period Value Compare Value Offset 2) CCx Trap State CT1+CT1OFF CT1 COUTx 1) CTRAP Trap State b) Trap Function in CAPCOM Operating Mode 1 Period Value Compare Value Offset 2) CCx COUTx 1) CTRAP MCT04296 CT1+CT1OFF CT1 Trap State Trap State . Note: The state of the CCx and COUTx signals in trap state is defined by the corresponding bits in COTRAP Figure 6-31 Trap Function of the CAPCOM Unit User’s Manual 6-60 2001-05 C508 On-Chip Peripheral Components 6.3.2.8 CAPCOM Registers The CAPCOM unit of the C508 contains several special function registers. Table 6-7 provides an overview of the CAPCOM related registers. Table 6-7 Unit CAPCOM Capture / Compare Unit Special Function Registers of the CAPCOM Unit Symbol CT1CON CCPL CCPH CT1OFL CT1OFH CMSEL0 CMSEL1 CCL0 CCH0 CCL1 CCH1 CCL2 CCH2 CCIR CCIE COINI TRCON COTRAP Description Compare Timer 1 Control Register Compare Timer 1 Period Register, Low Byte Compare Timer 1 Period Register, High Byte Compare Timer 1 Offset Register, Low Byte Compare Timer 1 Offset Register, High Byte Capture/Compare Mode Select Register 0 Capture/Compare Mode Select Register 1 Capture/Compare Register 0, Low Byte Capture/Compare Register 0, High Byte Capture/Compare Register 1, Low Byte Capture/Compare Register 1, High Byte Capture/Compare Register 2, Low Byte Capture/Compare Register 2, High Byte Capture/Compare Interrupt Request Flag Register Capture/Compare Interrupt Enable Register Compare output initialization register Trap Enable Register Compare Output in Trap State Register Address E1H DEH DFH E6H E7H E3H E4H F2H F3H F4H F5H F6H F7H E5H D6H E2H FFH F9H The following sections describe the CAPCOM registers in detail. User’s Manual 6-61 2001-05 C508 On-Chip Peripheral Components Writing the CAPCOM Period/Offset/Compare Registers on-the-Fly If Compare Timer 1 is running, then the period, offset or compare registers can be written with modified values for generating new periods or duty cycles of the compare output signals. For proper synchronization purposes, a special mechanism for updating of the 16-bit offset, period, and compare registers is implemented in the C508. This mechanism is based on shadow latches. When new values for offset, period, or compare registers have been written into the shadow latches, the real register update operation must be initiated by setting bit STE1 (shadow transfer enable) in SFR CT1CON. When this bit is set, the content of the shadow latches is transferred to the real registers when Compare Timer 1 has reached its period value or zero value. This applies to both operating modes 0 and 1. When the register transfer has been executed, STE1 is reset by hardware. So the software can recognize when the register transfer has occurred. When Compare Timer 1 is started by setting the run bit CT1R the first time after reset, a shadow register transfer into the real registers is automatically executed. In this case STE1 must not be set. Care must be taken when programming a new compare value. If the new compare value is greater than or equal to the period value, the reload should be delayed till the next zero match (Compare Timer 1 reaches 0000H) instead of the approaching period match (Compare Timer 1 reaches period value). This can be achieved by setting bit STE1 only in the period match interrupt service routine. If the desired compare value is less than the offset value, the COUT bits in COINI register must be inverted first, before the reload is allowed. User’s Manual 6-62 2001-05 C508 On-Chip Peripheral Components Compare Timer 1 Control Register The 16-bit Compare Timer 1 is controlled by the bits of the CT1CON register. With this register the count mode, the trap interrupt enable, the compare timer start/stop and reset, and the timer input clock rate is controlled. Special Function Register CT1CON (Address E1H) Bit No. MSB 7 E1H CTM Reset Value: 00010000B LSB 0 CLK0 CT1CON 6 ETRP 5 4 3 2 CLK2 1 CLK1 STE1 CT1RES CT1R Bit CTM Function Compare Timer 1 operating mode selection CTM = 0 selects operating mode 0 (up count) and CTM = 1 selects operating mode 1 (up/down count) for Compare Timer 1. CCU emergency trap interrupt enable If ETRP = 1, the emergency interrupt for the CCU trap signal is enabled. CAPCOM unit shadow latch transfer enable When STE1 is set, the content of the Compare Timer 1 period, Compare and offset registers (CCPH, CCPL, CCHx, CCLx, CT1OFH, CT1OFL) is transferred to its real registers when Compare Timer 1 reaches the next time the period value or value 0000H. After the shadow transfer event, STE1 is reset by hardware. Compare Timer 1 input clock selection The input clock for the Compare Timer 1 is derived from the clock rate fOSC of the C508 via a programmable prescaler. The following table shows the programmable prescaler ratios. CLK2 0 0 0 0 1 1 1 1 CLK1 0 0 1 1 0 0 1 1 CLK0 0 1 0 1 0 1 0 1 Function Compare timer 1 input clock is Compare timer 1 input clock is Compare timer 1 input clock is Compare timer 1 input clock is Compare timer 1 input clock is Compare timer 1 input clock is Compare timer 1 input clock is Compare timer 1 input clock is 2 fOSC ETRP STE1 CLK2 CLK1 CLK0 fOSC fOSC/2 fOSC/4 fOSC/8 fOSC/16 fOSC/32 fOSC/64 User’s Manual 6-63 2001-05 C508 On-Chip Peripheral Components Bit Function CT1RES Compare timer 1 reset control CT1R Compare timer 1 run/stop control These two bits control the start, stop, and reset function of Compare Timer 1. CT1RES is used to reset Compare Timer 1 and CT1R is used to start and stop the Compare Timer 1. The following table shows the functions of these two bits: CT1RES 0 1 CT1R 0 0 Function Compare Timer 1 is stopped and holds its value; the compare outputs stay in the logic state as they are. Compare Timer 1 is stopped and reset; compare outputs are set to the logic state as defined in SFR COINI (default after reset). Compare Timer 1 starts. Before CT1R is set the first time, the CMSEL register should be programmed (enable Capture/Compare functions). Compare Timer 1 starts running from count value 0000H; compare outputs are set to the logic state as defined in SFR COINI. Compare Timer 1 is stopped and holds its value; the Compare outputs drive their actual logic state. Compare Timer 1 is stopped and reset to 0000H; Compare outputs are set to the logic state as defined in SFR COINI. 0 0→1 1 0→1 0 1 1→0 1→0 Note for Capture mode: Setting CT1R = 0 and CT1RES = 1 after a capture event will destroy the value stored in the capture register CCx. Therefore, CT1RES should be set to 0 in capture mode. Reason: if CT1R = 0 and CT1RES = 1 all shadow registers are transparent (switched directly) to the real registers. Note: When software power-down mode is entered with CT1RES bit of SFR CT1CON set, the Compare Timer 1 is reset after the execution of a wake-up from powerdown mode procedure. When CT1RES is cleared before software power-down mode is entered and a wake-up from power-down mode procedure has been executed, the Compare Timer 1 is not reset. Depending on the state of bit CT1R at power-down mode entry, the Compare Timer 1 either stops (CT1R = 0) or continues (CT1R = 1) counting after a wake-up from power-down mode procedure. Further details of the power-down mode are provided in Chapter 9.2. User’s Manual 6-64 2001-05 C508 On-Chip Peripheral Components Compare Timer 1 Period Registers The Compare Timer 1 period registers CCPH and CCPL store the 16-bit value for the Compare Timer 1 count period. CCPH holds the high byte of the 16-bit period value and CCPL holds the low byte. If CCPH/CCPL is written, shadow latches are always loaded. The contents of these shadow latches are transferred to the real registers when STE1 is set and the Compare Timer 1 reaches its period value (operating mode 0) or count value 0000H (operating mode 1). When the Compare Timer 1 period registers are read, shadow latches are always accessed. Special Function Register CCPL (Address DEH) Special Function Register CCPH (Address DFH) Bit No. MSB 7 DEH .7 Reset Value: 00H Reset Value: 00H LSB 0 LSB CCPL 6 .6 5 .5 4 .4 3 .3 2 .2 1 .1 DFH MSB .6 .5 .4 .3 .2 .1 .0 CCPH Bit CCPL.7 - 0 Function Compare Timer 1 period value, low byte The 8-bit value in the CCPL register is the low byte of the 16-bit period value of Compare Timer 1 (shadow latch). Compare Timer 1 period value, high byte The 8-bit value in the CCPH register is the high byte of the 16-bit period value of Compare Timer 1 (shadow latch). CCPH.7 - 0 User’s Manual 6-65 2001-05 C508 On-Chip Peripheral Components Compare Timer 1 Offset Registers The CT1OFH and CT1OFL registers contain the value for the Compare Timer 1. CT1OFH holds the high byte of the 16-bit offset value and CT1OFL holds the low byte. For the detection of a compare match event, which results in changing polarity of a COUTx compare output signal, the content of CT1OFH/CT1OFL is always added to the actual value of the Compare Timer 1. The value stored in the offset registers has no effect on the signal generation at the CCx compare outputs. If the Compare Timer 1 offset registers are written, shadow latches are always loaded. The content of these shadow latches is transferred to the real registers when STE1 is set and the Compare Timer 1 reaches its period value or count value 0000H. When the Compare Timer 1 offset registers are read, shadow latches are always accessed. Special Function Register CT1OFL (Address E6H) Special Function Register CT1OFH (Address E7H) Bit No. MSB 7 E6H .7 Reset Value: 00H Reset Value: 00H LSB 0 LSB CT1OFL 6 .6 5 .5 4 .4 3 .3 2 .2 1 .1 E7H MSB .6 .5 .4 .3 .2 .1 .0 CT1OFH Bit CT1OFL.7 - 0 Function 8-bit Compare Timer 1 offset value, low byte The 8-bit value in the CT1OFL register is the low byte of the offset value for Compare Timer 1 (shadow latch). 