AT89C51RD2

Features • 80C52 Compatible – 8051 Instruction Compatible – Six 8-bit I/O Ports (64 Pins or 68 Pins Versions) – Four 8-bit I/O Ports (44 Pins Version) – Three 16-bit Timer/Counters – 256 Bytes Scratch Pad RAM – 9 Interrupt Sources with 4 Priority Levels Integrated Power Monitor (POR/PFD) to Supervise Internal Power Supply ISP (In-System Programming) Using Standard VCC Power Supply 2048 Bytes Boot ROM Contains Low Level Flash Programming Routines and a Default Serial Loader High-speed Architecture – In Standard Mode: • 40 MHz (Vcc 2.7V to 5.5V, both Internal and external code execution) • 60 MHz (Vcc 4.5V to 5.5V and Internal Code execution only) – In X2 mode (6 Clocks/machine cycle) • 20 MHz (Vcc 2.7V to 5.5V, both Internal and external code execution) • 30 MHz (Vcc 4.5V to 5.5V and Internal Code execution only) 64K Bytes On-chip Flash Program/Data Memory – Byte and Page (128 Bytes) Erase and Write – 100k Write Cycles On-chip 1792 bytes Expanded RAM (XRAM) – Software Selectable Size (0, 256, 512, 768, 1024, 1792 Bytes) – 768 Bytes Selected at Reset for T89C51RD2 Compatibility On-chip 2048 Bytes EEPROM Block for Data Storage (AT89C51ED2 Only) 100K Write Cycles Dual Data Pointer Variable Length MOVX for Slow RAM/Peripherals Improved X2 Mode with Independent Selection for CPU and Each Peripheral Keyboard Interrupt Interface on Port 1 SPI Interface (Master/Slave Mode) 8-bit Clock Prescaler 16-bit Programmable Counter Array – High Speed Output – Compare/Capture – Pulse Width Modulator – Watchdog Timer Capabilities Asynchronous Port Reset Full-duplex Enhanced UART with Dedicated Internal Baud Rate Generator Low EMI (Inhibit ALE) Hardware Watchdog Timer (One-time Enabled with Reset-Out), Power-off Flag Power Control Modes: Idle Mode, Power-down Mode Single Range Power Supply: 2.7V to 5.5V Industrial Temperature Range (-40 to +85°C) Packages: PLCC44, VQFP44, PLCC68, VQFP64 • • • • 8-bit Flash Microcontroller AT89C51RD2 AT89C51ED2 • • • • • • • • • • • • • • • • • • • 1. Description AT89C51RD2/ED2 is high performance CMOS Flash version of the 80C51 CMOS single chip 8bit microcontroller. It contains a 64-Kbyte Flash memory block for code and for data. The 64-Kbytes Flash memory can be programmed either in parallel mode or in serial mode with the ISP capability or with software. The programming voltage is internally generated from the standard VCC pin. The AT89C51RD2/ED2 retains all of the features of the Atmel 80C52 with 256 bytes of internal RAM, a 9-source 4-level interrupt controller and three timer/counters. The AT89C51ED2 provides 2048 bytes of EEPROM for nonvolatile data storage. In addition, the AT89C51RD2/ED2 has a Programmable Counter Array, an XRAM of 1792 bytes, a Hardware Watchdog Timer, SPI interface, Keyboard, a more versatile serial channel that facilitates multiprocessor communication (EUART) and a speed improvement mechanism (X2 Mode). The fully static design of the AT89C51RD2/ED2 allows to reduce system power consumption by bringing the clock frequency down to any value, including DC, without loss of data. The AT89C51RD2/ED2 has 2 software-selectable modes of reduced activity and an 8-bit clock prescaler for further reduction in power consumption. In the Idle mode the CPU is frozen while the peripherals and the interrupt system are still operating. In the Power-down mode the RAM is saved and all other functions are inoperative. The added features of the AT89C51RD2/ED2 make it more powerful for applications that need pulse width modulation, high speed I/O and counting capabilities such as alarms, motor control, corded phones, and smart card readers. Table 1-1. Memory Size and I/O Pins Flash (Bytes) 64K 64K XRAM (Bytes) 1792 1792 Total RAM (Bytes) 2048 2048 I/O 34 50 Package PLCC44/VQFP44 PLCC68/VQFP64 2 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 2. Block Diagram Figure 2-1. Block Diagram T2EX PCA Keyboard (1) RxD VCC TxD VSS ECI (2) (2) (1) (1) (1) (1) XTALA1 XTALA2 EUART RAM 256x8 Flash 64K x 8 XRAM 1792 x 8 T2 PCA Timer2 Keyboard Watch -dog EEPROM* 2K x 8 (AT89C51ED2) C51 CORE IB-bus ALE/ PROG PSEN EA RD WR (2) (2) CPU Parallel I/O Ports & Timer 0 Timer 1 INT Ctrl External Bus Port 0 Port 1 Port 2 Port 3 Port4 Port 5 SPI BOOT Regulator 2K x 8 POR / PFD ROM (2) (2) RESET T0 T1 (2) (2) P1 P2 P0 P3 INT0 INT1 P4 P5 (1) (1)(1)(1) MISO MOSI SCK SS (1): Alternate function of Port 1 (2): Alternate function of Port 3 3 4235K–8051–05/08 3. SFR Mapping The Special Function Registers (SFRs) of the AT89C51RD2/ED2 fall into the following categories: • C51 core registers: ACC, B, DPH, DPL, PSW, SP • I/O port registers: P0, P1, P2, P3, PI2 • Timer registers: T2CON, T2MOD, TCON, TH0, TH1, TH2, TMOD, TL0, TL1, TL2, RCAP2L, RCAP2H • Serial I/O port registers: SADDR, SADEN, SBUF, SCON • PCA (Programmable Counter Array) registers: CCON, CCAPMx, CL, CH, CCAPxH, CCAPxL (x: 0 to 4) • Power and clock control registers: PCON • Hardware Watchdog Timer registers: WDTRST, WDTPRG • Interrupt system registers: IE0, IPL0, IPH0, IE1, IPL1, IPH1 • Keyboard Interface registers: KBE, KBF, KBLS • SPI registers: SPCON, SPSTR, SPDAT • BRG (Baud Rate Generator) registers: BRL, BDRCON • Clock Prescaler register: CKRL • Others: AUXR, AUXR1, CKCON0, CKCON1 Table 3-1. Mnemonic ACC B PSW SP DPL DPH C51 Core SFRs Add E0h F0h D0h 81h 82h 83h Name Accumulator B Register Program Status Word Stack Pointer Data Pointer Low Byte Data Pointer High Byte CY AC F0 RS1 RS0 OV F1 P 7 6 5 4 3 2 1 0 Table 3-2. Mnemonic PCON AUXR AUXR1 CKRL CKCKON0 CKCKON1 System Management SFRs Add 87h 8Eh A2h 97h 8Fh AFh Name Power Control Auxiliary Register 0 Auxiliary Register 1 Clock Reload Register Clock Control Register 0 Clock Control Register 1 7 SMOD1 DPU 6 SMOD0 WDTX2 5 M0 ENBOOT PCAX2 4 POF XRS2 SIX2 3 GF1 XRS1 GF3 T2X2 2 GF0 XRS0 0 T1X2 1 PD EXTRAM T0X2 0 IDL AO DPS X2 SPIX2 4 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 3-3. Mnemonic IEN0 IEN1 IPH0 IPL0 IPH1 IPL1 Interrupt SFRs Add A8h B1h B7h B8h B3h B2h Name Interrupt Enable Control 0 Interrupt Enable Control 1 Interrupt Priority Control High 0 Interrupt Priority Control Low 0 Interrupt Priority Control High 1 Interrupt Priority Control Low 1 7 EA 6 EC PPCH PPCL 5 ET2 PT2H PT2L 4 ES PHS PLS 3 ET1 PT1H PT1L 2 EX1 ESPI PX1H PX1L SPIH SPIL PT0H PT0L 1 ET0 0 EX0 KBD PX0H PX0L KBDH KBDL Table 3-4. Mnemonic P0 P1 P2 P3 P4 P5 P5 Port SFRs Add 80h 90h A0h B0h C0h E8h C7h Name 8-bit Port 0 8-bit Port 1 8-bit Port 2 8-bit Port 3 8-bit Port 4 8-bit Port 5 8-bit Port 5 (byte addressable) 7 6 5 4 3 2 1 0 Table 3-5. Mnemonic TCON TMOD TL0 TH0 TL1 TH1 WDTRST WDTPRG T2CON T2MOD RCAP2H Timer SFRs Add 88h 89h 8Ah 8Ch 8Bh 8Dh A6h A7h C8h C9h CBh Name Timer/Counter 0 and 1 Control Timer/Counter 0 and 1 Modes Timer/Counter 0 Low Byte Timer/Counter 0 High Byte Timer/Counter 1 Low Byte Timer/Counter 1 High Byte WatchDog Timer Reset WatchDog Timer Program Timer/Counter 2 control Timer/Counter 2 Mode Timer/Counter 2 Reload/Capture High Byte Timer/Counter 2 Reload/Capture Low Byte Timer/Counter 2 High Byte TF2 EXF2 RCLK TCLK EXEN2 WTO2 TR2 WTO1 C/T2# T2OE WTO0 CP/RL2# DCEN 7 TF1 GATE1 6 TR1 C/T1# 5 TF0 M11 4 TR0 M01 3 IE1 GATE0 2 IT1 C/T0# 1 IE0 M10 0 IT0 M00 RCAP2L TH2 CAh CDh 5 4235K–8051–05/08 Table 3-5. Mnemonic TL2 Timer SFRs Add CCh Name Timer/Counter 2 Low Byte 7 6 5 4 3 2 1 0 Table 3-6. Mnemo -nic CCON CMOD CL CH PCA SFRs 7 CF CIDL 6 CR WDTE 5 4 CCF4 3 CCF3 2 CCF2 CPS1 1 CCF1 CPS0 0 CCF0 ECF Add Name D8h D9h E9h F9h PCA Timer/Counter Control PCA Timer/Counter Mode PCA Timer/Counter Low Byte PCA Timer/Counter High Byte CCAPM0 DAh PCA Timer/Counter Mode 0 CCAPM1 DBh PCA Timer/Counter Mode 1 CCAPM2 DCh PCA Timer/Counter Mode 2 CCAPM3 DDh PCA Timer/Counter Mode 3 CCAPM4 DEh PCA Timer/Counter Mode 4 CCAP0H FAh CCAP1H FBh ECOM0 ECOM1 ECOM2 ECOM3 ECOM4 CAPP0 CAPP1 CAPP2 CAPP3 CAPP4 CAPN0 CAPN1 CAPN2 CAPN3 CAPN4 MAT0 MAT1 MAT2 MAT3 MAT4 TOG0 TOG1 TOG2 TOG3 TOG4 PWM0 PWM1 PWM2 PWM3 PWM4 ECCF0 ECCF1 ECCF2 ECCF3 ECCF4 PCA Compare Capture Module 0 H CCAP0H7 CCAP0H6 CCAP0H5 CCAP0H4 CCAP0H3 CCAP0H2 CCAP0H1 CCAP0H0 PCA Compare Capture Module 1 H CCAP1H7 CCAP1H6 CCAP1H5 CCAP1H4 CCAP1H3 CCAP1H2 CCAP1H1 CCAP1H0 CCAP2H FCh PCA Compare Capture Module 2 H CCAP2H7 CCAP2H6 CCAP2H5 CCAP2H4 CCAP2H3 CCAP2H2 CCAP2H1 CCAP2H0 CCAP3H FDh PCA Compare Capture Module 3 H CCAP3H7 CCAP3H6 CCAP3H5 CCAP3H4 CCAP3H3 CCAP3H2 CCAP3H1 CCAP3H0 CCAP4H FEh CCAP0L CCAP1L CCAP2L CCAP3L CCAP4L PCA Compare Capture Module 4 H CCAP4H7 CCAP4H6 CCAP4H5 CCAP4H4 CCAP4H3 CCAP4H2 CCAP4H1 CCAP4H0 CCAP0L6 CCAP1L6 CCAP2L6 CCAP3L6 CCAP4L6 CCAP0L5 CCAP0L4 CCAP1L5 CCAP1L4 CCAP2L5 CCAP2L4 CCAP3L5 CCAP3L4 CCAP4L5 CCAP4L4 CCAP0L3 CCAP0L2 CCAP1L3 CCAP1L2 CCAP2L3 CCAP2L2 CCAP3L3 CCAP3L2 CCAP4L3 CCAP4L2 CCAP0L1 CCAP1L1 CCAP2L1 CCAP3L1 CCAP4L1 CCAP0L0 CCAP1L0 CCAP2L0 CCAP3L0 CCAP4L0 EAh PCA Compare Capture Module 0 L CCAP0L7 EBh PCA Compare Capture Module 1 L CCAP1L7 ECh PCA Compare Capture Module 2 L CCAP2L7 EDh PCA Compare Capture Module 3 L CCAP3L7 EEh PCA Compare Capture Module 4 L CCAP4L7 Table 3-7. Mnemonic SCON SBUF SADEN SADDR BDRCON BRL Serial I/O Port SFRs Add 98h 99h B9h A9h 9Bh 9Ah Name Serial Control Serial Data Buffer Slave Address Mask Slave Address Baud Rate Control Baud Rate Reload BRR TBCK RBCK SPD SRC 7 FE/SM0 6 SM1 5 SM2 4 REN 3 TB8 2 RB8 1 TI 0 RI Table 3-8. Mnemonic SPCON SPSTA SPDAT SPI Controller SFRs Add C3h C4h C5h Name SPI Control SPI Status SPI Data 7 SPR2 SPIF SPD7 6 SPEN WCOL SPD6 5 SSDIS SSERR SPD5 4 MSTR MODF SPD4 SPD3 SPD2 SPD1 SPD0 3 CPOL 2 CPHA 1 SPR1 0 SPR0 6 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 3-9. Mnemonic KBLS KBE KBF Keyboard Interface SFRs Add 9Ch 9Dh 9Eh Name Keyboard Level Selector Keyboard Input Enable Keyboard Flag Register 7 KBLS7 KBE7 KBF7 6 KBLS6 KBE6 KBF6 5 KBLS5 KBE5 KBF5 4 KBLS4 KBE4 KBF4 3 KBLS3 KBE3 KBF3 2 KBLS2 KBE2 KBF2 1 KBLS1 KBE1 KBF1 0 KBLS0 KBE0 KBF0 Table 3-10. Mnemonic EECON EEPROM data Memory SFR (AT89C51ED2 only) Add D2h Name EEPROM Data Control 7 6 5 4 3 2 1 EEE 0 EEBUSY shows all SFRs with their address and their reset value. Table 3-11. Bit Addressable 0/8 F8h B 0000 0000 P5 bit addressable 1111 1111 E0h ACC 0000 0000 CCON 00X0 0000 PSW 0000 0000 T2CON 0000 0000 P4 1111 1111 IPL0 X000 000 P3 1111 1111 IEN0 0000 0000 SADEN 0000 0000 IEN1 XXXX X000 SADDR 0000 0000 IPL1 XXXX X000 IPH1 XXXX X000 IPH0 X000 0000 CKCON1 XXXX XXX0 CMOD 00XX X000 FCON XXXX 0000 T2MOD XXXX XX00 CCAPM0 X000 0000 EECON xxxx xx00 RCAP2L 0000 0000 RCAP2H 0000 0000 SPCON 0001 0100 TL2 0000 0000 SPSTA 0000 0000 TH2 0000 0000 SPDAT XXXX XXXX P5 byte Addressable 1111 1111 BFh CCAPM1 X000 0000 CCAPM2 X000 0000 CCAPM3 X000 0000 CCAPM4 X000 0000 CL 0000 0000 CCAP0L XXXX XXXX CCAP1L XXXX XXXX CCAP2L XXXX XXXX CCAP3L XXXX XXXX CCAP4L XXXX XXXX 1/9 CH 0000 0000 2/A CCAP0H XXXX XXXX 3/B CCAP1H XXXX XXXX Non Bit Addressable 4/C CCAP2H XXXX XXXX 5/D CCAP3H XXXX XXXX 6/E CCAP4H XXXX XXXX 7/F FFh SFR Mapping F0h F7h E8h EFh E7h D8h DFh D0h D7h C8h CFh C0h C7h B8h B0h B7h A8h AFh 7 4235K–8051–05/08 Table 3-11. A0h P2 SFR Mapping AUXR1 0XXX X0X0 SBUF XXXX XXXX BRL 0000 0000 BDRCON XXX0 0000 KBLS 0000 0000 KBE 0000 0000 WDTRST XXXX XXXX KBF 0000 0000 CKRL 1111 1111 TMOD 0000 0000 SP 0000 0111 1/9 TL0 0000 0000 DPL 0000 0000 2/A TL1 0000 0000 DPH 0000 0000 3/B 4/C 5/D 6/E TH0 0000 0000 TH1 0000 0000 AUXR 0X00 1000 CKCON0 0000 0000 PCON 00X1 0000 7/F WDTPRG XXXX X000 A7h 1111 1111 SCON 0000 0000 P1 1111 1111 TCON 0000 0000 P0 1111 1111 0/8 98h 9Fh 90h 97h 88h 8Fh 80h 87h reserved 8 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 4. Pin Configurations Figure 4-1. Pin Configurations P1.1/T2EX/SS P1.4/CEX1 P1.3/CEX0 6 5 4 3 2 1 44 43 42 41 40 P1.5/CEX2/MISO P1.6/CEX3/SCK P1.7/CEx4/MOSI RST P3.0/RxD NIC* P3.1/TxD P3.2/INT0 P3.3/INT1 P3.4/T0 P3.5/T1 7 8 9 10 11 12 13 14 15 16 17 39 38 37 36 P0.4/AD4 P0.5/AD5 P0.6/AD6 P0.7/AD7 EA NIC* ALE/PROG PSEN P2.7/A15 P2.6/A14 P2.5/A13 P0.2/AD2 P0.3/AD3 35 34 33 32 31 30 29 P0.2/AD2 P0.3/AD3 P0.0/AD0 P2.1/A9 VCC AT89C51RD2/ED2 PLCC44 18 19 20 21 22 23 24 25 26 27 28 P3.6/WR P2.2/A10 P0.0/AD0 P0.1/AD1 P1.2/ECI P1.0/T2 NIC* VCC P1.1/T2EX/SS P1.4/CEX1 P1.3/CEX0 44 43 42 41 40 39 38 37 36 35 34 P1.5/CEX2/MISO P1.6/CEX3/SCK P1.7/CEX4/MOSI RST P3.0/RxD 1 2 3 4 5 6 7 8 9 10 11 33 32 31 30 29 28 27 26 25 24 23 P0.4/AD4 P0.5/AD5 P0.6/AD6 P0.7/AD7 EA NIC* P3.1/TxD P3.2/INT0 P3.3/INT1 P3.4/T0 P3.5/T1 AT89C51RD2/ED2 VQFP44 1.4 P0.1/AD1 P1.2/ECI P1.0/T2 NIC* P2.3/A11 P2.4/A12 P3.7/RD XTAL2 NIC* P2.0/A8 XTAL1 VSS NIC* ALE/PROG PSEN P2.7/A15 P2.6/A14 P2.5/A13 12 13 14 15 16 17 18 19 20 21 22 P2.3/A11 P2.4/A12 XTAL1 P2.2/A10 NIC* P2.0/A8 P3.6/WR P3.7/RD P2.1/A9 XTAL2 VSS 9 4235K–8051–05/08 P0.4/AD4 P5.4 P5.3 P0.5/AD5 P0.6/AD6 NIC P0.7/AD7 9 8 7 6 5 4 3 2 1 68 67 66 65 64 63 62 61 P5.5 P0.3/AD3 P0.2/AD2 P5.6 P0.1/AD1 P0.0/AD0 P5.7 VCC NIC P1.0/T2 P4.0 P1.1/T2EX/SS P1.2/ECI P1.3/CEX0 P4.1 P1.4/CEX1 P4.2 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 NIC ALE EA NIC P2.7/A15 P2.6/A14 P5.2 P5.1 P2.5/A13 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 P5.0 P2.4/A12 P2.3/A11 P4.7 P2.2/A10 P2.1/A9 P2.0/A8 P4.6 NIC VSS P4.5 XTAL1 XTAL2 P3.7/RD P4.4 P3.6/WR P4.3 NIC: Not Internaly Connected AT89C51ED2 PLCC68 P0.4/AD4 P5.4 P5.3 P0.5/AD5 P0.6/AD6 P0.7/AD7 64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 NIC ALE PSEN# P2.7/A15 P2.6/A14 P5.2 P5.1 P2.5/A13 P5.0 EA P5.5 P0.3/AD3 P0.2/AD2 P5.6 P0.1/AD1 P0.0/AD0 P5.7 VCC NIC P1.0/T2 P4.0 P1.1/T2EX/SS P1.2/ECI P1.3/CEX0 P4.1 P1.4/CEX1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 AT89C51ED2 VQFP64 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 P2.4/A12 P2.3/A11 P4.7 P2.2/A10 P2.1/A9 P2.0/A8 P4.6 NIC VSS P4.5 XTAL1 XTAL2 P3.7/RD P4.4 P3.6/WR P4.3 10 AT89C51RD2/ED2 4235K–8051–05/08 P4.2 17 P1.5/CEX2/MISO 18 P1.6/CEX3/SCK 19 P1.7/A17/CEX4/MOSI 20 RST 21 NIC 22 NIC 23 NIC 24 P3.0/RxD 25 NIC 26 27 NIC P3.1/TxD 28 29 P3.2/INT0 P3.3/INT1 30 P3.4/T0 31 P3.5/T1 32 P1.5/CEX2/MISO27 P1.6/CEX3/SCK28 P1.7/CEX4/MOSI29 RST 30 NIC 31 NIC 32 NIC 33 P3.0/RxD 34 NIC 35 NIC 36 NIC 37 NIC 38 P3.1/TxD 39 P3.2/INT0 40 P3.3/INT1 41 P3.4/T0 42 P3.5/T1 43 PSEN AT89C51RD2/ED2 Table 4-1. Pin Description Pin Number Type Mnemonic VSS VCC PLCC44 VQFP44 22 44 16 38 PLCC68 51 17 VQFP64 40 8 I I Name and Function Ground: 0V reference Power Supply: This is the power supply voltage for normal, idle and power-down operation Port 0: Port 0 is an open-drain, bidirectional I/O port. Port 0 pins that have 1s written to them float and can be used as high impedance inputs. Port 0 must be polarized to VCC or VSS in order to prevent any parasitic current consumption. Port 0 is also the multiplexed low-order address and data bus during access to external program and data memory. In this application, it uses strong internal pull-up when emitting 1s. Port 0 also inputs the code bytes during EPROM programming. External pull-ups are required during program verification during which P0 outputs the code bytes. Port 1: Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. Port 1 pins that have 1s written to them are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally pulled low will source current because of the internal pull-ups. Port 1 also receives the low-order address byte during memory programming and verification. Alternate functions for AT89C51RD2/ED2 Port 1 include: 2 40 19 10 I/O I/O 3 41 21 12 I/O I I 4 42 22 13 I/O I 5 43 23 14 I/O I/O 6 44 25 16 I/O I/O 7 1 27 18 I/O I/O I/O P1.0: Input/Output T2 (P1.0): Timer/Counter 2 external count input/Clockout P1.1: Input/Output T2EX: Timer/Counter 2 Reload/Capture/Direction Control SS: SPI Slave Select P1.2: Input/Output ECI: External Clock for the PCA P1.3: Input/Output CEX0: Capture/Compare External I/O for PCA module 0 P1.4: Input/Output CEX1: Capture/Compare External I/O for PCA module 1 P1.5: Input/Output CEX2: Capture/Compare External I/O for PCA module 2 MISO: SPI Master Input Slave Output line When SPI is in master mode, MISO receives data from the slave peripheral. When SPI is in slave mode, MISO outputs data to the master controller. 8 2 28 19 I/O I/O I/O P1.6: Input/Output CEX3: Capture/Compare External I/O for PCA module 3 SCK: SPI Serial Clock P0.0 - P0.7 43 - 36 37 - 30 15, 14, 12, 11, 9,6, 5, 3 6, 5, 3, 2, 64, 61,60,59 I/O P1.0 - P1.7 2-9 40 - 44 1-3 19, 21, 22, 23, 25, 27, 28, 29 10, 12, 13, 14, 16, 18, 19, 20 I/O 11 4235K–8051–05/08 Table 4-1. Pin Description (Continued) Pin Number Type Mnemonic PLCC44 VQFP44 9 3 PLCC68 29 VQFP64 20 I/O I/O I/O Name and Function P1.7: Input/Output: CEX4: Capture/Compare External I/O for PCA module 4 MOSI: SPI Master Output Slave Input line When SPI is in master mode, MOSI outputs data to the slave peripheral. When SPI is in slave mode, MOSI receives data from the master controller. XTALA1 XTALA2 21 20 15 14 49 48 38 37 I O XTALA 1: Input to the inverting oscillator amplifier and input to the internal clock generator circuits. XTALA 2: Output from the inverting oscillator amplifier Port 2: Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. Port 2 pins that have 1s written to them are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally pulled low will source current because of the internal pull-ups. 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-ups emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX @Ri), port 2 emits the contents of the P2 SFR. Port 3: Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. Port 3 pins that have 1s written to them are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally pulled low will source current because of the internal pull-ups. Port 3 also serves the special features of the 80C51 family, as listed below. RXD (P3.0): Serial input port TXD (P3.1): Serial output port INT0 (P3.2): External interrupt 0 INT1 (P3.3): External interrupt 1 T0 (P3.4): Timer 0 external input T1 (P3.5): Timer 1 external input WR (P3.6): External data memory write strobe RD (P3.7): External data memory read strobe Port 4: Port 4 is an 8-bit bidirectional I/O port with internal pull-ups. Port 3 pins that have 1s written to them are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally pulled low will source current because of the internal pull-ups. Port 5: Port 5 is an 8-bit bidirectional I/O port with internal pull-ups. Port 3 pins that have 1s written to them are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally pulled low will source current because of the internal pull-ups. Reset: A high on this pin for two machine cycles while the oscillator is running, resets the device. An internal diffused resistor to VSS permits a power-on reset using only an external capacitor to VCC. This pin is an output when the hardware watchdog forces a system reset. P2.0 - P2.7 24 - 31 18 - 25 54, 55, 56, 58, 59, 61, 64, 65 43, 44, 45, 47, 48, 50, 53, 54 I/O P3.0 - P3.7 11, 13 - 19 5, 7 - 13 34, 39, 40, 41, 42, 43, 45, 47 25, 28, 29, 30, 31, 32, 34, 36 I/O 11 13 14 15 16 17 18 19 5 7 8 9 10 11 12 13 34 39 40 41 42 43 45 47 20, 24, 26, 44, 46, 50, 53, 57 25 28 29 30 31 32 34 36 11, 15, 17,33, 35,39, 42, 46 I O I I I I O O P4.0 - P4.7 - - I/O P5.0 - P5.7 - - 60, 62, 49, 51, 63, 7, 8, 52, 62, 10, 13, 16 63, 1, 4, 7 I/O RST 10 4 30 21 I 12 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 4-1. Pin Description (Continued) Pin Number Type Mnemonic ALE/PRO G PLCC44 VQFP44 33 27 PLCC68 68 VQFP64 56 O (I) Name and Function Address Latch Enable/Program Pulse: Output pulse for latching the low byte of the address during an access to external memory. In normal operation, ALE is emitted at a constant rate of 1/6 (1/3 in X2 mode) the oscillator frequency, and can be used for external timing or clocking. Note that one ALE pulse is skipped during each access to external data memory. This pin is also the program pulse input (PROG) during Flash programming. ALE can be disabled by setting SFR’s AUXR.0 bit. With this bit set, ALE will be inactive during internal fetches. Program Strobe ENable: The read strobe to external program memory. When executing code from the external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory. PSEN is not activated during fetches from internal program memory. External Access Enable: EA must be externally held low to enable the device to fetch code from external program memory locations 0000H to FFFFH. If security level 1 is programmed, EA will be internally latched on Reset. PSEN 32 26 67 55 O EA 35 29 2 58 I 13 4235K–8051–05/08 5. Port Types AT89C51RD2/ED2 I/O ports (P1, P2, P3, P4, P5) implement the quasi-bidirectional output that is common on the 80C51 and most of its derivatives. This output type can be used as both an input and output without the need to reconfigure the port. This is possible because when the port outputs a logic high, it is weakly driven, allowing an external device to pull the pin low. When the pin is pulled low, it is driven strongly and able to sink a fairly large current. These features are somewhat similar to an open drain output except that there are three pull-up transistors in the quasi-bidirectional output that serve different purposes. One of these pull-ups, called the "weak" pull-up, is turned on whenever the port latch for the pin contains a logic 1. The weak pull-up sources a very small current that will pull the pin high if it is left floating. A second pull-up, called the "medium" pull-up, is turned on when the port latch for the pin contains a logic 1 and the pin itself is also at a logic 1 level. This pull-up provides the primary source current for a quasi-bidirectional pin that is outputting a 1. If a pin that has a logic 1 on it is pulled low by an external device, the medium pull-up turns off, and only the weak pull-up remains on. In order to pull the pin low under these conditions, the external device has to sink enough current to overpower the medium pull-up and take the voltage on the port pin below its input threshold. The third pull-up is referred to as the "strong" pull-up. This pull-up is used to speed up low-tohigh transitions on a quasi-bidirectional port pin when the port latch changes from a logic 0 to a logic 1. When this occurs, the strong pull-up turns on for a brief time, two CPU clocks, in order to pull the port pin high quickly. Then it turns off again. The DPU bit (bit 7 in AUXR register) allows to disable the permanent weak pull up of all ports when latch data is logical 0. The quasi-bidirectional port configuration is shown in Figure 5-1. Figure 5-1. Quasi-Bidirectional Output 2 CPU Clock Delay P Strong P Weak P Medium Pin Port Latch Data N DPU AUXR.7 Input Data 14 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 6. Oscillator To optimize the power consumption and execution time needed for a specific task, an internal prescaler feature has been implemented between the oscillator and the CPU and peripherals. 