8-bit Compare Timer 1 offset value, high byte The 8-bit value in the CT1OFH register is the high byte of the offset value for Compare Timer 1 (shadow latch). CT1OFH.7 - 0 To generate correct dead times for PWM signals, the offset value stored in CT1OFH/ CT1OFL must be lower than the values stored in the compare registers. User’s Manual 6-66 2001-05 C508 On-Chip Peripheral Components Capture/Compare Channel Mode Select Registers The capture/compare channels of the CAPCOM unit can operate individually either in compare mode or in capture mode. The CMSEL0 and CMSEL1 registers contain the mode select bits for the CAPCOM unit. Special Function Register CMSEL0 (Address E3H) Special Function Register CMSEL1 (Address E4H) Bit No. MSB 7 E3H 6 5 4 3 2 1 Reset Value: 00H Reset Value: 00H LSB 0 CMSEL0 CMSEL CMSEL CMSEL CMSEL CMSEL CMSEL CMSEL CMSEL 13 12 11 02 01 00 10 03 CAPCOM Channel 1 7 E4H 6 5 0 4 0 3 ESMC NMCS CAPCOM Channel 0 2 1 0 CMSEL1 CMSEL CMSEL CMSEL CMSEL 23 22 21 20 CAPCOM Channel 2 Bit ESMC Function Enable software controlled multi-channel PWM modes If ESMC = 0, switching of the follower state in 4-/5-/6-phase multi-channel PWM mode is controlled by Compare Timer 1 reaching its period value. If ESMC = 1, switching of the follower state in 4-/5-/6-phase multi-channel PWM mode is controlled by bit NMCS. Next multi-channel PWM state Setting bit NMCS (with ESMC set) will select the follower state in the 4/5/6-phase multi-channel PWM mode, which is taken into account at the output pins, when Compare Timer 1 is 0. Bit NMCS is reset by hardware in the next clock cycle after it has been set. Switching Compare Timer 2 output signal to COUTx If CMSELx3 is set and compare mode is selected for the outputs COUTx, the output signal of the 10-bit Compare unit, typically a higher frequency signal, is switched (modulated) to the COUTx pin. The state of the corresponding COINI bit at the start of Compare Timer 1 defines the logic level of the CAPCOM channel output signal at which the COMP output signal is output to COUTx. COINI is set: The COMP output is switched to COUTx during the low phase of the CAPCOM channel X signal. COINI is cleared: The COMP output is switched to COUTx during the high phase of the CAPCOM channel X signal. NMCS CMSELx3 x = 0-2 User’s Manual 6-67 2001-05 C508 On-Chip Peripheral Components Bit CMSELx2- 0 x = 0-2 Function CAPCOM Capture/Compare mode enable bits The CMSEL registers are used to select/enable the operating mode and the output/input pin configuration of the capture/compare channels. Each CAPCOM channel can be programmed individually for either compare or capture operation. CMSEL x2 0 CMSEL x1 0 CMSEL x0 0 Mode Compare outputs disabled; No compare output signal is generated; CCx and COUTx are normal I/O pins. Compare output on pin CCx enabled; COUTx is normal I/O pin. Compare output on pin COUTx enabled; CCx is normal I/O pin. Compare outputs on pins CCx and COUTx enabled. Capture mode enabled; signal transitions at CCx do not generate a capture event. COUTx is a normal I/O pin or analog input pin. Capture mode enabled; CCx is configured as a Capture input and a rising edge at CCx transfers compare timer 1 content into the capture register. COUTx is a normal I/O pin or analog input pin. Capture mode enabled; CCx is configured as a Capture input and a falling edge at CCx transfers compare timer 1 content into the capture register. COUTx is a normal I/O pin or analog input pin. Capture mode enabled; CCx is configured as a capture input. Rising and falling edge at CCx transfer the compare timer 1 content into the capture register. COUTx is a normal I/O pin or analog input pin. 0 0 0 1 0 1 1 0 1 0 1 0 1 0 1 1 1 0 1 1 1 Note: Only CC0/COUT0 can be analog inputs if not selected as compare output. In compare mode, the two output signals of a CAPCOM channel can be enabled selectively. In capture mode, the type of signal transition which will generate a capture event can be chosen. User’s Manual 6-68 2001-05 C508 On-Chip Peripheral Components Capture/Compare Registers of CAPCOM Unit The capture/compare registers are 16-bit registers, organized as two 8-bit byte-wide registers. Each of the three CAPCOM channels has one capture/compare register. In compare mode, they hold a compare value which typically defines the duty cycle of the output signals. In capture mode, the actual Compare Timer 1 value is transferred into the Capture/Compare registers at a Capture event. If CCLx/CCHx is written, shadow latches are always loaded. The content of these shadow latches is transferred to the real registers when STE1 is set and the Compare Timer 1 reaches its period value (operating mode 0) or count value 0000H (operating mode 1). When the Capture/Compare registers are read, the real registers are always accessed because of capture mode. Special Function Registers CCL0/CCH0 (Addresses F2H / F3H) Special Function Registers CCL1/CCH1 (Addresses F4H / F5H) Special Function Registers CCL2/CCH2 (Addresses F6H / F7H) Bit No. MSB 7 F2H F3H .7 MSB 6 .6 .6 5 .5 .5 4 .4 .4 3 .3 .3 2 .2 .2 1 .1 .1 Reset Value: 00H Reset Value: 00H Reset Value: 00H LSB 0 LSB .0 CCL0 CCH0 F4H F5H .7 MSB .6 .6 .5 .5 .4 .4 .3 .3 .2 .2 .1 .1 LSB .0 CCL1 CCH1 F6H F7H .7 MSB .6 .6 .5 .5 .4 .4 .3 .3 .2 .2 .1 .1 LSB .0 CCL2 CCH2 Bit CCLx.7 - 0 x = 0-2 CCHx.7 - 0 x = 0-2 Function Capture/Compare value, low byte The 8-bit value in the CCLx register is the low byte of the 16-bit capture/compare value of channel x. Capture/Compare value, high byte The 8-bit value in the CCHx register is the low byte of the 16-bit capture/compare value of channel x. 6-69 2001-05 User’s Manual C508 On-Chip Peripheral Components Capture/Compare Interrupt Request Flags/Register The interrupt flags of the CAPCOM capture/compare match and Compare Timer 1 interrupt are located in the register CCIR. All CAPCOM capture/compare match interrupt flags are set by hardware and must be cleared by software. A capture/compare match interrupt is generated by setting of a CCxR bit (x = 0-2) if the corresponding enable bits are set. The Compare Timer 1 interrupt is triggered by the CT1FP or CT1FC bits of SFR CCIR. Special Function Register CCIR (Address E5H) Bit No. MSB 7 E5H 6 5 4 CC2R 3 CC1F 2 CC1R 1 CC0F Reset Value: 00H LSB 0 CC0R CCIR CT1FP CT1FC CC2F CAPCOM Channel 2 CAPCOM Channel 1 CAPCOM Channel 0 Bit CT1FP Function Compare Timer 1 period flag Compare Timer 1 operating mode 0: CT1FP is set if Compare Timer 1 reaches the period value. Compare Timer 1 operating mode 1: CT1FP is set if Compare Timer 1 reaches the period value and changes the count direction from up- to down counting Bit CT1FP must be cleared by software. If Compare Timer 1 interrupt is enabled, the setting of CT1FP will generate a Compare Timer 1 interrupt. Compare Timer 1 count direction change flag This flag can only be set if Compare Timer 1 runs in operating mode 1 (CTM = 1). CT1FC is set when Compare Timer 1 reaches count value 0000H and changes the count direction from down- to up-counting. If Compare Timer 1 interrupt is enabled, the setting of CT1FC will generate a Compare Timer 1 interrupt. Bit CT1FC must be cleared by software. CT1FC User’s Manual 6-70 2001-05 C508 On-Chip Peripheral Components Bit CCxR x = 0-2 Function Capture/Compare match on up-count flag Capture Mode: CCxR is set at a low-to-high transition (rising edge) of the corresponding CCx Capture input signal. Compare Mode: CCxR is set if the Compare timer 1 value matches the Compare register CCx value during the up-count phase. Capture/Compare match on down-count flag Capture Mode: CCxF is set at a high-to-low transition (falling edge) of the corresponding CCx capture input signal. Compare Mode: CCxF is set if the Compare Timer 1 value matches the compare register CCx value during the down-count phase (only in Compare Timer 1 operating mode 1). CCxF x = 0-2 User’s Manual 6-71 2001-05 C508 On-Chip Peripheral Components Capture/Compare Interrupt Enable Register The bits of the interrupt enable register CCIE control the specific interrupt enable/disable functions of the CAPCOM part of the Capture/Compare unit. The bits ECTP and ECTC control the Compare Timer 1 period/count change interrupt. Depending on the mode in which Compare Timer 1 is running, interrupts can be generated at a period match or a count direction change event. The lower 6 bits of CCIE are the CAPCOM channel specific interrupt enable/disable control bits for the capture or compare match interrupt. The functions of these bits depend on the selected mode (capture or compare) of a capture/compare channel. In compare mode, compare channel specific interrupts can be generated at a match event between compare register content and compare timer 1 count value during the up- or down-counting phase of Compare Timer 1. In capture mode, capture channel specific interrupts can be generated selectively at rising or falling or both edges of the capture input signals at CCx. Special Function Registers CCIE (Address D6H) Bit No. MSB 7 D6H ECTP 6 ECTC 5 4 3 2 1 Reset Value: 00H LSB 0 CCIE CC2FEN CC2REN CC1FEN CC1REN CC0FEN CC0REN Bit ECTP Function Enable Compare Timer 1 period interrupt If ECTP = 0, the Compare Timer 1 period interrupt is disabled. Compare Timer 1 operating mode 0: If ECTP = 1, an interrupt is generated when Compare Timer 1 reaches the period value. Compare timer 1 operating