6.1 Registers Table 6-1. CKRL Register CKRL – Clock Reload Register (97h) 7 CKRL7 Bit Number 7:0 6 CKRL6 5 CKRL5 Mnemonic CKRL 4 CKRL4 Description Clock Reload Register Prescaler value 3 CKRL3 2 CKRL2 1 CKRL1 0 CKRL0 Reset Value = 1111 1111b Not bit addressable Table 6-2. PCON Register PCON – Power Control Register (87h) 7 SMOD1 Bit Number 7 6 SMOD0 5 4 POF Description Serial Port Mode bit 1 Set to select double baud rate in mode 1, 2 or 3. Serial Port Mode bit 0 Cleared to select SM0 bit in SCON register. Set to select FE bit in SCON register. Reserved The value read from this bit is indeterminate. Do not set this bit. Power-off Flag Cleared by software to recognize the next reset type. Set by hardware when VCC rises from 0 to its nominal voltage. Can also be set by software. General-purpose Flag Cleared by software for general-purpose usage. Set by software for general-purpose usage. General-purpose Flag Cleared by software for general-purpose usage. Set by software for general-purpose usage. Power-down Mode bit Cleared by hardware when reset occurs. Set to enter power-down mode. Idle Mode bit Cleared by hardware when interrupt or reset occurs. Set to enter idle mode. 3 GF1 2 GF0 1 PD 0 IDL Bit Mnemonic SMOD1 6 SMOD0 5 - 4 POF 3 GF1 2 GF0 1 PD 0 IDL Reset Value = 00X1 0000b Not bit addressable 15 4235K–8051–05/08 6.2 Functional Block Diagram Functional Oscillator Block Diagram Reset CKRL Xtal1 Osc Xtal2 :2 FOSC 1 0 8-bit Prescaler-Divider 1 X2 CLK Periph CLK CPU Peripheral Clock CPU Clock Reload Figure 6-1. CKCON0 0 Idle CKRL = 0xFF? 6.2.1 Prescaler Divider • A hardware RESET puts the prescaler divider in the following state: • CKRL = FFh: FCLK CPU = FCLK PERIPH = FOSC/2 (Standard C51 feature) • Any value between FFh down to 00h can be written by software into CKRL register in order to divide frequency of the selected oscillator: • CKRL = 00h: minimum frequency FCLK CPU = FCLK PERIPH = FOSC/1020 (Standard Mode) FCLK CPU = FCLK PERIPH = FOSC/510 (X2 Mode) CKRL = FFh: maximum frequency FCLK CPU = FCLK PERIPH = FOSC/2 (Standard Mode) FCLK CPU = FCLK PERIPH = FOSC (X2 Mode) • FCLK CPU and FCLK PERIPH In X2 Mode, for CKRL0xFF: F OSC F CPU = F CLKPERIPH = ---------------------------------------------- 2 × ( 255 – CKRL ) In X1 Mode, for CKRL0xFF then: F OSC F CPU = F CLKPERIPH = ---------------------------------------------- 4 × ( 255 – CKRL ) 16 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 7. Enhanced Features In comparison to the original 80C52, the AT89C51RD2/ED2 implements some new features, which are: • X2 option • Dual Data Pointer • Extended RAM • Programmable Counter Array (PCA) • Hardware Watchdog • SPI interface • 4-level interrupt priority system • Power-off flag • ONCE mode • ALE disabling • Some enhanced features are also located in the UART and the Timer 2 7.1 X2 Feature The AT89C51RD2/ED2 core needs only 6 clock periods per machine cycle. This feature called ‘X2’ provides the following advantages: • Divide frequency crystals by 2 (cheaper crystals) while keeping same CPU power. • Save power consumption while keeping same CPU power (oscillator power saving). • Save power consumption by dividing dynamically the operating frequency by 2 in operating and idle modes. • Increase CPU power by 2 while keeping same crystal frequency. In order to keep the original C51 compatibility, a divider by 2 is inserted between the XTAL1 signal and the main clock input of the core (phase generator). This divider may be disabled by software. 7.1.1 Description The clock for the whole circuit and peripherals is first divided by two before being used by the CPU core and the peripherals. This allows any cyclic ratio to be accepted on XTAL1 input. In X2 mode, as this divider is bypassed, the signals on XTAL1 must have a cyclic ratio between 40 to 60%. Figure 7-1 shows the clock generation block diagram. X2 bit is validated on the rising edge of the XTAL1 ÷ 2 to avoid glitches when switching from X2 to STD mode. Figure 7-2 shows the switching mode waveforms. 17 4235K–8051–05/08 Figure 7-1. Clock Generation Diagram CKRL XTAL1 FXTAL 2 XTAL1:2 0 1 FOSC 8-bit Prescaler FCLK CPU FCLK PERIPH X2 CKCON0 Figure 7-2. Mode Switching Waveforms XTAL1 XTAL1:2 X2 Bit CPU Clock STD Mode FOSC X2 Mode STD Mode The X2 bit in the CKCON0 register (see Table 7-1) allows a switch from 12 clock periods per instruction to 6 clock periods and vice versa. At reset, the speed is set according to X2 bit of Hardware Security Byte (HSB). By default, Standard mode is active. Setting the X2 bit activates the X2 feature (X2 mode). The T0X2, T1X2, T2X2, UartX2, PcaX2, and WdX2 bits in the CKCON0 register (Table 7-1) and SPIX2 bit in the CKCON1 register (see Table 7-2) allows a switch from standard peripheral speed (12 clock periods per peripheral clock cycle) to fast peripheral speed (6 clock periods per peripheral clock cycle). These bits are active only in X2 mode. Table 7-1. CKCON0 Register CKCON0 - Clock Control Register (8Fh) 7 Bit Number 7 6 WDX2 Bit Mnemonic Reserved Description The values for this bit are indeterminite. Do not set this bit. Watchdog Clock 6 WDX2 (This control bit is validated when the CPU clock X2 is set; when X2 is low, this bit has no effect). Cleared to select 6 clock periods per peripheral clock cycle. Set to select 12 clock periods per peripheral clock cycle. 5 PCAX2 4 SIX2 3 T2X2 2 T1X2 1 T0X2 0 X2 18 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Bit Number Bit Mnemonic Description Programmable Counter Array Clock 5 PCAX2 (This control bit is validated when the CPU clock X2 is set; when X2 is low, this bit has no effect). Cleared to select 6 clock periods per peripheral clock cycle. Set to select 12 clock periods per peripheral clock cycle. Enhanced UART Clock (Mode 0 and 2) 4 SIX2 (This control bit is validated when the CPU clock X2 is set; when X2 is low, this bit has no effect). Cleared to select 6 clock periods per peripheral clock cycle. Set to select 12 clock periods per peripheral clock cycle. Timer2 Clock 3 T2X2 (This control bit is validated when the CPU clock X2 is set; when X2 is low, this bit has no effect). Cleared to select 6 clock periods per peripheral clock cycle. Set to select 12 clock periods per peripheral clock cycle. Timer1 Clock 2 T1X2 (This control bit is validated when the CPU clock X2 is set; when X2 is low, this bit has no effect). Cleared to select 6 clock periods per peripheral clock cycle. Set to select 12 clock periods per peripheral clock cycle. Timer0 Clock 1 T0X2 (This control bit is validated when the CPU clock X2 is set; when X2 is low, this bit has no effect). Cleared to select 6 clock periods per peripheral clock cycle. Set to select 12 clock periods per peripheral clock cycle. CPU Clock 0 X2 Cleared to select 12 clock periods per machine cycle (STD mode) for CPU and all the peripherals. Set to select 6 clock periods per machine cycle (X2 mode) and to enable the individual peripherals’X2’ bits. Programmed by hardware after Power-up regarding Hardware Security Byte (HSB), Default setting, X2 is cleared. Reset Value = 0000 000’HSB. X2’b (See “Hardware Security Byte”) Not bit addressable Table 7-2. CKCON1 Register CKCON1 - Clock Control Register (AFh) 7 Bit Number 7 6 5 4 3 6 Bit Mnemonic Description Reserved Reserved Reserved Reserved Reserved 5 4 3 2 1 0 SPIX2 19 4235K–8051–05/08 Bit Number 2 1 Bit Mnemonic Description Reserved Reserved SPI (This control bit is validated when the CPU clock X2 is set; when X2 is low, this bit has no effect). Clear to select 6 clock periods per peripheral clock cycle. Set to select 12 clock periods per peripheral clock cycle. 0 SPIX2 Reset Value = XXXX XXX0b Not bit addressable 20 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 8. Dual Data Pointer Register (DPTR) The additional data pointer can be used to speed up code execution and reduce code size. The dual DPTR structure is a way by which the chip will specify the address of an external data memory location. There are two 16-bit DPTR registers that address the external memory, and a single bit called DPS = AUXR1.0 (see Table 8-1) that allows the program code to switch between them (Refer to Figure 8-1). Figure 8-1. Use of Dual Pointer External Data Memory 7 0 DPS DPTR1 DPTR0 AUXR1(A2H) DPH(83H) DPL(82H) Table 8-1. AUXR1 Register AUXR1- Auxiliary Register 1(0A2h) 7 Bit Number 7 6 Bit Mnemonic Description Reserved The value read from this bit is indeterminate. Do not set this bit. Reserved The value read from this bit is indeterminate. Do not set this bit. Enable Boot Flash Cleared to disable boot ROM. Set to map the boot ROM between F800h - 0FFFFh. 4 3 2 1 GF3 0 Reserved The value read from this bit is indeterminate. Do not set this bit. This bit is a general-purpose user flag.(1) Always cleared Reserved The value read from this bit is indeterminate. Do not set this bit. Data Pointer Selection Cleared to select DPTR0. Set to select DPTR1. 5 ENBOOT 4 3 GF3 2 0 1 0 DPS 6 - 5 ENBOOT 0 DPS 21 4235K–8051–05/08 Reset Value = XXXX XX0X0b Not bit addressable Note: 1. Bit 2 stuck at 0; this allows to use INC AUXR1 to toggle DPS without changing GF3. ASSEMBLY LANGUAGE ; Block move using dual data pointers ; Modifies DPTR0, DPTR1, A and PSW ; note: DPS exits opposite of entry state ; unless an extra INC AUXR1 is added ; 00A2 AUXR1 EQU 0A2H ; 0000 909000MOV DPTR,#SOURCE ; address of SOURCE 0003 05A2 INC AUXR1 ; switch data pointers 0005 90A000 MOV DPTR,#DEST ; address of DEST 0008 LOOP: 0008 05A2 INC AUXR1 ; switch data pointers 000A E0 MOVX A,@DPTR ; get a byte from SOURCE 000B A3 INC DPTR ; increment SOURCE address 000C 05A2 INC AUXR1 ; switch data pointers 000E F0 MOVX @DPTR,A ; write the byte to DEST 000F A3 INC DPTR ; increment DEST address 0010 70F6JNZ LOOP ; check for 0 terminator 0012 05A2 INC AUXR1 ; (optional) restore DPS INC is a short (2 bytes) and fast (12 clocks) way to manipulate the DPS bit in the AUXR1 SFR. However, note that the INC instruction does not directly force the DPS bit to a particular state, but simply toggles it. In simple routines, such as the block move example, only the fact that DPS is toggled in the proper sequence matters, not its actual value. In other words, the block move routine works the same whether DPS is '0' or '1' on entry. Observe that without the last instruction (INC AUXR1), the routine will exit with DPS in the opposite state. 22 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 9. Expanded RAM (XRAM) The AT89C51RD2/ED2 provides additional on-chip random access memory (RAM) space for increased data parameter handling and high level language usage. AT89C51RD2/ED2 device haS expanded RAM in external data space configurable up to 1792 bytes (see Table 9-1). The AT89C51RD2/ED2 internal data memory is mapped into four separate segments. The four segments are: 1. The Lower 128 bytes of RAM (addresses 00h to 7Fh) are directly and indirectly addressable. 2. The Upper 128 bytes of RAM (addresses 80h to FFh) are indirectly addressable only. 3. The Special Function Registers, SFRs, (addresses 80h to FFh) are directly addressable only. 4. The expanded RAM bytes are indirectly accessed by MOVX instructions, and with the EXTRAM bit cleared in the AUXR register (see Table 9-1). The lower 128 bytes can be accessed by either direct or indirect addressing. The Upper 128 bytes can be accessed by indirect addressing only. The Upper 128 bytes occupy the same address space as the SFR. That means they have the same address, but are physically separate from SFR space. Figure 9-1. Internal and External Data Memory Address 0FFh or 6FFh 0FFh Upper 128 Bytes Internal RAM Indirect Accesses XRAM 80h 7Fh Lower 128 Bytes Internal RAM Direct or Indirect Accesses 00 00 80h 0FFh 0FFFFh Special Function Register Direct Accesses External Data Memory 00FFh up to 06FFh 0000 When an instruction accesses an internal location above address 7Fh, the CPU knows whether the access is to the upper 128 bytes of data RAM or to SFR space by the addressing mode used in the instruction. • Instructions that use direct addressing access SFR space. For example: MOV 0A0H, # data, accesses the SFR at location 0A0h (which is P2). • Instructions that use indirect addressing access the Upper 128 bytes of data RAM. For example: MOV @R0, # data where R0 contains 0A0h, accesses the data byte at address 0A0h, rather than P2 (whose address is 0A0h). • The XRAM bytes can be accessed by indirect addressing, with EXTRAM bit cleared and MOVX instructions. This part of memory which is physically located on-chip, logically occupies the first bytes of external data memory. The bits XRS0 and XRS1 are used to hide a 23 4235K–8051–05/08 part of the available XRAM as explained in Table 9-1. This can be useful if external peripherals are mapped at addresses already used by the internal XRAM. • With EXTRAM = 0, the XRAM is indirectly addressed, using the MOVX instruction in combination with any of the registers R0, R1 of the selected bank or DPTR. An access to XRAM will not affect ports P0, P2, P3.6 (WR) and P3.7 (RD). For example, with EXTRAM = 0, MOVX @R0, # data where R0 contains 0A0H, accesses the XRAM at address 0A0H rather than external memory. An access to external data memory locations higher than the accessible size of the XRAM will be performed with the MOVX DPTR instructions in the same way as in the standard 80C51, with P0 and P2 as data/address busses, and P3.6 and P3.7 as write and read timing signals. Accesses to XRAM above 0FFH can only be done by the use of DPTR. • With EXTRAM = 1, MOVX @Ri and MOVX @DPTR will be similar to the standard 80C51.MOVX @ Ri will provide an eight-bit address multiplexed with data on Port0 and any output port pins can be used to output higher order address bits. This is to provide the external paging capability. MOVX @DPTR will generate a sixteen-bit address. Port2 outputs the high-order eight address bits (the contents of DPH) while Port0 multiplexes the low-order eight address bits (DPL) with data. MOVX @ Ri and MOVX @DPTR will generate either read or write signals on P3.6 (WR) and P3.7 (RD). The stack pointer (SP) may be located anywhere in the 256 bytes RAM (lower and upper RAM) internal data memory. The stack may not be located in the XRAM. The M0 bit allows to stretch the XRAM timings; if M0 is set, the read and write pulses are extended from 6 to 30 clock periods. This is useful to access external slow peripherals. 9.1 Registers Table 9-1. AUXR Register AUXR - Auxiliary Register (8Eh) 7 DPU Bit Number 6 Bit Mnemonic Description Disable Weak Pull-up 7 DPU Cleared by software to activate the permanent weak pull-up (default) Set by software to disable the weak pull-up (reduce power consumption) 6 Reserved The value read from this bit is indeterminate. Do not set this bit. Pulse length 5 M0 Cleared to stretch MOVX control: the RD and the WR pulse length is 6 clock periods (default). Set to stretch MOVX control: the RD and the WR pulse length is 30 clock periods. 4 3 XRS2 XRS1 XRAM Size XRS2XRS1XRS0XRAM size 00 0256 bytes 0 2 XRS0 0 0 1 0 1 1 0 1 512 bytes 0768 bytes(default) 11024 bytes 01792 bytes 5 M0 4 XRS2 3 XRS1 2 XRS0 1 EXTRAM 0 AO 24 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Bit Number Bit Mnemonic Description EXTRAM bit Cleared to access internal XRAM using movx @ Ri/ @ DPTR. 1 EXTRAM Set to access external memory. Programmed by hardware after Power-up regarding Hardware Security Byte (HSB), default setting, XRAM selected. ALE Output bit Cleared, ALE is emitted at a constant rate of 1/6 the oscillator frequency (or 1/3 if X2 mode is used). (default) Set, ALE is active only during a MOVX or MOVC instruction is used. 0 AO Reset Value = 0X00 1000 Not bit addressable 25 4235K–8051–05/08 10. Reset 10.1 Introduction The reset sources are: Power Management, Hardware Watchdog, PCA Watchdog and Reset input. Figure 10-1. Reset schematic Power Monitor Hardware Watchdog PCA Watchdog Internal Reset RST 10.2 Reset Input The Reset input can be used to force a reset pulse longer than the internal reset controlled by the Power Monitor. RST input has a pull-down resistor allowing power-on reset by simply connecting an external capacitor to V CC a s shown in Figure 10-2. Resistor value and input characteristics are discussed in the Section “DC Characteristics” of the AT89C51RD2/ED2 datasheet. Figure 10-2. Reset Circuitry and Power-On Reset VDD RST R To internal reset + RST RST VSS a. RST input circuitry b. Power-on Reset 10.3 Reset Output Reset output can be generated by two sources: • Internal POR/PFD • Hardware watchdog timer As detailed in Section “Hardware Watchdog Timer”, page 84, the WDT generates a 96-clock period pulse on the RST pin. In order to properly propagate this pulse to the rest of the application in case of external capacitor or power-supply supervisor circuit, a 1 kΩ resistor must be added as shown Figure 10-3. 26 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Figure 10-3. Recommended Reset Output Schematic VDD + RST VDD 1K AT89C51XD2 RST VSS To other on-board circuitry 27 4235K–8051–05/08 11. Power Monitor The POR/PFD function monitors the internal power-supply of the CPU core memories and the peripherals, and if needed, suspends their activity when the internal power supply falls below a safety threshold. This is achieved by applying an internal reset to them. By generating the Reset the Power Monitor insures a correct start up when AT89C51RD2/ED2 is powered up. 11.1 Description In order to startup and maintain the microcontroller in correct operating mode, VCC has to be stabilized in the VCC operating range and the oscillator has to be stabilized with a nominal amplitude compatible with logic level VIH/VIL. These parameters are controlled during the three phases: power-up, normal operation and power going down. See Figure 11-1. Figure 11-1. Power Monitor Block Diagram VCC CPU core Power On Reset Power Fail Detect Voltage Regulator Regulated Supply Memories Peripherals XTAL1 (1) Internal Reset RST pin PCA Watchdog Hardware Watchdog Note: 1. Once XTAL1 High and low levels reach above and below VIH/VIL. a 1024 clock period delay will extend the reset coming from the Power Fail Detect. If the power falls below the Power Fail Detect threshold level, the Reset will be applied immediately. The Voltage regulator generates a regulated internal supply for the CPU core the memories and the peripherals. Spikes on the external Vcc are smoothed by the voltage regulator. The Power fail detect monitor the supply generated by the voltage regulator and generate a reset if this supply falls below a safety threshold as illustrated in the Figure 11-2 below. 28 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Figure 11-2. Power Fail Detect Vcc VPFDP VPFDM t Reset Vcc When the power is applied, the Power Monitor immediately asserts a reset. Once the internal supply after the voltage regulator reach a safety level, the power monitor then looks at the XTAL clock input. The internal reset will remain asserted until the Xtal1 levels are above and below VIH and VIL. Further more. An internal counter will count 1024 clock periods before the reset is de-asserted. If the internal power supply falls below a safety level, a reset is immediately asserted. . 29 4235K–8051–05/08 12. Timer 2 The Timer 2 in the AT89C51RD2/ED2 is the standard C52 Timer 2. It is a 16-bit timer/counter: the count is maintained by two eight-bit timer registers, TH2 and TL2 are cascaded. It is controlled by T2CON (Table 12-1) and T2MOD (Table 12-2) registers. Timer 2 operation is similar to Timer 0 and Timer 1. C/T2 selects FOSC/12 (timer operation) or external pin T2 (counter operation) as the timer clock input. Setting TR2 allows TL2 to increment by the selected input. Timer 2 has 3 operating modes: capture, autoreload and Baud Rate Generator. These modes are selected by the combination of RCLK, TCLK and CP/RL2 (T2CON). Refer to the Atmel 8-bit Microcontroller Hardware Manual for the description of Capture and Baud Rate Generator Modes. Timer 2 includes the following enhancements: • Auto-reload mode with up or down counter • Programmable clock-output 12.1 Auto-reload Mode The auto-reload mode configures Timer 2 as a 16-bit timer or event counter with automatic reload. If DCEN bit in T2MOD is cleared, Timer 2 behaves as in 80C52 (refer to the Atmel C51 Microcontroller Hardware Manual). If DCEN bit is set, Timer 2 acts as an Up/down timer/counter as shown in Figure 12-1. In this mode the T2EX pin controls the direction of count. When T2EX is high, Timer 2 counts up. Timer overflow occurs at FFFFh which sets the TF2 flag and generates an interrupt request. The overflow also causes the 16-bit value in RCAP2H and RCAP2L registers to be loaded into the timer registers TH2 and TL2. When T2EX is low, Timer 2 counts down. Timer underflow occurs when the count in the timer registers TH2 and TL2 equals the value stored in RCAP2H and RCAP2L registers. The underflow sets TF2 flag and reloads FFFFh into the timer registers. The EXF2 bit toggles when Timer 2 overflows or underflows according to the direction of the count. EXF2 does not generate any interrupt. This bit can be used to provide 17-bit resolution. 30 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Figure 12-1. Auto-reload Mode Up/Down Counter (DCEN = 1) FCLK PERIPH :6 T2 C/T2 T2CON TR2 T2CON 0 1 (DOWN COUNTING RELOAD VALUE) T2EX: If DCEN = 1, 1 = UP FFh FFh If DCEN = 1, 0 = DOWN (8-bit) (8-bit) If DCEN = 0, up counting TOGGLE T2CON EXF2 TL2 (8-bit) TH2 (8-bit) TF2 T2CON TIMER 2 INTERRUPT RCAP2L (8-bit) RCAP2H (8-bit) (UP COUNTING RELOAD VALUE) 12.2 Programmable Clock-output In the clock-out mode, Timer 2 operates as a 50% duty-cycle, programmable clock generator (See Figure 12-2). The input clock increments TL2 at frequency FCLK PERIPH/2. The timer repeatedly counts to overflow from a loaded value. At overflow, the contents of RCAP2H and RCAP2L registers are loaded into TH2 and TL2. In this mode, Timer 2 overflows do not generate interrupts. The formula gives the clock-out frequency as a function of the system oscillator frequency and the value in the RCAP2H and RCAP2L registers: F CLKPERIPH C lock – O utFrequency = -------------------------------------------------------------------------------------------4 × ( 65536 – RCAP 2 H ⁄ RCAP 2 L ) For a 16 MHz system clock, Timer 2 has a programmable frequency range of 61 Hz (FCLK PERIPH/216) to 4 MHz (FCLK PERIPH/4). The generated clock signal is brought out to T2 pin (P1.0). Timer 2 is programmed for the clock-out mode as follows: • Set T2OE bit in T2MOD register. • Clear C/T2 bit in T2CON register. • Determine the 16-bit reload value from the formula and enter it in RCAP2H/RCAP2L registers. • Enter a 16-bit initial value in timer registers TH2/TL2. It can be the same as the reload value or a different one depending on the application. • To start the timer, set TR2 run control bit in T2CON register. 