mode 1: If ECTP = 1, an interrupt is generated when Compare Timer 1 reaches the period value and changes the count direction from up- to down-counting. User’s Manual 6-72 2001-05 C508 On-Chip Peripheral Components Bit ECTC Function Enable Compare Timer 1 count direction change interrupt status If ECTC = 0, the Compare Timer 1 count change interrupt is disabled. Compare timer 1 operating mode 0: Bit has no effect on the interrupt generation. Compare timer 1 operating mode 1: If ECTC = 1, an interrupt is generated when Compare Timer 1 reaches count value 0000H and changes its count direction from down- to up-counting. Capture/Compare rising edge interrupt enable Capture Mode: If CCxREN is set, an interrupt is generated at a low-to-high transition (rising edge) of the corresponding CCx input signal. Compare Mode: If CCxREN is set, an interrupt is generated if the Compare Timer 1 value matches the compare register CCx value during the up-counting phase of the Compare Timer 1. This function is available in both Compare Timer 1 operating modes. Capture/Compare falling edge interrupt enable Capture Mode: If CCxFEN is set, an interrupt is generated at a high-to-low transition (falling edge) of the corresponding CCx input signal. Compare Mode: If CCxFEN is set, an interrupt is generated only in Compare timer mode 1 if the Compare Timer 1 value matches the Compare register CCx value during the down-counting phase of the Compare Timer 1. This function is available only in Compare Timer 1 operating mode 1. CCxREN (x = 0-2) CCxFEN (x = 0-2) User’s Manual 6-73 2001-05 C508 On-Chip Peripheral Components Compare Output Initialization Register COINI The six lower bits of the COINI register define the initial values (passive levels) of the Port 1 lines, which are programmed to be used as a compare output. If an output of the CAPCOM unit is enabled for compare mode operation by writing the corresponding bit combination into the CMSEL0/CMSEL1 registers, the compare output is switched into push-pull mode and starts driving an initial logic level as defined by the bits of the COINI register. Bit COUTXI controls an inverter for the COMP unit output signal, when it is wired to the CCx and COUTx outputs in burst or multi-channel PWM mode. COUT3I defines the initial logic level at COUT3 before Compare Timer 2 is started as well as the logic state when COUT3 is disabled by setting bit ECT2O in SFR CT2CON (see Figure 6-32). The COINI register should be written prior to the starting of the compare timers. Any write operation to the COINI register when the compare timer is running will affect the compare output signals immediately and drive the logic value as defined by the bits of COINI. A PWM output signal of the C508 basically consists of two phases, an inactive phase and an active phase. The inactive phase of a PWM output signal is defined by the bit in the register COINI. A ‘1’ in bit location 0 to 5 of COINI defines the high level of the corresponding PWM compare output signal as its inactive phase. With a ‘0’, a low level is selected as the inactive phase. User’s Manual 6-74 2001-05 C508 On-Chip Peripheral Components Special Function Register COINI (Address E2H) Bit No. MSB 7 E2H 6 5 4 CC2I Reset Value: FFH 2 CC1I 3 COUT1I 1 COUT0I LSB 0 CC0I COUT3I COUTXI COUT2I COINI CAPCOM Channel 2 CAPCOM Channel 1 CAPCOM Channel 0 Bit COUT3I Function COUT3 initial logic level This bit defines the initial logic state of the output COUT3 before Compare Timer 2 is started the first time. Further, COUT3I defines the logic state of output COUT3 when bit ECT2O (CT2CON.6) is reset (COUT3 disabled). Compare Timer 1 output signal inversion in burst and block commutation When COUTXI is set, the output signal of Compare Timer 2 which is wired to the compare outputs COUTx (x = 0-2) in burst or block commutation mode is inverted. Compare output initial value Bits at even bit positions (0, 2, 4) are assigned to the CCx compare outputs. Bits at odd bit positions (1, 3, 5) are assigned to the COUTx compare outputs. CCxI, COUTxI = 0: If Compare Timer 1 is not running (after reset), an output CCx/COUTx (x = 0-2) is switched into push-pull mode and starts driving an initial value of 0 when this CCx/COUTx output is programmed as compare output by writing the corresponding bit combination into the CMSEL0/CMSEL1 registers. CCxI, COUTxI = 1: If Compare Timer 1 is not running (after reset), an output CCx/COUTx (x = 0-2) is switched into push-pull mode and starts driving an initial value of 1 when this CCx/COUTx output is programmed as compare output by writing the corresponding bit combination into the CMSEL0/CMSEL1 registers. The COINI values are valid only for capture/compare outputs enabled for compare mode operation. COUTXI CCxI, COUTxI (x = 0-2) User’s Manual 6-75 2001-05 C508 On-Chip Peripheral Components Trap Enable Register The trap enable register TREN is used to enable selectively the compare outputs of the three CAPCOM channels for switching it into high or low level in the trap state as defined by the bits of the COTRAP register. Additionally, for a general enable of the trap function, bit TRPEN must be set. The TRF flag indicates when a low level is detected at the CTRAP input signal. Special Function Register TRCON (Address FFH) Bit No. MSB 7 FFH TRPEN 6 TRF 5 4 3 2 1 Reset Value: 00H LSB 0 TREN5 TREN4 TREN3 TREN2 TREN1 TREN0 TRCON CAPCOM Channel 2 CAPCOM Channel 1 CAPCOM Channel 0 Bit TRPEN Function External CTRAP trap function enable bit This bit is a general enable bit for the trap function of the CTRAP input signal. TRPEN = 0: External trap input CTRAP is disabled (default after reset). TRPEN = 1: External trap input CTRAP is enabled; Trap flag TRF is set by hardware if the trap function is enabled (TRPEN = 1) and the CTRAP level becomes active (low). If enabled, an interrupt is generated when TRF is set. TRF must be reset by software. Trap enable control bits Bits at even bit positions (0, 2, 4) are assigned to the CCx Compare outputs. Bits at odd bit positions (1, 3, 5) are assigned to the COUTx Compare outputs. TRENx = 0: Compare channel output provides CAPCOM output signal in trap state. TRENx = 1: Compare channel output is enabled to set the logic level of the compare output CCx or COUTx in the trap state to a logic state as defined by the corresponding bits of the COTRAP register. When writing TREN0-5, bit TRF should be reset to 0. Otherwise, setting TREN0-5 will generate a software trap interrupt. TRF TREN5-0 User’s Manual 6-76 2001-05 C508 On-Chip Peripheral Components Compare Output in Trap State Register The six lower bits of the COTRAP register define the values of Port 1 pins 2 to 7, which are programmed to be used as compare outputs, when a trap state is entered. Bit 6 is reserved and must always be written with a ‘0’. Bit 7 selects either one of the two block commutation tables for rotate left that is provided. Special Function Register COTRAP (Address F9H) Bit No. MSB 7 F9H BCTSEL Reset Value: 00H 1 LSB 0 COTRAP 6 RES 5 4 3 2 COUT2T CC2T COUT1T CC1T COUT0T CC0T CAPCOM Channel 2 CAPCOM Channel 1 CAPCOM Channel 0 Bit BCTSEL Function Block Commutation Table (Rotate Left) Select BCTSEL = 0: The table for 60° phase angle will be selected. BCTSEL = 1: The table for 0° phase angle will be selected. Reserved This bit must always be written with a ‘0’. Writing a ‘1’ to this bit is prohibited. Compare output level in trap condition Bits at even positions (0, 2, 4) are assigned to the CCx compare outputs. Bits at odd positions (1, 3, 5) are assigned to the COUTx compare outputs. CCxT, COUTxT = 0: If the compare timer is running, the compare channel output CCx, COUTx (x = 0-2) will be switched to 0 level in trap state if the channel is enabled for trap function. CCxT, COUTxT = 1: If the compare timer is running, the compare channel output CCx, COUTx (x = 0-2) will be switched to 1 level in trap state if the channel is enabled for trap function. RES CCxT, COUTxT (x = 0-2) User’s Manual 6-77 2001-05 C508 On-Chip Peripheral Components 6.3.3 Compare (COMP) Unit Operation The Capture/Compare Unit of the C508 also provides a 10-bit Compare Unit (COMP) which operates as a single channel pulse generator with a pulse width modulated output signal. This output signal is available at the output pin COUT3 of the C508. In the combined multi-channel PWM modes and in burst mode of the CAPCOM unit the output signal of the COMP unit can also be switched to the output signals COUTx or CCx. Figure 6-32 shows the block diagram and the pulse generation scheme of the COMP unit (for example: the initial value of COUT3 is set to 0). To CAPCOM Output Control Compare Registers CMP2H/CMP2L COUTXI (COINI.6) Port Pin COUT3 2fOSC Programmable Prescaler Comparator Match Pulse Generation Period Registers CP2H/CP2L Compare Timer 2 10-Bit Up Counter COUT3I (COINI.7) Control Register CT2CON ECT20 CT2 Value Reset of CT2 CP2H/CP2L CMP2H/CMP2L Start of CT2 COUT3 (COUT3I = 0) COUT3 (COUT3I = 1) 0 0 0 Time MCB04069 Figure 6-32 COMP Unit: Block Diagram and Pulse Generation Scheme User’s Manual 6-78 2001-05 C508 On-Chip Peripheral Components The COMP unit has a 10-bit up-counter (Compare Timer 2, CT2) which starts counting from 000H up to the value stored in the period register and then is again reset. This Compare Timer 2 operation is similar to the operating mode 0 of Compare Timer 1. When the count value of CT2 matches the value stored in the compare registers CMP2H/CMP2L, COUT3 toggles its logic state. When Compare Timer 2 is reset to 000H, COUT3 toggles