31 4235K–8051–05/08 It is possible to use Timer 2 as a baud rate generator and a clock generator simultaneously. For this configuration, the baud rates and clock frequencies are not independent since both functions use the values in the RCAP2H and RCAP2L registers. Figure 12-2. Clock-out Mode C/T2 = 0 FCLK PERIPH :6 TR2 T2CON TL2 (8-bit) TH2 (8-bit) OVERFLOW RCAP2L RCAP2H (8-bit) (8-bit) Toggle T2 Q D T2OE T2MOD EXF2 TIMER 2 INTERRUPT T2EX EXEN2 T2CON T2CON 12.3 Registers Table 12-1. T2CON Register T2CON - Timer 2 Control Register (C8h) 7 TF2 6 EXF2 5 RCLK 4 TCLK 3 EXEN2 2 TR2 1 C/T2# 0 CP/RL2# 32 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Bit Number Bit Mnemonic Description Timer 2 overflow Flag Must be cleared by software. Set by hardware on Timer 2 overflow, if RCLK = 0 and TCLK = 0. Timer 2 External Flag Set when a capture or a reload is caused by a negative transition on T2EX pin if EXEN2 = 1. When set, causes the CPU to vector to Timer 2 interrupt routine when Timer 2 interrupt is enabled. Must be cleared by software. EXF2 doesn’t cause an interrupt in Up/down counter mode (DCEN = 1). Receive Clock bit Cleared to use timer 1 overflow as receive clock for serial port in mode 1 or 3. Set to use Timer 2 overflow as receive clock for serial port in mode 1 or 3. Transmit Clock bit Cleared to use timer 1 overflow as transmit clock for serial port in mode 1 or 3. Set to use Timer 2 overflow as transmit clock for serial port in mode 1 or 3. Timer 2 External Enable bit Cleared to ignore events on T2EX pin for Timer 2 operation. Set to cause a capture or reload when a negative transition on T2EX pin is detected, if Timer 2 is not used to clock the serial port. Timer 2 Run control bit Cleared to turn off Timer 2. Set to turn on Timer 2. Timer/Counter 2 select bit Cleared for timer operation (input from internal clock system: FCLK PERIPH). Set for counter operation (input from T2 input pin, falling edge trigger). Must be 0 for clock out mode. Timer 2 Capture/Reload bit If RCLK = 1 or TCLK = 1, CP/RL2# is ignored and timer is forced to auto-reload on Timer 2 overflow. Cleared to auto-reload on Timer 2 overflows or negative transitions on T2EX pin if EXEN2=1. Set to capture on negative transitions on T2EX pin if EXEN2 = 1. 7 TF2 6 EXF2 5 RCLK 4 TCLK 3 EXEN2 2 TR2 1 C/T2# 0 CP/RL2# Reset Value = 0000 0000b Bit addressable 33 4235K–8051–05/08 Table 12-2. T2MOD Register T2MOD - Timer 2 Mode Control Register (C9h) 7 Bit Number 7 6 Bit Mnemonic Description Reserved The value read from this bit is indeterminate. Do not set this bit. Reserved The value read from this bit is indeterminate. Do not set this bit. Reserved The value read from this bit is indeterminate. Do not set this bit. Reserved The value read from this bit is indeterminate. Do not set this bit. Reserved The value read from this bit is indeterminate. Do not set this bit. Reserved The value read from this bit is indeterminate. Do not set this bit. Timer 2 Output Enable bit Cleared to program P1.0/T2 as clock input or I/O port. Set to program P1.0/T2 as clock output. Down Counter Enable bit Cleared to disable Timer 2 as up/down counter. Set to enable Timer 2 as up/down counter. 5 4 3 2 1 T2OE 0 DCEN 6 - 5 - 4 - 3 - 2 - 1 T2OE 0 DCEN Reset Value = XXXX XX00b Not bit addressable 34 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 13. Programmable Counter Array (PCA) The PCA provides more timing capabilities with less CPU intervention than the standard timer/counters. Its advantages include reduced software overhead and improved accuracy. The PCA consists of a dedicated timer/counter which serves as the time base for an array of five compare/capture modules. Its clock input can be programmed to count any one of the following signals: • Peripheral clock frequency (FCLK PERIPH) • Timer 0 overflow • External input on ECI (P1.2) Each compare/capture module can be programmed in any one of the following modes: • Rising and/or falling edge capture • Software timer • High-speed output • Pulse width modulator Module 4 can also be programmed as a watchdog timer (see Section "PCA Watchdog Timer", page 46). When the compare/capture modules are programmed in the capture mode, software timer, or high speed output mode, an interrupt can be generated when the module executes its function. All five modules plus the PCA timer overflow share one interrupt vector. The PCA timer/counter and compare/capture modules share Port 1 for external I/O. These pins are listed below. If one or several bits in the port are not used for the PCA, they can still be used for standard I/O. PCA Component 16-bit Counter 16-bit Module 0 16-bit Module 1 16-bit Module 2 16-bit Module 3 External I/O Pin P1.2/ECI P1.3/CEX0 P1.4/CEX1 P1.5/CEX2 P1.6/CEX3 ÷6 • Peripheral clock frequency (FCLK PERIPH) ÷ 2 The PCA timer is a common time base for all five modules (see Figure 13-1). The timer count source is determined from the CPS1 and CPS0 bits in the CMOD register (Table 13-1) and can be programmed to run at: • 1/6 the peripheral clock frequency (FCLK PERIPH) • 1/2 the peripheral clock frequency (FCLK PERIPH) • The Timer 0 overflow • The input on the ECI pin (P1.2) The CMOD register includes three additional bits associated with the PCA (See Figure 13-1 and Table 13-1). • The CIDL bit which allows the PCA to stop during idle mode. • The WDTE bit which enables or disables the watchdog function on module 4. 35 4235K–8051–05/08 • The ECF bit which when set causes an interrupt and the PCA overflow flag CF (in the CCON SFR) to be set when the PCA timer overflows. Figure 13-1. PCA Timer/Counter To PCA Modules FCLK PERIPH/6 FCLK PERIPH/2 T0 OVF P1.2 Overflow CH CL 16 Bit Up Counter IT CIDL Idle WDTE CPS1 CPS0 ECF CMOD 0xD9 CF CR CCF4 CCF3 CCF2 CCF1 CCF0 CCON 0xD8 36 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 13-1. CMOD Register CMOD - PCA Counter Mode Register (D9h) 7 CIDL Bit Number 6 WDTE Bit Mnemonic Description Counter Idle Control 7 CIDL Cleared to program the PCA Counter to continue functioning during idle Mode. Set to program PCA to be gated off during idle. Watchdog Timer Enable 6 WDTE Cleared to disable Watchdog Timer function on PCA Module 4. Set to enable Watchdog Timer function on PCA Module 4. 5 Reserved The value read from this bit is indeterminate. Do not set this bit. Reserved The value read from this bit is indeterminate. Do not set this bit. Reserved The value read from this bit is indeterminate. Do not set this bit. PCA Count Pulse Select CPS1CPS0 0 0 1 CPS0 0 1 1 1 0 1 Selected PCA input Internal clock FCLK PERIPH/6 Internal clock FCLK PERIPH/2 Timer 0 Overflow External clock at ECI/P1.2 pin (max rate = FCLK PERIPH/4) 5 4 3 2 CPS1 1 CPS0 0 ECF 4 - 3 2 CPS1 0 ECF PCA Enable Counter Overflow Interrupt Cleared to disable CF bit in CCON to inhibit an interrupt. Set to enable CF bit in CCON to generate an interrupt. Reset Value = 00XX X000b Not bit addressable The CCON register contains the run control bit for the PCA and the flags for the PCA timer (CF) and each module (Refer to Table 13-2). • Bit CR (CCON.6) must be set by software to run the PCA. The PCA is shut off by clearing this bit. • Bit CF: The CF bit (CCON.7) is set when the PCA counter overflows and an interrupt will be generated if the ECF bit in the CMOD register is set. The CF bit can only be cleared by software. • Bits 0 through 4 are the flags for the modules (bit 0 for module 0, bit 1 for module 1, etc.) and are set by hardware when either a match or a capture occurs. These flags also can only be cleared by software. 37 4235K–8051–05/08 Table 13-2. CCON Register CCON - PCA Counter Control Register (D8h) 7 CF Bit Number 6 CR Bit Mnemonic Description PCA Counter Overflow flag 7 CF Set by hardware when the counter rolls over. CF flags an interrupt if bit ECF in CMOD is set. CF may be set by either hardware or software but can only be cleared by software. PCA Counter Run control bit 6 CR Must be cleared by software to turn the PCA counter off. Set by software to turn the PCA counter on. 5 Reserved The value read from this bit is indeterminate. Do not set this bit. PCA Module 4 interrupt flag 4 CCF4 Must be cleared by software. Set by hardware when a match or capture occurs. PCA Module 3 interrupt flag 3 CCF3 Must be cleared by software. Set by hardware when a match or capture occurs. PCA Module 2 interrupt flag 2 CCF2 Must be cleared by software. Set by hardware when a match or capture occurs. PCA Module 1 interrupt flag 1 CCF1 Must be cleared by software. Set by hardware when a match or capture occurs. PCA Module 0 interrupt flag 0 CCF0 Must be cleared by software. Set by hardware when a match or capture occurs. 5 4 CCF4 3 CCF3 2 CCF2 1 CCF1 0 CCF0 Reset Value = 00X0 0000b Bit addressable The watchdog timer function is implemented in Module 4 (See Figure 13-4). The PCA interrupt system is shown in Figure 13-2. 38 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Figure 13-2. PCA Interrupt System CF PCA Timer/Counter CR CCF4 CCF3 CCF2 CCF1 CCF0 CCON 0xD8 Module 0 Module 1 To Interrupt Priority Decoder Module 2 Module 3 Module 4 CMOD.0 ECF ECCFn CCAPMn.0 IEN0.6 EC IEN0.7 EA PCA Modules: each one of the five compare/capture modules has six possible functions. It can perform: • 16-bit Capture, positive-edge triggered • 16-bit Capture, negative-edge triggered • 16-bit Capture, both positive and negative-edge triggered • 16-bit Software Timer • 16-bit High Speed Output • 8-bit Pulse Width Modulator In addition, Module 4 can be used as a Watchdog Timer. Each module in the PCA has a special function register associated with it. These registers are: CCAPM0 for Module 0, CCAPM1 for Module 1, etc. (See Table 13-3). The registers contain the bits that control the mode that each module will operate in. • The ECCF bit (CCAPMn.0 where n = 0, 1, 2, 3, or 4 depending on the module) enables the CCF flag in the CCON SFR to generate an interrupt when a match or compare occurs in the associated module. • PWM (CCAPMn.1) enables the pulse width modulation mode. • The TOG bit (CCAPMn.2) when set causes the CEX output associated with the module to toggle when there is a match between the PCA counter and the modules capture/compare register. • The match bit MAT (CCAPMn.3) when set will cause the CCFn bit in the CCON register to be set when there is a match between the PCA counter and the modules capture/compare register. • The next two bits CAPN (CCAPMn.4) and CAPP (CCAPMn.5) determine the edge that a capture input will be active on. The CAPN bit enables the negative edge, and the CAPP bit enables the positive edge. If both bits are set both edges will be enabled and a capture will occur for either transition. • The last bit in the register ECOM (CCAPMn.6) when set enables the comparator function. 39 4235K–8051–05/08 Table 13-3 shows the CCAPMn settings for the various PCA functions. Table 13-3. CCAPMn Registers (n = 0-4) CCAPM0 - PCA Module 0 Compare/Capture Control Register (0DAh) CCAPM1 - PCA Module 1 Compare/Capture Control Register (0DBh) CCAPM2 - PCA Module 2 Compare/Capture Control Register (0DCh) CCAPM3 - PCA Module 3 Compare/Capture Control Register (0DDh) CCAPM4 - PCA Module 4 Compare/Capture Control Register (0DEh) 7 Bit Number 7 6 ECOMn Bit Mnemonic Description Reserved The value read from this bit is indeterminate. Do not set this bit. Enable Comparator 6 ECOMn Cleared to disable the comparator function. Set to enable the comparator function. Capture Positive 5 CAPPn Cleared to disable positive edge capture. Set to enable positive edge capture. Capture Negative 4 CAPNn Cleared to disable negative edge capture. Set to enable negative edge capture. Match 3 MATn When MATn = 1, a match of the PCA counter with this module's compare/capture register causes the CCFn bit in CCON to be set, flagging an interrupt. Toggle 2 TOGn When TOGn = 1, a match of the PCA counter with this module's compare/capture register causes the CEXn pin to toggle. Pulse Width Modulation Mode 1 PWMn Cleared to disable the CEXn pin to be used as a pulse width modulated output. Set to enable the CEXn pin to be used as a pulse width modulated output. Enable CCF interrupt 0 CCF0 Cleared to disable compare/capture flag CCFn in the CCON register to generate an interrupt. Set to enable compare/capture flag CCFn in the CCON register to generate an interrupt. 5 CAPPn 4 CAPNn 3 MATn 2 TOGn 1 PWMn 0 ECCFn Reset Value = X000 0000b Not bit addressable 40 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 13-4. ECOMn 0 X PCA Module Modes (CCAPMn Registers) CAPNn 0 0 MATn 0 0 TOGn 0 0 PWMm 0 0 ECCFn 0 X Module Function No Operation 16-bit capture by a positive-edge trigger on CEXn 16-bit capture by a negative trigger on CEXn 16-bit capture by a transition on CEXn 16-bit Software Timer/Compare mode. 16-bit High Speed Output 8-bit PWM Watchdog Timer (module 4 only) CAPPn 0 1 X X 1 1 1 1 0 1 0 0 0 0 1 1 0 0 0 0 0 0 1 1 0 1 0 0 0 1 0 X 0 0 0 0 1 0 X X X X 0 X There are two additional registers associated with each of the PCA modules. They are CCAPnH and CCAPnL and these are the registers that store the 16-bit count when a capture occurs or a compare should occur. When a module is used in the PWM mode these registers are used to control the duty cycle of the output (See Table 13-5 & Table 13-6). Table 13-5. CCAPnH Registers (n = 0 - 4) CCAP0H - PCA Module 0 Compare/Capture Control Register High (0FAh) CCAP1H - PCA Module 1 Compare/Capture Control Register High (0FBh) CCAP2H - PCA Module 2 Compare/Capture Control Register High (0FCh) CCAP3H - PCA Module 3 Compare/Capture Control Register High (0FDh) CCAP4H - PCA Module 4 Compare/Capture Control Register High (0FEh) 7 Bit Number 7-0 6 Bit Mnemonic Description PCA Module n Compare/Capture Control CCAPnH Value 5 4 3 2 1 0 - Reset Value = 0000 0000b Not bit addressable 41 4235K–8051–05/08 Table 13-6. CCAPnL Registers (n = 0 - 4) CCAP0L - PCA Module 0 Compare/Capture Control Register Low (0EAh) CCAP1L - PCA Module 1 Compare/Capture Control Register Low (0EBh) CCAP2L - PCA Module 2 Compare/Capture Control Register Low (0ECh) CCAP3L - PCA Module 3 Compare/Capture Control Register Low (0EDh) CCAP4L - PCA Module 4 Compare/Capture Control Register Low (0EEh) 7 Bit Number 7-0 6 Bit Mnemonic Description PCA Module n Compare/Capture Control CCAPnL Value 5 4 3 2 1 0 - Reset Value = 0000 0000b Not bit addressable Table 13-7. CH Register CH - PCA Counter Register High (0F9h) 7 Bit Number 7-0 6 Bit Mnemonic Description PCA counter CH Value 5 4 3 2 1 0 - Reset Value = 0000 0000b Not bit addressable Table 13-8. CL Register CL - PCA Counter Register Low (0E9h) 7 Bit Number 7-0 6 Bit Mnemonic Description PCA Counter CL Value 5 4 3 2 1 0 - Reset Value = 0000 0000b Not bit addressable 42 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 13.1 PCA Capture Mode To use one of the PCA modules in the capture mode either one or both of the CCAPM bits CAPN and CAPP for that module must be set. The external CEX input for the module (on port 1) is sampled for a transition. When a valid transition occurs the PCA hardware loads the value of the PCA counter registers (CH and CL) into the module's capture registers (CCAPnL and CCAPnH). If the CCFn bit for the module in the CCON SFR and the ECCFn bit in the CCAPMn SFR are set then an interrupt will be generated (Refer to Figure 13-3). Figure 13-3. PCA Capture Mode CF CR CCF4 CCF3 CCF2 CCF1 CCF0 CCON 0xD8 PCA IT PCA Counter/Timer Cex.n Capture CH CL CCAPnH CCAPnL ECOMn CAPPn CAPNn MATn TOGn PWMn ECCFn CCAPMn, n= 0 to 4 0xDA to 0xDE 13.2 16-bit Software Timer/ Compare Mode The PCA modules can be used as software timers by setting both the ECOM and MAT bits in the modules CCAPMn register. The PCA timer will be compared to the module's capture registers and when a match occurs an interrupt will occur if the CCFn (CCON SFR) and the ECCFn (CCAPMn SFR) bits for the module are both set (See Figure 13-4). 43 4235K–8051–05/08 Figure 13-4. PCA Compare Mode and PCA Watchdog Timer CCON CF Write to CCAPnL Write to CCAPnH 1 0 Enable 16 bit comparator RESET * Reset PCA IT CCAPnH CCAPnL Match CR CCF4 CCF3 CCF2 CCF1 CCF0 0xD8 CH CL PCA counter/timer ECOMn CAPPn CAPNn MATn TOGn PWMn ECCFn CCAPMn, n = 0 to 4 0xDA to 0xDE CIDL WDTE CPS1 CPS0 ECF CMOD 0xD9 Before enabling ECOM bit, CCAPnL and CCAPnH should be set with a non zero value, otherwise an unwanted match could happen. Writing to CCAPnH will set the ECOM bit. Once ECOM is set, writing CCAPnL will clear ECOM so that an unwanted match doesn’t occur while modifying the compare value. Writing to CCAPnH will set ECOM. For this reason, user software should write CCAPnL first, and then CCAPnH. Of course, the ECOM bit can still be controlled by accessing to CCAPMn register. 13.3 High Speed Output Mode In this mode the CEX output (on port 1) associated with the PCA module will toggle each time a match occurs between the PCA counter and the modules capture registers. To activate this mode the TOG, MAT, and ECOM bits in the module's CCAPMn SFR must be set (See Figure 13-5). A prior write must be done to CCAPnL and CCAPnH before writing the ECOMn bit. 44 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Figure 13-5. PCA High Speed Output Mode CCON CF CR CCF4 CCF3 CCF2 CCF1 CCF0 0xD8 Write to CCA PnL Reset PCA IT Write to CCAPnH 0 CCAPnH Enable 16 bit comparator CCAPnL Match 1 CH CL CEXn PCA counter/timer CCAPMn, n = 0 to 4 0xDA to 0xDE ECO Mn CAPPn CAPNn MATn TOGn PWMn ECCFn Before enabling ECOM bit, CCAPnL and CCAPnH should be set with a non zero value, otherwise an unwanted match could happen. Once ECOM is set, writing CCAPnL will clear ECOM so that an unwanted match doesn’t occur while modifying the compare value. Writing to CCAPnH will set ECOM. For this reason, user software should write CCAPnL first, and then CCAPnH. Of course, the ECOM bit can still be controlled by accessing to CCAPMn register. 13.4 Pulse Width Modulator Mode All of the PCA modules can be used as PWM outputs. Figure 13-6 shows the PWM function. The frequency of the output depends on the source for the PCA timer. All of the modules will have the same frequency of output because they all share the PCA timer. The duty cycle of each module is independently variable using the modules capture register CCAPLn. When the value of the PCA CL SFR is less than the value in the modules CCAPLn SFR the output will be low, when it is equal to or greater than the output will be high. When CL overflows from FF to 00, CCAPLn is reloaded with the value in CCAPHn. This allows updating the PWM without glitches. The PWM and ECOM bits in the module's CCAPMn register must be set to enable the PWM mode. 45 4235K–8051–05/08 Figure 13-6. PCA PWM Mode CCAPnH Overflow CCAPnL “0” Enable 8-bit Comparator “1” CL PCA Counter/Timer CEXn ECOMn CAPPn CAPNn MATn TOGn PWMn ECCFn CCAPMn, n= 0 to 4 0xDA to 0xDE 13.5 PCA Watchdog Timer An on-board watchdog timer is available with the PCA to improve the reliability of the system without increasing chip count. Watchdog timers are useful for systems that are susceptible to noise, power glitches, or electrostatic discharge. Module 4 is the only PCA module that can be programmed as a watchdog. However, this module can still be used for other modes if the watchdog is not needed. Figure 13-4 shows a diagram of how the watchdog works. The user pre-loads a 16-bit value in the compare registers. Just like the other compare modes, this 16-bit value is compared to the PCA timer value. If a match is allowed to occur, an internal reset will be generated. This will not cause the RST pin to be driven high. In order to hold off the reset, the user has three options: 1. Periodically change the compare value so it will never match the PCA timer. 2. Periodically change the PCA timer value so it will never match the compare values. 3. Disable the watchdog by clearing the WDTE bit before a match occurs and then reenable it. 46 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 The first two options are more reliable because the watchdog timer is never disabled as in option #3. If the program counter ever goes astray, a match will eventually occur and cause an internal reset. The second option is also not recommended if other PCA modules are being used. Remember, the PCA timer is the time base for all modules; changing the time base for other modules would not be a good idea. Thus, in most applications the first solution is the best option. This watchdog timer won’t generate a reset out on the reset pin. 47 4235K–8051–05/08 14. Serial I/O Port The serial I/O port in the AT89C51RD2/ED2 is compatible with the serial I/O port in the 80C52. It provides both synchronous and asynchronous communication modes. It operates as a Universal Asynchronous Receiver and Transmitter (UART) in three full-duplex modes (Modes 1, 2 and 3). Asynchronous transmission and reception can occur simultaneously and at different baud rates Serial I/O port includes the following enhancements: • Framing error detection • Automatic address recognition 14.1 Framing Error Detection Framing bit error detection is provided for the three asynchronous modes (modes 1, 2 and 3). To enable the framing bit error detection feature, set SMOD0 bit in PCON register (See Figure 141). Figure 14-1. Framing Error Block Diagram SM0/FE SM1 SM2 REN TB8 RB8 TI RI SCON (98h) Set FE bit if stop bit is 0 (framing error) (SMOD0 = 1) SM0 to UART mode control (SMOD0 = 0) SMOD1SMOD0 POF GF1 GF0 PD IDL PCON (87h) To UART framing error control When this feature is enabled, the receiver checks each incoming data frame for a valid stop bit. An invalid stop bit may result from noise on the serial lines or from simultaneous transmission by two CPUs. If a valid stop bit is not found, the Framing Error bit (FE) in SCON register (See Table 14-4.) bit is set. Software may examine FE bit after each reception to check for data errors. Once set, only software or a reset can clear FE bit. Subsequently received frames with valid stop bits cannot clear FE bit. When FE feature is enabled, RI rises on stop bit instead of the last data bit (See Figure 14-2. and Figure 14-3.). Figure 14-2. UART Timings in Mode 1 RXD Start bit RI SMOD0=X FE SMOD0=1 D0 D1 D2 D3 D4 D5 D6 D7 Stop bit Data byte 48 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Figure 14-3. UART Timings in Modes 2 and 3 RXD Start bit RI SMOD0=0 RI SMOD0=1 FE SMOD0=1 D0 D1 D2 D3 D4 D5 D6 D7 D8 Ninth Stop bit bit Data byte 14.2 Automatic Address Recognition The automatic address recognition feature is enabled when the multiprocessor communication feature is enabled (SM2 bit in SCON register is set). Implemented in hardware, automatic address recognition enhances the multiprocessor communication feature by allowing the serial port to examine the address of each incoming command frame. Only when the serial port recognizes its own address, the receiver sets RI bit in SCON register to generate an interrupt. This ensures that the CPU is not interrupted by command frames addressed to other devices. If desired, the user may enable the automatic address recognition feature in mode 1.In this configuration, the stop bit takes the place of the ninth data bit. Bit RI is set only when the received command frame address matches the device’s address and is terminated by a valid stop bit. To support automatic address recognition, a device is identified by a given address and a broadcast address. Note: The multiprocessor communication and automatic address recognition features cannot be enabled in mode 0 (i. e. setting SM2 bit in SCON register in mode 0 has no effect). 