again its logic state. COUT3 is only an output pin. After a reset operation COUT3 drives a high level as defined by the reset value (= 1) of bit COUT3I of SFR COINI. When Compare Timer 2 is running (bit CT2R in SFR CT2CON is set), bit ECT2O in SFR CT2CON allows the disconnection of COUT3 from Compare Timer 2 signal generation. In this case, the logic value of COUT3I (bit COINI.7) is put to the COUT3 output. When ECT2O is set thereafter, the Compare Timer 2 output signal is again switched to the COUT3 output. In the combined multi-channel PWM modes and in the burst mode, the Compare Timer 2 output signal can also be switched to the CAPCOM output pins COUT0, COUT1, and COUT3. In these modes, the polarity of the modulated output signal at COUT2-0 can be inverted by setting bit COUTXI (COINI.6) 6.3.3.1 COMP Registers The COMP unit has five SFRs which are listed in Table 6-8. Table 6-8 Unit COMP Compare Unit Special Function Registers of the COMP Unit Symbol CT2CON CP2L CP2H CMP2L CMP2H Description Compare Timer 2 control register Compare Timer 2 period register, low byte Compare Timer 2 period register, high byte Compare Timer 2 Compare register, low byte Compare Timer 2 Compare register, high byte Address F1H D2H D3H D4H D5H The Compare Timer 2 period and compare registers store a 10-bit value, organized in two bytes. For proper synchronization purposes, these registers are not written directly. Each value of a write operation to these registers is stored in shadow latches. The transfer of these shadow latches into the real registers is synchronized with the Compare Timer 2 value 000H and controlled by bit STE2. When the period or compare value is changed by writing the corresponding SFR, the setting of bit STE2 (CT2CON.5) enables the write transfer of the shadow registers into the real registers. This shadow latch transfer happens when the Compare Timer 2 reaches the count value 000H the next time after STE2 has been set. With the automatic transfer of the shadow latches to the real registers, bit STE2 is reset by hardware. When the Compare Timer 2 period and compare registers are initialized after reset, bit STE2 must also be set to enable the shadow latch transfer when Compare Timer 2 is started the first time. Note: Read operations with the Compare Timer 2 period and compare registers always access the shadow registers and not the real registers. User’s Manual 6-79 2001-05 C508 On-Chip Peripheral Components Compare Timer 2 Control Register The 10-bit Compare Timer 2 is controlled by the bits of the CT2CON register. With this register the count mode, the timer input clock rate, and the compare timer reset function is controlled. Special Function Register CT2CON (Address F1H) Bit No. MSB 7 F1H Reset Value: 00010000B LSB 0 CLK0 CT2CON 6 5 4 3 2 CLK2 1 CLK1 CT2P ECT2O STE2 CT2RES CT2R Bit CT2P Function Compare Timer 2 period flag When the Compare Timer 2 value matches with the Compare Timer 2 period register value, bit CT2P is set. If the Compare Timer 2 interrupt is enabled, the setting of CT2P will generate a Compare Timer 2 interrupt. Bit CT2P must be cleared by software. Enable Compare timer 2 output When ECT2O is cleared and Compare Timer 2 is running, output COUT3 is put into the logic state as defined by bit COUT3I which is located in SFR COINI.6. When ECT2O is set and Compare Timer 2 is running, the Compare Timer 2 output COUT3 is enabled and outputs the PWM signal of the COMP unit. COMP unit shadow latch transfer enable When STE2 is set, the content of the Compare Timer 2 period and compare latches (CP2H, CP2L, CMP2H, CMP2L) is transferred to its real registers when Compare Timer 2 reaches the period value. After the shadow transfer event, STE2 is reset by hardware. ECT2O STE2 User’s Manual 6-80 2001-05 C508 On-Chip Peripheral Components Bit CT2RES CT2R Function Compare Timer 2 reset control Compare Timer 2 run/stop control These two bits controls the start, stop, and reset function of the Compare Timer 2. CT2RES is used to reset Compare Timer 2; and CT2R is used to start or stop Compare Timer 2. The following table shows the functions of these two bits: CT2RES CT2R Function 0 0 0 1 Compare Timer 2 is stopped; compare output COUT3 stays in the logic state as it is. Compare Timer 2 is running. If CT2R is set the first time after reset, COUT3 is set to the logic state as defined by bit COUT3I of SFR COINI. Compare Timer 2 is stopped and reset. The output COUT3 is set to the logic state as defined by bit COUT3I of SFR COINI (default after reset). Compare Timer 2 is further running. 1 0 1 1 ECT2O must be set for COUT3 signal output enable. CLK2 CLK1 CLK0 Compare Timer 2 input clock selection The input clock for the Compare Timer 2 is derived from the clock rate fOSC of the C508 via a programmable prescaler. The following table shows the programmable prescaler ratios. CLK2 0 0 0 0 1 1 1 1 CLK1 0 0 1 1 0 0 1 1 CLK0 0 1 0 1 0 1 0 1 Function Compare Timer 2 input clock is 2 fOSC Compare Timer 2 input clock is fOSC Compare Timer 2 input clock is fOSC/2 Compare Timer 2 input clock is fOSC/4 Compare Timer 2 input clock is fOSC/8 Compare Timer 2 input clock is fOSC/16 Compare Timer 2 input clock is fOSC/32 Compare Timer 2 input clock is fOSC/64 Note: With a reset operation (external or internal) Compare Timer 2 is reset (000H) and stopped. When software power-down mode is entered with CT2RES bit of SFR CT2CON set, the Compare Timer 2 is reset after the execution of a wake-up from User’s Manual 6-81 2001-05 C508 On-Chip Peripheral Components power-down mode procedure. When CT2RES is cleared before software power down mode is entered and a wake-up from power-down mode procedure has been executed, the Compare Timer 2 is not reset. Depending on the state of bit CT2R at power down mode entry, the Compare Timer 2 either stops (CT2R = 0) or continues (CT2R = 1) counting after a wake-up from power-down mode procedure. Further details of the power-down mode are described in Chapter 9.2. Compare Timer 2 Period Registers The Compare Timer 2 period registers CP2L/CP2H hold the 10-bit value for the Compare Timer 2 period. When the Compare Timer 2 value is equal to the value stored in the period register, the COUT3 signal changes from inactive to active state. If CP2H/ CP2L is written, only shadow latches are written. The content of these latches is transferred to the real registers at compare timer count value 000H, using bit STE2 of SFR CT2CON. When the Compare Timer 2 period registers CP2L/CP2H are read, the shadow registers are always accessed. Special Function Register CP2L (Address D2H) Special Function Register CP2H (Address D3H) Bit No. MSB 7 D2H D3H .7 – 6 .6 – 5 .5 – 4 .4 – 3 .3 – 2 .2 – Reset Value: 00H Reset Value: XXXXXX00B 1 .1 .1 LSB 0 .0 .0 CP2L CP2H Bit CP2L.7 - 0 Function Compare Timer 2 period value, low byte The CP2L register holds the lower 8 bits of the 10-bit period value for Compare Timer 2 (shadow latch). Compare Timer 2 period value, high bits The CP2H register holds most significant two bits of the 10-bit period value for Compare Timer 2 (shadow latch). Reserved bits CP2H.1 - 0 – User’s Manual 6-82 2001-05 C508 On-Chip Peripheral Components Compare Timer 2 Compare Registers The compare registers CMP2H/CMP2L of Compare Timer 2 hold the 10-bit compare value which defines the duty cycle of the output signal at COUT3. When the Compare Timer 2 value is equal to the value stored in the CMP2H/CMP2L register, the COUT3 signal changes from passive to active state. If CMP2H/CMP2L is written, only shadow latches are written. The content of these latches is transferred to the real registers when compare timer count value 000H is reached and bit STE2 of SFR CT2CON has been set. When the compare registers CMP2H/CMP2L are read, the shadow registers are always accessed. Special Function Registers CMP2L (Address D4H) Special Function Registers CMP2H (Address D5H) Bit No. MSB 7 D4H D5H .7 – Reset Value: 00H Reset Value: XXXXXX00B LSB 0 .0 .0 CMP2L CMP2H 6 .6 – 5 .5 – 4 .4 – 3 .3 – 2 .2 – 1 .1 .1 Bit CMP2L.7 - 0 Function Compare Timer 2 compare value, low byte The CMP2L register holds the lower 8 bits of the 10-bit compare value for Compare Timer 2. Compare Timer 2 compare value, high bits The CMP2H register holds most significant two bits of the 10-bit Compare value for Compare Timer 2. Reserved bits CMP2H.1 - 0 – User’s Manual 6-83 2001-05 C508 On-Chip Peripheral Components 6.3.4 Combined Multi-Channel PWM Modes The CCU of the C508 has been designed to support also motor control or inverter applications which have a demand for specific multi-channel PWM signal generation. In these combined multi-channel PWM modes the CAPCOM unit (Compare Timer 1) and the COMP unit (Compare Timer 2) of the C508 CCU are working together. In the combined multi-channel PWM modes the signal generation of the CCx and COUTx PWM outputs can basically be controlled either by the interrupt inputs INT0 to INT2 (block commutation mode) or by the operation of Compare Timer 1 or by software (multi-channel PWM mode). In the active phase of a combined multi-channel PWM mode, Compare Timer 1 compare output signal or the Compare Timer 2 output signal or both can be switched selectively to the CCx or COUTx PWM output lines. The combined multi-channel PWM modes are controlled by the BCON (block commutation control) register. Figure 6-33 shows the block diagram of the multi-channel PWM mode logic which is integrated in the C508. CCU Emergency Interrupt Combined Multi-Channel PWM Control (BCON) PWM Capture Interrupt Period/ Comp. Match Interrupt Channel 0 in Capture Mode 16-Bit Compare Timer 1 10-Bit Compare Timer 2 Trap Control CTRAP INT0 INT1 INT2 Port 1 Control Logic CC0 CC1 CC2 COUT0 COUT1 COUT2 COUT3 MCB02608 Figure 6-33 Block Diagram of the Combined Multi-Channel PWM Modes User’s Manual 6-84 2001-05 C508 On-Chip Peripheral Components In block commutation mode, a well defined incoming digital signal pattern of e.g. hall sensor signals, which are applied to the INT0-2 inputs, is sampled. Each transition at the INT0-2 inputs results in a change of the state of the PWM outputs. In block commutation mode, all six PWM output signals CCx and COUTx (x = 0-2) are outputs. According to a block commutation table (Table 6-10), the outputs CCx are put either to a low or high state while the outputs COUTx are switched to the PWM signal which is generated by the 10-bit Compare Timer 2 (COMP unit). For monitoring of sensor input signal timing in block commutation mode, the signal transitions at INT0-2 can also generate an interrupt (if enabled) and a capture event at channel 0 of the CAPCOM unit (Compare Timer 1). For emergency cases, (trap function of CTRAP input signal) the six outputs CCx and COUTx can be put selectively to the levels as defined by the first six bits in COTRAP register. At the multi-channel PWM modes of the C508, a change of the PWM output states (active or inactive) is triggered by Compare Timer 1, which is running either in operating mode 0 or 1. If its count value reaches 0000H, the PWM output signal changes its state according to a well defined state table. The multi-channel PWM modes consists of three modes: – 4-phase multi-channel PWM mode (4 PWM output signals) – 5-phase multi-channel PWM mode (5 PWM output signals) – 6-phase multi-channel PWM mode (6 PWM output signals) User’s Manual 6-85 2001-05 C508 On-Chip Peripheral Components 6.3.4.1 Control Register BCON The BCON register controls the selection of multi-channel PWM modes. It also contains the block commutation interrupt enable and status bit/flag. Special Function Register BCON (Address D7H) Reset Value: 00H Bit No. MSB LSB 7 6 5 4 3 2 1 0 BCMP PWM1 PWM0 EBCE BCERR BCEN BCM1 BCM0 D7H BCEM BCON Bit BCMP Function In multi-channel PWM mode: Machine polarity If BCMP is set and multi-channel PWM mode is selected (PWM1, 0 ≠ 0, 0), all enabled compare outputs COUTx and CCx are switched to the Compare Timer 2 output signal during their active phase. If BCMP is cleared, only the COUTx outputs are switched to the Compare Timer 2 output signal during the active phase in multi-channel PWM mode. CMSELx3 must be set for that functionality. In block commutation mode: Error mode select bit If BCEM is set in block commutation mode, in rotate right or rotate left mode additionally a “wrong follower” condition causes the setting of BCERR if EBCE is set. Multi-channel PWM mode selection These bits select the operating mode of the multi-channel PWM modes. PWM1 0 0 1 1 PWM0 Function 0 1 0 1 Block commutation mode (for hall sensor inputs) 4-phase multi-channel PWM mode 5-phase multi-channel PWM mode 6-phase multi-channel PWM mode BCEM PWM1 PWM0 EBCE Enable interrupt of block commutation mode error If EBCE is set, the emergency interrupt for a block commutation mode error condition of the CCU is enabled. In block commutation mode, an emergency error condition occurs if a false signal state at INT2 - INT0 or a wrong follower state (if selected by bit BCEM) is detected (see also Table 6-10). User’s Manual 6-86 2001-05 C508 On-Chip Peripheral Components Bit BCERR Function Block commutation mode error flag In block commutation mode BCERR is set in rotate right or rotate left mode if after a transition at INTx all INTx inputs are at high or low level. Additionally, in rotate right or rotate left mode a “wrong follower” condition according to Table 6-10 can cause the setting of BCERR (see description of bit BCEM). If the block commutation interrupt is enabled (EBCE = 1), the setting of BCERR will generate a CCU emergency interrupt. BCERR must be reset by software. Block commutation enable If BCEN is set, the multi-channel PWM modes of the CAPCOM unit as selected by the bits PWM1/PWM0 are enabled for operation. Before BCEN bit is set, all required PWM Compare outputs should be programmed to operate as compare outputs by writing the registers CMSEL1/CMSEL0. Multi-channel PWM mode output pattern selection Additionally to bits PWM1 and PWM0, these two control bits select the output signal pattern in all multi-channel PWM modes. The detailed signal pattern information is given in Table 6-10 to Table 6-13. BCM1 0 0 1 1 BCM0 0 1 0 1 Function Idle mode Rotate right mode Rotate left mode Slow down mode BCEN BCM1 BCM0 Note: When a multi-channel PWM mode is initiated the first time after reset, BCON must be written twice: first write operation with bit BCEN cleared and all other bits set/ cleared as required (BCM1, 0 must be 0, 0 for idle mode), followed by a second write operation with the same BCON bit pattern of the first write operation but with BCEN set. After this second BCON write operation, Compare Timer 1 can be started (setting CT1R in CT1CON) and thereafter BCM1, 0 can be put into another mode than idle mode. User’s Manual 6-87 2001-05 C508 On-Chip Peripheral Components 6.3.4.2 Signal Generation in Multi-Channel PWM Modes The multi-channel PWM modes of the C508 use the pins CCx and COUTx for compare output signal generation. Before signal generation of a multi-channel PWM mode can be started, the COINI register should be programmed with the logic value of the multichannel PWM inactive phase. After this, the output pins which are required for the multichannel PWM signal generation must be programmed to operate as compare outputs by writing the mode select registers CMSEL0 and CMSEL1. Table 6-9 shows the CMSEL0/ CMSEL1 register bits which are required for the full operation of the multi-channel PWM modes. Table 6-9 Programming of Multi-Channel PWM Compare Outputs CMSEL1 XXXX Y011B CMSEL0 Y011 Y011B Y010 Y011B Y010 Y001B Multi-Channel PWM Mode Block commutation / 6-phase multi-channel PWM 5-phase multi-channel PWM 4-phase multi-channel PWM Note: The abbreviation “X” means don’t care. The abbreviation “Y” (bit CMSELx.3) represents the burst mode bit. If Y = 0 the signal generation at the COUTx pins is controlled by Compare Timer 1. If Y = 1 the signal generation at the COUTx pins is also controlled by Compare Timer 1 but modulated by Compare Timer 2. Output Signals During the Active Phase An active phase of a compare output signal in multi-channel PWM mode can be controlled either by the CAPCOM unit (Compare Timer 1) and/or modulated by Compare Timer 2. The selection is done by bit CMSELx.3 (see note below Table 6-9). Figure 6-34 shows the different possibilities for controlling the active phase of a compare output signal using Compare Timer 1. Compare Timer 1 may operate either in mode 0 or mode 1. In multi-phase mode, the block commutation logic switches from one state to the next state when Compare Timer 1 reaches the value 0000H. As an active phase always lasts for two states, the duration of an active phase is determined by Compare Timer 1 reaching 0000H twice. As shown in Figure 6-34a, a compare output signal CCx or COUTx of a CAPCOM channel is either at low or high level during the whole active phase when the value stored in the Compare Timer 1 offset registers (CT1OFH, CT1OFL) and the value stored in its compare registers (CCHx, CCLx) is equal 0000H. When the compare value is not equal 0000H and less or equal the period value, the active phase of the related compare output signal CCx or COUTx is controlled by the CAPCOM unit as shown in Figure 6-34b. User’s Manual 6-88 2001-05 C508 On-Chip Peripheral Components a) No transitions in active phase (offset and compare value = 0) COINI Bit = 1 Compare Timer 1 Mode 0 CCx COUTx Compare Timer 1 Mode 1 CCx COUTx Compare Timer 1 Mode 0 CCx COUTx Compare Timer 1 Mode 1 CCx COUTx COINI Bit = 0 _ b) CAPCOM transitions in active phase (0 < compare value < period value; offset value = 0) COINI Bit = 1 Compare Timer 1 Mode 0 CCx COUTx Compare Timer 1 Mode 1 CCx COUTx : Active Phase Compare Timer1 Mode 0 CCx COUTx Compare Timer 1 Mode 1 CCx COUTx COINI Bit = 0 MCT02609 Figure 6-34 Compare Timer 1 Controlled Active Phase of the Multi-Channel PWM Modes (with CMSELx.3 = 0) User’s Manual 6-89 2001-05 C508 On-Chip Peripheral Components Figure 6-35 shows the different possibilities for controlling the active phase of a compare output signal using Compare Timer 2. In this operating mode, which is selected when bit CMSELx.3 is set, the Compare Timer 2 output signal is switched to the COUTx or CCx outputs during the active phase of a multi-channel PWM signal. Bit BCMP (BCON.7) defines whether only COUTx or COUTx and CCx are modulated by the Compare Timer 2 output signal. Depending on the bits COUT3I and COUTXI of COINI, the polarity of COUT3 and the switched CCx/COUTx active phase signal can be identical or inverted. Bit CMSELx.3 = 1: Compare timer 2 transitions in active phase at COUTx COINI Bit = 1 Compare Timer 1 Mode 0 Compare Timer 2 Output Signal CCx COUTx CCx COUTx Active Phase MCD04071 COINI Bit = 0 Compare Timer 1 Mode 0 Compare Timer 2 Output Signal COUTxI = 1 CCx COUTx CCx COUTx COUTxI = 0 COUTxI = 0 COUTxI = 1 Figure 6-35 Compare Timer 2 Controlled Active Phase of the Multi-Channel PWM Modes (with CMSELx.3 = 1) User’s Manual 6-90 2001-05 C508 On-Chip Peripheral Components 6.3.4.3 Block Commutation PWM Mode In block