14.2.1 Given Address Each device has an individual address that is specified in SADDR register; the SADEN register is a mask byte that contains don’t-care bits (defined by zeros) to form the device’s given address. The don’t-care bits provide the flexibility to address one or more slaves at a time. The following example illustrates how a given address is formed. To address a device by its individual address, the SADEN mask byte must be 1111 1111b. For example: SADDR0101 0110b SADEN1111 1100b Given0101 01XXb The following is an example of how to use given addresses to address different slaves: Slave A:SADDR1111 0001b SADEN1111 1010b Given1111 0X0Xb Slave B:SADDR1111 0011b SADEN1111 1001b Given1111 0XX1b 49 4235K–8051–05/08 Slave C:SADDR1111 0010b SADEN1111 1101b Given1111 00X1b The SADEN byte is selected so that each slave may be addressed separately. For slave A, bit 0 (the LSB) is a don’t-care bit; for slaves B and C, bit 0 is a 1.To communicate with slave A only, the master must send an address where bit 0 is clear (e. g. 1111 0000b). For slave A, bit 1 is a 1; for slaves B and C, bit 1 is a don’t care bit. To communicate with slaves B and C, but not slave A, the master must send an address with bits 0 and 1 both set (e. g. 1111 0011b). To communicate with slaves A, B and C, the master must send an address with bit 0 set, bit 1 clear, and bit 2 clear (e. g. 1111 0001b). 14.2.2 Broadcast Address A broadcast address is formed from the logical OR of the SADDR and SADEN registers with zeros defined as don’t-care bits, e. g. : SADDR0101 0110b SADEN1111 1100b Broadcast =SADDR OR SADEN1111 111Xb The use of don’t-care bits provides flexibility in defining the broadcast address, however in most applications, a broadcast address is FFh. The following is an example of using broadcast addresses: Slave A:SADDR1111 0001b SADEN1111 1010b Broadcast1111 1X11b, Slave B:SADDR1111 0011b SADEN1111 1001b Broadcast1111 1X11B, Slave C:SADDR=1111 0011b SADEN1111 1101b Broadcast1111 1111b For slaves A and B, bit 2 is a don’t care bit; for slave C, bit 2 is set. To communicate with all of the slaves, the master must send an address FFh. To communicate with slaves A and B, but not slave C, the master can send and address FBh. 14.2.3 Reset Addresses On reset, the SADDR and SADEN registers are initialized to 00h, i. e. the given and broadcast addresses are XXXX XXXXb (all don’t-care bits). This ensures that the serial port will reply to any address, and so, that it is backwards compatible with the 80C51 microcontrollers that do not support automatic address recognition. 50 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 14.3 Registers Table 14-1. SADEN Register SADEN - Slave Address Mask Register (B9h) 7 6 5 4 3 2 1 0 Reset Value = 0000 0000b Not bit addressable Table 14-2. SADDR Register SADDR - Slave Address Register (A9h) 7 6 5 4 3 2 1 0 Reset Value = 0000 0000b Not bit addressable 14.4 Baud Rate Selection for UART for Mode 1 and 3 The Baud Rate Generator for transmit and receive clocks can be selected separately via the T2CON and BDRCON registers. Figure 14-4. Baud Rate Selection TIMER1 TIMER2 0 1 RCLK INT_BRG RBCK TIMER_BRG_RX 0 1 / 16 Rx Clock TIMER1 TIMER2 0 1 TCLK TIMER_BRG_TX 0 1 / 16 Tx Clock INT_BRG TBCK 51 4235K–8051–05/08 Table 14-3. TCLK (T2CON) 0 1 0 1 X X 0 1 X Baud Rate Selection Table UART RCLK (T2CON) 0 0 1 1 0 1 X X X TBCK (BDRCON) 0 0 0 0 1 1 0 0 1 RBCK (BDRCON) 0 0 0 0 0 0 1 1 1 Clock Source UART Tx Timer 1 Timer 2 Timer 1 Timer 2 INT_BRG INT_BRG Timer 1 Timer 2 INT_BRG Clock Source UART Rx Timer 1 Timer 1 Timer 2 Timer 2 Timer 1 Timer 2 INT_BRG INT_BRG INT_BRG 14.4.1 Internal Baud Rate Generator (BRG) When the internal Baud Rate Generator is used, the Baud Rates are determined by the BRG overflow depending on the BRL reload value, the value of SPD bit (Speed Mode) in BDRCON register and the value of the SMOD1 bit in PCON register. Figure 14-5. Internal Baud Rate FClk Periph ÷6 0 1 BRG (8 bits) BRR BDRCON.4 Overflow ÷2 0 INT_BRG 1 SPD BDRCON.1 SMOD1 PCON.7 BRL (8 bits) • The baud rate for UART is token by formula: Baud_Rate = 6 (1-SPD) 2SMOD1 ⋅ FPER ⋅ 32 ⋅ (256 -BRL) 2SMOD1 ⋅ FPER ⋅ 32 ⋅ Baud_Rate BRL = 256 - 6 (1-SPD) 52 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 14-4. SCON Register SCON - Serial Control Register (98h) 7 FE/SM0 Bit Number 6 SM1 Bit Mnemonic Description Framing Error bit (SMOD0=1) FE 7 SM0 Clear to reset the error state, not cleared by a valid stop bit. Set by hardware when an invalid stop bit is detected. SMOD0 must be set to enable access to the FE bit. Serial port Mode bit 0 Refer to SM1 for serial port mode selection. SMOD0 must be cleared to enable access to the SM0 bit. Serial port Mode bit 1 SM0SM1Mode Baud Rate 0 0 Shift Register FXTAL/12 (or FXTAL /6 in mode X2) 0 1 8-bit UART Variable 1 0 9-bit UARTFXTAL/64 or FXTAL/32 1 1 9-bit UARTVariable Serial port Mode 2 bit / Multiprocessor Communication Enable bit 5 SM2 Clear to disable multiprocessor communication feature. Set to enable multiprocessor communication feature in mode 2 and 3, and eventually mode 1.This bit should be cleared in mode 0. Reception Enable bit Clear to disable serial reception. Set to enable serial reception. Transmitter Bit 8 / Ninth bit to transmit in modes 2 and 3 3 TB8 Clear to transmit a logic 0 in the 9th bit. Set to transmit a logic 1 in the 9th bit. Receiver Bit 8 / Ninth bit received in modes 2 and 3 Cleared by hardware if 9th bit received is a logic 0. Set by hardware if 9th bit received is a logic 1. In mode 1, if SM2 = 0, RB8 is the received stop bit. In mode 0 RB8 is not used. Transmit Interrupt flag Clear to acknowledge interrupt. 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. Receive Interrupt flag Clear to acknowledge interrupt. Set by hardware at the end of the 8th bit time in mode 0, see Figure 14-2. and Figure 14-3. in the other modes. 5 SM2 4 REN 3 TB8 2 RB8 1 TI 0 RI 6 SM1 4 REN 2 RB8 1 TI 0 RI Reset Value = 0000 0000b Bit addressable 53 4235K–8051–05/08 Table 14-5. Baud Rates Example of Computed Value When X2=1, SMOD1=1, SPD=1 FOSC = 16. 384 MHz BRL Error (%) 1.23 1.23 1.23 1.23 0.63 0.31 1.23 BRL 243 230 217 204 178 100 FOSC = 24MHz Error (%) 0.16 0.16 0.16 0.16 0.16 0.16 - 115200 57600 38400 28800 19200 9600 4800 247 238 229 220 203 149 43 Table 14-6. Baud Rates Example of Computed Value When X2=0, SMOD1=0, SPD=0 FOSC = 16. 384 MHz BRL Error (%) 1.23 1.23 1.23 0.16 BRL 243 230 202 152 FOSC = 24MHz Error (%) 0.16 0.16 3.55 0.16 4800 2400 1200 600 247 238 220 185 The baud rate generator can be used for mode 1 or 3 (refer to Figure 14-4.), but also for mode 0 for UART, thanks to the bit SRC located in BDRCON register (Table 14-13.) 14.5 UART Registers Table 14-7. SADEN Register SADEN - Slave Address Mask Register for UART (B9h) 7 6 5 4 3 2 1 0 Reset Value = 0000 0000b Table 14-8. SADDR Register SADDR - Slave Address Register for UART (A9h) 7 6 5 4 3 2 1 0 Reset Value = 0000 0000b 54 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 14-9. SBUF Register SBUF - Serial Buffer Register for UART (99h) 7 6 5 4 3 2 1 0 Reset Value = XXXX XXXXb Table 14-10. BRL Register BRL - Baud Rate Reload Register for the internal baud rate generator, UART (9Ah) 7 6 5 4 3 2 1 0 Reset Value = 0000 0000b 55 4235K–8051–05/08 Table 14-11. T2CON Register T2CON - Timer 2 Control Register (C8h) 7 TF2 Bit Number 6 EXF2 Bit Mnemonic Description Timer 2 overflow Flag Must be cleared by software. Set by hardware on timer 2 overflow, if RCLK = 0 and TCLK = 0. Timer 2 External Flag Set when a capture or a reload is caused by a negative transition on T2EX pin if EXEN2=1. When set, causes the CPU to vector to timer 2 interrupt routine when timer 2 interrupt is enabled. Must be cleared by software. EXF2 doesn’t cause an interrupt in Up/down counter mode (DCEN = 1) Receive Clock bit for UART Cleared to use timer 1 overflow as receive clock for serial port in mode 1 or 3. Set to use timer 2 overflow as receive clock for serial port in mode 1 or 3. Transmit Clock bit for UART Cleared to use timer 1 overflow as transmit clock for serial port in mode 1 or 3. Set to use timer 2 overflow as transmit clock for serial port in mode 1 or 3. Timer 2 External Enable bit Cleared to ignore events on T2EX pin for timer 2 operation. Set to cause a capture or reload when a negative transition on T2EX pin is detected, if timer 2 is not used to clock the serial port. Timer 2 Run control bit Cleared to turn off timer 2. Set to turn on timer 2. Timer/Counter 2 select bit Cleared for timer operation (input from internal clock system: FCLK PERIPH). Set for counter operation (input from T2 input pin, falling edge trigger). Must be 0 for clock out mode. Timer 2 Capture/Reload bit If RCLK=1 or TCLK=1, CP/RL2# is ignored and timer is forced to auto-reload on timer 2 overflow. Cleared to auto-reload on timer 2 overflows or negative transitions on T2EX pin if EXEN2=1. Set to capture on negative transitions on T2EX pin if EXEN2=1. 5 RCLK 4 TCLK 3 EXEN2 2 TR2 1 C/T2# 0 CP/RL2# 7 TF2 6 EXF2 5 RCLK 4 TCLK 3 EXEN2 2 TR2 1 C/T2# 0 CP/RL2# Reset Value = 0000 0000b Bit addressable 56 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 14-12. PCON Register PCON - Power Control Register (87h) 7 SMOD1 Bit Number 7 6 SMOD0 Bit Mnemonic SMOD1 Description Serial port Mode bit 1 for UART Set to select double baud rate in mode 1, 2 or 3. Serial port Mode bit 0 for UART 6 SMOD0 Cleared to select SM0 bit in SCON register. Set to select FE bit in SCON register. Reserved The value read from this bit is indeterminate. Do not set this bit. Power-Off Flag Cleared to recognize next reset type. Set by hardware when VCC rises from 0 to its nominal voltage. Can also be set by software. General purpose Flag Cleared by user for general purpose usage. Set by user for general purpose usage. General purpose Flag Cleared by user for general purpose usage. Set by user for general purpose usage. Power-Down mode bit Cleared by hardware when reset occurs. Set to enter power-down mode. Idle mode bit Cleared by hardware when interrupt or reset occurs. Set to enter idle mode. 5 4 POF 3 GF1 2 GF0 1 PD 0 IDL 5 - 4 POF 3 GF1 2 GF0 1 PD 0 IDL Reset Value = 00X1 0000b Not bit addressable Power-off flag reset value will be 1 only after a power on (cold reset). A warm reset doesn’t affect the value of this bit. 57 4235K–8051–05/08 Table 14-13. BDRCON Register BDRCON - Baud Rate Control Register (9Bh) 7 Bit Number 7 6 Bit Mnemonic 5 4 BRR 3 TBCK 2 RBCK 1 SPD 0 SRC Description Reserved The value read from this bit is indeterminate. Do not set this bit Reserved The value read from this bit is indeterminate. Do not set this bit Reserved The value read from this bit is indeterminate. Do not set this bit. Baud Rate Run Control bit Cleared to stop the internal Baud Rate Generator. Set to start the internal Baud Rate Generator. Transmission Baud rate Generator Selection bit for UART Cleared to select Timer 1 or Timer 2 for the Baud Rate Generator. Set to select internal Baud Rate Generator. Reception Baud Rate Generator Selection bit for UART Cleared to select Timer 1 or Timer 2 for the Baud Rate Generator. Set to select internal Baud Rate Generator. Baud Rate Speed Control bit for UART Cleared to select the SLOW Baud Rate Generator. Set to select the FAST Baud Rate Generator. Baud Rate Source select bit in Mode 0 for UART 6 - 5 - 4 BRR 3 TBCK 2 RBCK 1 SPD 0 SRC Cleared to select FOSC/12 as the Baud Rate Generator (FCLK PERIPH/6 in X2 mode). Set to select the internal Baud Rate Generator for UARTs in mode 0. Reset Value = XXX0 0000b Not bit addressable 58 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 15. Keyboard Interface The AT89C51RD2/ED2 implements a keyboard interface allowing the connection of a 8 x n matrix keyboard. It is based on 8 inputs with programmable interrupt capability on both high or low level. These inputs are available as alternate function of P1 and allow to exit from idle and power-down modes. The keyboard interfaces with the C51 core through 3 special function registers: KBLS, the Keyboard Level Selection register (Table 15-3), KBE, the Keyboard interrupt Enable register (Table 15-2), and KBF, the Keyboard Flag register (Table 15-1). 