commutation mode the INT0-2 inputs are sampled once each processor cycle. If the input signal combination at INT0-2 changes its state, the outputs CCx and COUTx are set to their new state according to Table 6-10. Table 6-10 Mode (BCM1, BCM0) Block Commutation Control Table INT0 - INT2 Inputs INT0 INT1 INT2 CC0 0 1 0 0 1 1 1 0 0 0 1 1 1 0 1 0 0 0 1 1 X X 0 1 1 0 0 0 1 1 1 0 0 0 1 1 0 0 1 1 1 0 X X CC0 - CC2 Outputs CC1 CC2 COUT0 - COUT2 Outputs COUT0 COUT1 COUT2 0 Rotate left1) 1) Rotate right 1 Rotate left, 60° phase shift (BCTSEL = 0, default) 1 1 1 0 0 0 1 Rotate left, 0° phase shift 1 (BCTSEL - 1) 1 0 0 0 Rotate right 1 1 1 0 0 0 Slow down Idle 1) inactive inactive inactive inactive inactive inactive inactive inactive inactive inactive inactive inactive inactive inactive active inactive active inactive active active active active inactive inactive inactive inactive inactive active inactive inactive inactive active inactive inactive inactive inactive inactive inactive inactive active inactive inactive inactive active inactive active inactive active active inactive inactive active inactive inactive active inactive inactive active inactive active inactive active active active active active inactive inactive inactive inactive inactive active inactive inactive inactive active inactive inactive inactive inactive inactive inactive active inactive inactive inactive active inactive inactive inactive active inactive inactive inactive inactive active inactive inactive inactive active inactive active active inactive inactive inactive inactive inactive active active inactive active inactive active inactive inactive active inactive inactive active inactive active X X inactive inactive inactive active 2) inactive inactive inactive inactive inactive inactive If one of these two combinations of INTx signals is detected in rotate left or rotate right mode, bit BCERR flag is set. If enabled, a CCU emergency interrupt can be generated. When these states (error states) are reached, idle state is entered immediately. User’s Manual 6-91 2001-05 C508 On-Chip Peripheral Components 2) Idle state is also entered when a “wrong follower” is detected (if bit BCON.7 = BCEM is set). When idle state is entered, the BCERR flag is always set. Idle state can only be left when the BCERR flag is reset by software. Two tables are available for “rotate left” direction. The first table is identical to the one in C504 which has a 60° phase shift. It is selected if bit BCTSEL of SFR COTRAP is cleared. The second table has 0° phase shift, and it is selected if bit BCTSEL is set. After reset, the first table is selected by default. This option is provided as a feature so that a wider range of motors can be operated at optimum performance. In block commutation mode, any signal transition at INT0-2 generates a capture pulse for CAPCOM channel 0 (CCH0/CCL0), independently from the selected INT0-2 signal transition type as defined in the SFR TCON (for INT0 and INT1) and SFR T2CON (for INT2). User’s Manual 6-92 2001-05 C508 On-Chip Peripheral Components Figure 6-36 gives an example of a block commutation mode timing (only COUTx outputs are modulated with Compare Timer 2 output signal). It shows the case for rotate left at 60° phase shift (BCM1, BCM0 = 1, 0; BCTSEL = 0) and the rotate right case (BCM1, BCM0 = 0, 1). For the timing shown in Figure 6-36 the COINI register is set to XX111111B. This means that a high level is defined as inactive phase. The CMSELx.3 bits in the CMSEL0/CMSEL1 registers must also be set (Compare Timer 2 switched to COUTx during active phase). The timing shown below is directly derived from Table 6-10. a) Block commutation mode timing in rotate left mode (BCM1, 0 = 1, 0) INT0 INT1 INT2 CC0 CC1 CC2 COUT0 COUT1 COUT2 Output Signals 1 0 1 1 0 0 1 1 0 0 1 0 0 1 1 0 0 1 Input Signals b) Block commutation mode timing in rotate right mode (BCM1, 0 = 0, 1) INT0 INT1 INT2 CC0 CC1 CC2 COUT0 COUT1 COUT2 MCT02611 1 1 0 1 0 0 1 0 1 0 0 1 0 1 1 0 1 0 Input Signals Output Signals Figure 6-36 Block Commutation Mode Timing User’s Manual 6-93 2001-05 C508 On-Chip Peripheral Components 6.3.4.4 Compare Timer 1 Controlled Multi-Channel PWM Modes Using the multi-channel PWM modes of the C508, several Compare Timer 1 controlled PWM waveforms can be generated: – 4-phase multi-channel PWM waveforms – 5-phase multi-channel PWM waveforms – 6-phase multi-channel PWM waveforms The basic waveforms of these three Compare Timer 1 controlled PWM modes are shown in the following three figures, Figure 6-37 to Figure 6-39. The figures show waveforms for different COINI values with the resulting active/inactive phases and rotate right / rotate left condition. All three figures assume that Compare Timer 1 operates with 100% duty cycle (compare and offset registers = 0000H) and without Compare Timer 2 modulation. Compare Timer 1 duty cycles less than 100% or Compare timer 2 modulation in the multi-channel PWM modes are shown in Figure 6-34 and Figure 6-35. a) Timing in rotate left mode (BCM1, 0 = 1, 0) with COINI XX111111 B Start Compare Timer 1 CC0 COUT1 CC2 COUT2 State No. 1 2 3 4 1 2 3 4 1 2 Low = Active Phase b) Timing in rotate right mode (BCM1, 0 = 0, 1) with COINI XX000000 B Start Compare Timer 1 CC0 COUT1 CC2 COUT2 State No. 2 1 4 3 2 1 4 3 2 1 MCT02612 High = Active Phase Figure 6-37 Basic Compare Timer 1 Controlled 4-Phase PWM Timing User’s Manual 6-94 2001-05 C508 On-Chip Peripheral Components a) Timing in rotate left mode (BCM1, 0 = 1, 0) with COINI XX111111 B Start Compare Timer 1 CC0 COUT1 CC2 COUT0 COUT2 State No. 1 2 3 4 5 1 2 3 4 5 1 Low = Active Phase b) Timing in rotate right mode (BCM1, 0 = 0, 1) with COINI XX000000 B Start Compare Timer 1 CC0 COUT1 CC2 COUT0 COUT2 State No. 2 1 5 4 3 2 1 5 4 3 2 MCT02614 High = Active Phase Figure 6-38 Basic Compare Timer 1 Controlled 5-Phase PWM Timing User’s Manual 6-95 2001-05 C508 On-Chip Peripheral Components a) Timing in rotate left mode (BCM1, 0 = 1, 0) with COINI XX111111 B Start Compare Timer 1 CC0 COUT1 CC2 COUT0 CC1 COUT2 State No. 1 2 3 4 5 6 1 2 3 4 5 Low = Active Phase b) Timing in rotate right mode (BCM1, 0 = 0, 1) with COINI XX000000 B Start Compare Timer 1 CC0 COUT1 CC2 COUT0 CC1 COUT2 State No. 2 1 6 5 4 3 2 1 6 5 4 MCT02615 High = Active Phase Figure 6-39 Basic Compare Timer 1 Controlled 6-Phase PWM Timing User’s Manual 6-96 2001-05 C508 On-Chip Peripheral Components Table 6-11 to Table 6-13 show the basic signal pattern definitions of the three multichannel PWM modes. They also include information about slow down mode and idle mode (bits BMC1, 0 = 0, 0 and 1, 1). Table 6-11 No. CC0 0 1 2 3 4 5 inactive active active inactive inactive inactive 4-Phase PWM Timing State Table Follower State (No.) BCM1, BCM0 = COUT2 inactive active inactive inactive active active 0, 1 2 4 1 2 3 2 1, 0 1 2 3 4 1 1 0, 0 0 0 0 0 0 0 1, 1 5 5 5 5 5 5 Output Signals COUT1 inactive inactive active active inactive active CC2 inactive inactive inactive active active inactive Actual State and PWM Phase Note: In the inactive phase the PWM outputs drive a logic state as defined by the related bits in register COINI. During the active phase, the PWM outputs can be modulated by CT1 and/or CT2. Table 6-12 No. CC0 0 1 2 3 4 5 6 inactive active active inactive inactive inactive inactive 5-Phase PWM Timing State Table Actual State and PWM Phase Output Signals COUT1 inactive inactive active active inactive inactive active CC2 inactive inactive inactive active active inactive inactive COUT0 inactive inactive inactive inactive active active active COUT2 inactive active inactive inactive inactive active active 0, 1 2 5 1 2 3 4 2 Follower State (No.) BCM1, BCM0 = 1, 0 1 2 3 4 5 1 1 0, 0 0 0 0 0 0 0 0 1, 1 6 6 6 6 6 6 6 Note: In the inactive phase, the PWM outputs drive a logic state as defined by the related bits in register COINI. During the active phase, the PWM outputs can be modulated by CT1 and/or CT2. User’s Manual 6-97 2001-05 C508 On-Chip Peripheral Components Table 6-13 No. CC0 0 1 2 3 4 5 6 7 active 6-Phase PWM Timing State Table Actual State and PWM Phase Output Signals COUT1 CC2 active COUT0 CC1 inactive inactive inactive inactive inactive inactive 2 inactive inactive inactive inactive 5 active inactive inactive inactive 1 active inactive inactive 2 active inactive 3 active 4 5 2 inactive active Follower State (No.) BCM1, BCM0 = COUT2 0, 1 1, 0 0, 0 1, 1 1 2 3 4 5 6 1 1 0 0 0 0 0 0 0 0 7 7 7 7 7 7 7 7 inactive inactive active inactive inactive inactive active active inactive inactive inactive inactive active inactive active inactive active inactive inactive inactive inactive active inactive active Note: In the inactive phase, the PWM outputs drive a logic state as defined by the related bits in register COINI. During the active phase, the PWM outputs can be modulated by CT1 and/or CT2. User’s Manual 6-98 2001-05 C508 On-Chip Peripheral Components 6.3.4.5 Software Controlled State Switching in Multi-Channel PWM Modes In the 4-/5-/6-phase multi-channel PWM modes, the Compare Timer 1 overflow controlled switching of the follower state can be switched off. Instead of the Compare Timer 1 overflow, a setting of bit NMCS in SFR CMSEL1 selects the follower state, which is defined in the Table 6-11 to Table 6-13. Bit ESMC in SFR CMSEL1 enables the software controlled state switching. If this software controlled 4-/5-/6-phase multi-channel PWM mode generation is selected, the Compare Timer 1 can be used for PWM signal generation (compare mode) in order to modulate the outputs. It can be further used, for example, for timer based interrupt generation. The waveforms of a PWM output signal in the multi-channel PWM modes can be selected as shown in Figure 6-34 (static low or high during active phase) or as shown in Figure 6-35 (Compare Timer 2 controlled modulation during active phase). Figure 6-40 shows for the 5-pole PWM timing the possible waveforms of the active phase when the software controlled state switching in the multi-channel PWM modes is selected. User’s Manual 6-99 2001-05 C508 On-Chip Peripheral Components 5-Phase Multi-Channel PWM Mode: Rotate Left Mode (BCM1, 0 = 1, 0) with COINI XX111111 B Bit NMCS CC0 COUT1 CC2 COUT0 COUT2 State No. 1 2 3 4 5 1 2 3 4 5 1 1 0 Setting bit NMCS by software Static level during active phase (at CCx and COUTx outputs) Active Phase Compare timer 2 modulation during active phase (at CCx and COUTx output!) MCD04073 Figure 6-40 Software Controlled State Switching in 5-Phase Multi-Channel PWM Mode Static Level during Active Phase: When bit ESMC in SFR CMSEL1 is set, static active or passive output levels during the active phase of a multi-phase PWM timing are generated when the following conditions are met: – The 16-bit offset register of Compare Timer 1 must be 0000H (CT1OFH = CT1OFL = 00H) – static active: compare values = 0000H static passive: compare values > period value – The bits CMSELx3 (x = 0-2) in the SFRs CMSEL0/CMSEL1 must be 0. The logic state of the inactive/active phases at the CCx and COUTx outputs is defined by the bits in SFR COINI. User’s Manual 6-100 2001-05 C508 On-Chip Peripheral Components Compare Timer 2 Controlled Active Phase at COUTx: When bit ESMC in SFR CMSEL1 is set, Compare Timer 2 controlled output levels at COUTx during the active phase of a multi-pole PWM timing are generated when the following conditions are met: – The 16-bit offset register of Compare Timer 1 must be 0000H (CT1OFH = CT1OFL = 00H) – The 16-bit capture/compare registers must be 0000H (CCL0 = CCH0 = CCL1 = CCH1 = CCL2 = CCH2 = 00H) – Bits CMSELx3 (x = 0-2) in the SFRs CMSEL0/CMSEL1 must be set – Compare Timer 2 must be enabled and initialized for compare output signal generation Both, the CCx and the COUTx outputs can be controlled by Compare Timer 2. A combination of outputs modulated by Compare Timer 1 and/or Compare Timer 2 is supported. 6.3.4.6 Trap Function in Multi-Channel Block Commutation Mode The trap function in block commutation mode is similar to the trap function described in Chapter 6.3.2.7, “Trap Function of the CAPCOM Unit in Compare Mode”. But there is one difference: when CTRAP becomes inactive (high), the CCx and COUTx outputs are again switched back to the PWM pulse generation when Compare Timer 2 reaches the count value 000H (instead of Compare Timer 1 in all other modes). All other trap functions of the multi-channel PWM modes are identical as described in Chapter 6.3.2.7. User’s Manual 6-101 2001-05 C508 On-Chip Peripheral Components 6.4 Serial Interface The serial port is a full duplex port capable of simultaneous transmit and receive functions. It is also receive-buffered; it can commence reception of a second byte before a previously-received byte has been read from the receive register. (However, if the first byte still has not been read before reception of the second byte is complete, one of the bytes will be lost). The serial port receive and transmit registers are both accessed at special function register SBUF. Writing to SBUF loads the transmit register, and reading SBUF accesses a physically separate receive register. The serial port can operate in 4 modes (one synchronous mode, three asynchronous modes). The baudrate clock for the serial port is derived from the oscillator frequency (Modes 0 and 2) or generated either by Timer 1 or a dedicated baudrate generator (Modes 1 and 3). Mode 0, Shift Register (Synchronous) Mode: Serial data enters and exits through RxD. TxD outputs the shift clock. Eight data bits are transmitted/received with the Least Significant Bit (LSB) first. The baudrate is fixed at 1/ 3 of the oscillator frequency (see Chapter 6.4.4 for more detailed information). Mode 1, 8-Bit USART, Variable Baudrate: Ten bits are transmitted through TxD or received through RxD: a start bit (0), 8 data bits (LSB first), and a stop bit (1). On receive, the stop bit goes into RB8 in special function register SCON. The baudrate in Mode 1 is variable (see Chapter 6.4.5 for more detailed information). Mode 2, 9-Bit USART, Fixed Baudrate: Eleven bits are transmitted through TxD or received through RxD: a start bit (0), 8 data bits (LSB first), a programmable 9th bit, and a stop bit (1). On transmit, the 9th data bit (TB8 in SCON) can be assigned to the value of ‘0’ or ‘1’. Alternatively, the parity bit (P, in the PSW) could be moved into TB8 an example. On receive, the 9th data bit goes into RB8 in special function register SCON, while the stop bit is ignored. The baudrate is programmable to either 1/8 or 1/16 of the oscillator frequency (see Chapter 6.4.6 for more detailed information). Mode 3, 9-Bit USART, Variable Baudrate: Eleven bits are transmitted (through TxD) or received (through RxD): a start bit (0), 8 data bits (LSB first), a programmable 9th data bit, and a stop bit (1). In fact, Mode 3 is the same as Mode 2 in all respects except the baudrate. The baudrate in Mode 3 is variable (see Chapter 6.4.6 for more detailed information). User’s Manual 6-102 2001-05 C508 On-Chip Peripheral Components In all four modes, transmission is initiated by any instruction that uses SBUF as a destination register. Reception is initiated in Mode 0 by the condition RI = 0 and REN = 1. Reception is initiated in the other modes by the incoming start bit if REN = 1. The serial interface also provides interrupt requests when transmission or reception of a frame is completed. The corresponding interrupt request flags are TI or RI, respectively. See Chapter 7 for more details about the interrupt structure. The interrupt request flags, TI and RI, can also be used for polling the serial interface, if the serial interrupt is not to be used (that is, serial interrupt is not enabled). 6.4.1 Multiprocessor Communication Modes 2 and 3 have a special provision for multiprocessor communications. In these modes, 9 data bits are received. The 9th bit goes into RB8. Then comes a stop bit. The port can be programmed such that when the stop bit is received, the serial port interrupt will be activated only if RB8 = 1. This feature is enabled by setting bit SM2 in SCON. One use of this feature in multiprocessor systems is described here. When the master processor wants to transmit a block of data to one of several slaves, it first sends out an address byte which identifies the target slave. An address byte differs from a data byte in that the 9th bit is ‘1’ in an address byte and ‘0’ in a data byte. With SM2 = 1, no slave will be interrupted by a data byte. An address byte, however, will interrupt all slaves, so that each slave can examine the received byte and see if it is being addressed. The addressed slave will clear its SM2 bit and prepare to receive the data bytes that will be coming. The slaves which were not being addressed keep their SM2s set and ignore the incoming data bytes. SM2 has no effect in Mode 0. In Mode 1, it can be used to check the validity of the stop bit. In a Mode 1 reception, if SM2 = 1, the receive interrupt will not be activated unless a valid stop bit is received. 6.4.2 Serial Port Registers The serial port control and status register is the special function register SCON. This register contains not only the mode selection bits, but also the 9th data bit for transmit and receive (TB8 and RB8), and the serial port interrupt bits (TI and RI). SBUF is the receive and transmit buffer of serial interface. Writing to SBUF loads the transmit register and initiates transmission. Reading out SBUF accesses a physically separate receive register. User’s Manual 6-103 2001-05 C508 On-Chip Peripheral Components Special Function Register SCON (Address 98H) Special Function Register SBUF (Address 99H) Bit No. MSB 9FH 98H SM0 7 99H 9EH SM1 6 9DH SM2 5 9CH REN 4 9BH TB8 3 9AH RB8 2 99H TI 1 Reset Value: 00H Reset Value: XXH LSB 98H RI 0 SBUF SCON Serial Interface Buffer Register Bit SM0 SM1 Function Serial Port 0 operating mode selection bits SM0 0 0 1 1 SM1 0 1 0 1 Selected operating mode Serial mode 0: Shift register, fixed baudrate (fOSC/3) Serial mode 1: 8-bit USART, variable baudrate Serial mode 2: 9-bit USART, fixed baudrate (fOSC/8 or fOSC/16) Serial mode 3: 9-bit USART, variable baudrate SM2 Enable serial port multiprocessor communication in Modes 2 and 3 In Mode 2 or 3, if SM2 is set to 1, then RI will not be activated if the received 9th data bit (RB8) is 0. In Mode 1, if SM2 = 1 then RI will not be activated if a valid stop bit is not received. In Mode 0, SM2 should be 0. Enable receiver of serial port Set by software to enable serial reception. Cleared by software to disable serial reception. Serial port transmitter bit 9 TB8 is the 9th data bit that will be transmitted in Modes 2 and 3. Set or cleared by software as desired. Serial port receiver bit 9 In Modes 2 and 3, RB8 is the 9th data bit that is received. In Mode 1, if SM2 = 0, RB8 is the stop bit that is received. In Mode 0, RB8 is not used. REN TB8 RB8 User’s Manual 6-104 2001-05 C508 On-Chip Peripheral Components Bit TI Function Serial port transmitter interrupt flag TI is set by hardware at the end of the 8th bit time in Mode 0, or at the beginning of the stop bit in the other modes, in any serial transmission. TI must be cleared by software. Serial port receiver interrupt flag RI is set by hardware at the end of the 8th bit time in Mode 0, or halfway through the stop bit time in the other modes, in any serial reception (exception see SM2). RI must be cleared by software. RI User’s Manual 6-105 2001-05 C508 On-Chip Peripheral Components 6.4.3 Baudrate Generation There are several possibilities to generate the baudrate clock for the serial port, depending on the mode in which it is operating. To clarify the terminology, something should be said about the difference between “baudrate clock” and “baudrate”. The serial interface requires a clock rate which is 16 times the baudrate for internal synchronization. Therefore, the baudrate generators must provide a “baudrate clock” to the serial interface which - there divided by 16 - results in the actual “baudrate”. However, all formulae given in the following section already include the factor and calculate the final baudrate. The baudrate of the serial port is controlled by two bits which are located in the special function registers as shown below. Special Function Register ADCON0 (Address D8H) Special Function Register PCON (Address 87H) Bit No. MSB DFH BD 7 87H SMOD Reset Value: 00X00000B Reset Value: 00H LSB D8H MX0 0 IDLE PCON ADCON0 DEH CLK 6 PDS DDH – 5 IDLS DCH BSY 4 SD DBH ADM 3 GF1 DAH MX2 2 GF0 D9H MX1 1 PDE D8H The shaded bits are not used for controlling the baudrate. Bit BD Function Baudrate generator enable When set, the baudrate of the serial interface is derived from the dedicated baudrate generator. When cleared (default after reset), baudrate is derived from the timer 1 overflow rate. Double baudrate When set, the baudrate of serial interface in Modes 1, 2, 3 is doubled. After reset this bit is cleared. Reserved bits for future use. Read by CPU returns undefined values. SMOD – Note: Bit CLK of SFR ADCON0 must be written with a ‘0’. User’s Manual 6-106 2001-05 C508 On-Chip Peripheral Components Figure 6-41 shows the configuration for the baudrate generation of the serial port. Timer 1 Overflow ADCON0.7 (BD) 0 1 2fOSC Baudrate Generator (SRELH SRELL) Mode 1 Mode 3 Mode 2 Mode 0 SCON.7/ SCON.6 (SM0/SM1) PCON.7 (SMOD) ÷2 0 1 Baudrate Clock ÷6 Only one mode can be selected Note: The switch configuration shows the reset state MCS04074 Figure 6-41 Baudrate Generation for the Serial Port Depending on the programmed operating mode different paths are selected for the baudrate clock generation. Figure 6-41 shows the dependencies of the serial port baudrate clock generation on the two control bits and from the mode which is selected in the special function register SCON. 6.4.3.1 Baudrate in Mode 0 The baudrate in Mode 0 is fixed to: Mode 0 baudrate = oscillator frequency 3 6.4.3.2 Baudrate in Mode 2 The baudrate in Mode 2 depends on the value of bit SMOD in special function register PCON. If SMOD = 0 (which is the value after reset), the baudrate is 1/16 of the oscillator frequency. If SMOD = 1, the baudrate is 1/8 of the oscillator frequency. 2 SMOD × oscillator frequency 16 Mode 2 baudrate = User’s Manual 6-107 2001-05 C508 On-Chip Peripheral Components 6.4.3.3 Baudrate in Mode 1 and 3 In these modes the baudrate is variable and can be generated alternatively by a baudrate generator or by Timer 1. 6.4.3.3.1 Using the Internal Baudrate Generator In Modes 1 and 3, the C508 can use an internal baudrate generator for the serial port. To enable this feature, bit BD (bit 7 of special function register ADCON0) must be set. Bit SMOD (PCON.7) controls a divide-by-2 circuit which affect the input and output clock signal of the baudrate generator. After reset the divide-by-2 circuit is active and the resulting overflow output clock will be divided by 2. The input clock of the baudrate generator is 2 × fOSC (output of PLL). Baudrate Generator SRELH .1 .0 SRELL PCON.7 (SMOD) 2fOSC Input Clock 10-Bit Timer Overflow ÷2 0 1 Baudrate Clock MCS04075 Figure 6-42 Serial Port Input Clock when using the Baudrate Generator The baudrate generator consists of a free running upward counting 10-bit timer. On overflow of this timer (next count step after counter value 3FFH) there is an automatic 10-bit reload from the registers SRELL and SRELH. The lower 8 bits of the timer are reloaded from SRELL, while the upper two bits are reloaded from bit 0 and 1 of register SRELH. The baudrate timer is reloaded by writing to SRELL. User’s Manual 6-108 2001-05 C508 On-Chip Peripheral Components Special Function Register SRELH (Address BAH) Special Function Register SRELL (Address AAH) Bit No. MSB 7 BAH – 6 – 5 – 4 – 3 – 2 – 1 MSB .9 Reset Value: XXXXXX11B Reset Value: D9H LSB 0 .8 SRELH AAH .7 .6 .5 .4 .3 .2 .1 LSB .0 SRELL The shaded bits are not used for reload operation. Bit SRELH.0-1 SRELL.0-7 – Function Baudrate generator reload high value Upper two bits of the baudrate timer reload value. Baudrate generator reload low value Lower 8 bits of the baudrate timer reload value. Reserved bits for future use. Read by CPU returns undefined values. After reset, SRELH and SRELL have a reload value of 3D9H. With this reload value, the baudrate generator has an overflow rate of (input clock)/39. With 10 MHz oscillator frequency, a reload value of 37EH is required to achieve the commonly used baudrates of 4800 baud (SMOD = 0) and 9600 baud (SMOD = 1) at a deviation of 0.16%. With the baudrate generator as clock source for the serial port in Modes 1 and 3, the baudrate can be determined as follows: 2SMOD × oscillator frequency 16 × (baudrate generator overflow rate) Mode 1, 3 baudrate = Baudrate generator overflow rate = 210 - SREL with SREL = SRELH.1 - 0, SRELL.7 - 0 User’s Manual 6-109 2001-05 C508 On-Chip Peripheral Components 6.4.3.3.2 Using Timer 1 to Generate Baudrates When Timer 1 is used as the baudrate generator in Modes 1 and 3, the baudrates are determined by the Timer 1 overflow rate and the value of SMOD as follows: 2SMOD Mode 1, 3 baudrate = × (Timer 1 overflow rate) 32 The Timer 1 interrupt should be disabled in this application. Timer 1, itself, can be configured for either “timer” or “counter” operation, and in any of its operating modes. In most typical applications, it is configured for “timer” operation in the auto-reload mode (high nibble of TMOD = 0010B). In this case the baudrate is given by the formula: Mode 1, 3 baudrate = 2SMOD × oscillator frequency 32 × 3 × (256 - (TH1)) Very low baudrates can be achieved with Timer 1 by leaving the Timer 1 interrupt enabled, and configuring the timer to run as 16-bit timer (high nibble of TMOD = 0001B), and using the Timer 1 interrupt for a 16-bit software reload. User’s Manual 6-110 2001-05 C508 On-Chip Peripheral Components 6.4.4 Details about Mode 0 Serial data enters and exits through RxD. TxD outputs the shift clock. Eight data bits are transmitted/received with the LSB first. The baudrate is fixed at fOSC/3. Figure 6-43 shows a simplified functional diagram of the serial port in Mode 0. The associated timing is illustrated in Figure 6-44. Transmission is initiated by any instruction that uses SBUF as a destination register. The “Write-to-SBUF” signal at S6P2 also loads a ‘1’ into the 9th position of the transmit shift register and tells the TX control block to commence a transmission. The internal timing is such that one full machine cycle will elapse between “Write-to-SBUF”, and activation of SEND. SEND enables the output of the shift register to the alternative output function line of P3.0, and also enables SHIFT CLOCK to the alternative output function line of P3.1. SHIFT CLOCK is low during S3, S4, and S5 of every machine cycle, and high during S6, S1 and S2. At S6P2 of every machine cycle in which SEND is active, the contents of the transmit shift register are shifted to the right one position. As data bits shift out to the right, ‘0’s come in from the left. When the Most Significant Bit (MSB) of the data byte is at the output position of the shift register, the ‘1’ that was initially loaded into the 9th position is just to the left of the MSB, and all positions to the left of that contain ‘0’s. This condition flags the TX control block to do one last shift and then deactivate SEND and set TI. Both of these actions occur at S1P1 of the 10th machine cycle after “Write-to-SBUF”. Reception is initiated by the condition REN = 1 and RI = 0. At S6P2 of the next machine cycle, the RX control unit writes the bits “1111 1110” to the receive shift register, and in the next clock phase activates RECEIVE. RECEIVE enables SHIFT CLOCK to the alternative output function line of P3.1. SHIFT CLOCK makes transitions at S3P1 and S6P1 of every machine cycle. At S6P2 of every machine cycle in which RECEIVE is active, the contents of the receive shift register are shifted to the left one position. The value that comes in from the right is the value that was sampled at the P3.0 pin at S5P2 of the same machine cycle. As data bit comes in from the right, ‘1’s shift out to the left. When the ‘0’ which was initially loaded into the rightmost position arrives at the leftmost position in the shift register, it flags the RX control block to do one last shift and load SBUF. At S1P1 of the 10th machine cycle after the write to SCON that cleared RI, RECEIVE is cleared and RI is set. User’s Manual 6-111 2001-05 C508 On-Chip Peripheral Components Internal Bus 1 Write to SBUF S D CLK Zero Detector Shift Q SBUF & RXD P3.0 Alt. Output Function Start Baud Rate S6 Clock TX Control TX Clock TI Shift Send _