15.0.1 Interrupt The keyboard inputs are considered as 8 independent interrupt sources sharing the same interrupt vector. An interrupt enable bit (KBD in IE1) allows global enable or disable of the keyboard interrupt (see Figure 15-1). As detailed in Figure 15-2 each keyboard input has the capability to detect a programmable level according to KBLS. x bit value. Level detection is then reported in interrupt flags KBF.x that can be masked by software using KBE. x bits. This structure allow keyboard arrangement from 1 by n to 8 by n matrix and allows usage of P1 inputs for other purpose. Figure 15-1. Keyboard Interface Block Diagram Vcc 0 P1:x 1 Internal Pullup KBF.x KBE.x KBLS.x Figure 15-2. Keyboard Input Circuitry P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 P1.6 P1.7 Input Circuitry Input Circuitry Input Circuitry Input Circuitry KBDIT Input Circuitry Input Circuitry Input Circuitry Input Circuitry KBD IE1 Keyboard Interface Interrupt Request 15.0.2 Power Reduction Mode P1 inputs allow exit from idle and power-down modes as detailed in Section “Power Management”, page 80. 59 4235K–8051–05/08 15.1 Registers Table 15-1. KBF Register KBF-Keyboard Flag Register (9Eh) 7 KBF7 6 KBF6 Bit Mnemonic 5 KBF5 4 KBF4 3 KBF3 2 KBF2 1 KBF1 0 KBF0 Bit Number Description Keyboard line 7 flag Set by hardware when the Port line 7 detects a programmed level. It generates a Keyboard interrupt request if the KBKBIE.7 bit in KBIE register is set. Must be cleared by software. Keyboard line 6 flag Set by hardware when the Port line 6 detects a programmed level. It generates a Keyboard interrupt request if the KBIE.6 bit in KBIE register is set. Must be cleared by software. Keyboard line 5 flag Set by hardware when the Port line 5 detects a programmed level. It generates a Keyboard interrupt request if the KBIE.5 bit in KBIE register is set. Must be cleared by software. Keyboard line 4 flag Set by hardware when the Port line 4 detects a programmed level. It generates a Keyboard interrupt request if the KBIE.4 bit in KBIE register is set. Must be cleared by software. Keyboard line 3 flag Set by hardware when the Port line 3 detects a programmed level. It generates a Keyboard interrupt request if the KBIE.3 bit in KBIE register is set. Must be cleared by software. Keyboard line 2 flag Set by hardware when the Port line 2 detects a programmed level. It generates a Keyboard interrupt request if the KBIE.2 bit in KBIE register is set. Must be cleared by software. Keyboard line 1 flag Set by hardware when the Port line 1 detects a programmed level. It generates a Keyboard interrupt request if the KBIE.1 bit in KBIE register is set. Must be cleared by software. Keyboard line 0 flag Set by hardware when the Port line 0 detects a programmed level. It generates a Keyboard interrupt request if the KBIE.0 bit in KBIE register is set. Must be cleared by software. 7 KBF7 6 KBF6 5 KBF5 4 KBF4 3 KBF3 2 KBF2 1 KBF1 0 KBF0 Reset Value = 0000 0000b This register is read only access, all flags are automatically cleared by reading the register. 60 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 15-2. KBE Register KBE-Keyboard Input Enable Register (9Dh) 7 KBE7 Bit Number 6 KBE6 Bit Mnemonic 5 KBE5 4 KBE4 3 KBE3 2 KBE2 1 KBE1 0 KBE0 Description Keyboard line 7 Enable bit Cleared to enable standard I/O pin. Set to enable KBF.7 bit in KBF register to generate an interrupt request. Keyboard line 6 Enable bit Cleared to enable standard I/O pin. Set to enable KBF.6 bit in KBF register to generate an interrupt request. Keyboard line 5 Enable bit Cleared to enable standard I/O pin. Set to enable KBF.5 bit in KBF register to generate an interrupt request. Keyboard line 4 Enable bit Cleared to enable standard I/O pin. Set to enable KBF.4 bit in KBF register to generate an interrupt request. Keyboard line 3 Enable bit Cleared to enable standard I/O pin. Set to enable KBF.3 bit in KBF register to generate an interrupt request. Keyboard line 2 Enable bit Cleared to enable standard I/O pin. Set to enable KBF.2 bit in KBF register to generate an interrupt request. Keyboard line 1 Enable bit Cleared to enable standard I/O pin. Set to enable KBF.1 bit in KBF register to generate an interrupt request. Keyboard line 0 Enable bit Cleared to enable standard I/O pin. Set to enable KBF.0 bit in KBF register to generate an interrupt request. 7 KBE7 6 KBE6 5 KBE5 4 KBE4 3 KBE3 2 KBE2 1 KBE1 0 KBE0 Reset Value = 0000 0000b 61 4235K–8051–05/08 Table 15-3. KBLS Register KBLS-Keyboard Level Selector Register (9Ch) 7 KBLS7 6 KBLS6 Bit Mnemonic 5 KBLS5 4 KBLS4 3 KBLS3 2 KBLS2 1 KBLS1 0 KBLS0 Bit Number Description Keyboard line 7 Level Selection bit Cleared to enable a low level detection on Port line 7. Set to enable a high level detection on Port line 7. Keyboard line 6 Level Selection bit Cleared to enable a low level detection on Port line 6. Set to enable a high level detection on Port line 6. Keyboard line 5 Level Selection bit Cleared to enable a low level detection on Port line 5. Set to enable a high level detection on Port line 5. Keyboard line 4 Level Selection bit Cleared to enable a low level detection on Port line 4. Set to enable a high level detection on Port line 4. Keyboard line 3 Level Selection bit Cleared to enable a low level detection on Port line 3. Set to enable a high level detection on Port line 3. Keyboard line 2 Level Selection bit Cleared to enable a low level detection on Port line 2. Set to enable a high level detection on Port line 2. Keyboard line 1 Level Selection bit Cleared to enable a low level detection on Port line 1. Set to enable a high level detection on Port line 1. Keyboard line 0 Level Selection bit Cleared to enable a low level detection on Port line 0. Set to enable a high level detection on Port line 0. 7 KBLS7 6 KBLS6 5 KBLS5 4 KBLS4 3 KBLS3 2 KBLS2 1 KBLS1 0 KBLS0 Reset Value = 0000 0000b 62 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 16. Serial Port Interface (SPI) The Serial Peripheral Interface Module (SPI) allows full-duplex, synchronous, serial communication between the MCU and peripheral devices, including other MCUs. 16.1 Features Features of the SPI Module include the following: • Full-duplex, three-wire synchronous transfers • Master or Slave operation • Eight programmable Master clock rates • Serial clock with programmable polarity and phase • Master Mode fault error flag with MCU interrupt capability • Write collision flag protection 16.2 Signal Description Figure 16-1 shows a typical SPI bus configuration using one Master controller and many Slave peripherals. The bus is made of three wires connecting all the devices. Figure 16-1. SPI Master/Slaves Interconnection MISO MOSI SCK SS Slave 1 MISO MOSI SCK SS VDD Master 0 1 2 3 PORT MISO MOSI SCK SS Slave 4 Slave 3 MISO MOSI SCK SS Slave 2 The Master device selects the individual Slave devices by using four pins of a parallel port to control the four SS pins of the Slave devices. 16.2.1 Master Output Slave Input (MOSI) This 1-bit signal is directly connected between the Master Device and a Slave Device. The MOSI line is used to transfer data in series from the Master to the Slave. Therefore, it is an output signal from the Master, and an input signal to a Slave. A Byte (8-bit word) is transmitted most significant bit (MSB) first, least significant bit (LSB) last. Master Input Slave Output (MISO) This 1-bit signal is directly connected between the Slave Device and a Master Device. The MISO line is used to transfer data in series from the Slave to the Master. Therefore, it is an output signal from the Slave, and an input signal to the Master. A Byte (8-bit word) is transmitted most significant bit (MSB) first, least significant bit (LSB) last. 16.2.2 MISO MOSI SCK SS 63 4235K–8051–05/08 16.2.3 SPI Serial Clock (SCK) This signal is used to synchronize the data movement both in and out of the devices through their MOSI and MISO lines. It is driven by the Master for eight clock cycles which allows to exchange one Byte on the serial lines. Slave Select (SS) Each Slave peripheral is selected by one Slave Select pin (SS). This signal must stay low for any message for a Slave. It is obvious that only one Master (SS high level) can drive the network. The Master may select each Slave device by software through port pins (Figure 16-2). To prevent bus conflicts on the MISO line, only one slave should be selected at a time by the Master for a transmission. In a Master configuration, the SS line can be used in conjunction with the MODF flag in the SPI Status register (SPSTA) to prevent multiple masters from driving MOSI and SCK (see Error conditions). A high level on the SS pin puts the MISO line of a Slave SPI in a high-impedance state. The SS pin could be used as a general-purpose if the following conditions are met: • The device is configured as a Master and the SSDIS control bit in SPCON is set. This kind of configuration can be found when only one Master is driving the network and there is no way that the SS pin could be pulled low. Therefore, the MODF flag in the SPSTA will never be set(1). • The Device is configured as a Slave with CPHA and SSDIS control bits set(2). This kind of configuration can happen when the system comprises one Master and one Slave only. Therefore, the device should always be selected and there is no reason that the Master uses the SS pin to select the communicating Slave device. Note: 1. Clearing SSDIS control bit does not clear MODF. 2. Special care should be taken not to set SSDIS control bit when CPHA = ’0’ because in this mode, the SS is used to start the transmission. 16.2.4 16.2.5 Baud Rate In Master mode, the baud rate can be selected from a baud rate generator which is controlled by three bits in the SPCON register: SPR2, SPR1 and SPR0.The Master clock is selected from one of seven clock rates resulting from the division of the internal clock by 2, 4, 8, 16, 32, 64 or 128. Table 16-1 gives the different clock rates selected by SPR2:SPR1:SPR0. Table 16-1. SPR2 0 0 0 0 1 1 1 1 SPI Master Baud Rate Selection SPR1 0 0 1 1 0 0 1 1 SPR0 0 1 0 1 0 1 0 1 Clock Rate FCLK PERIPH /2 FCLK PERIPH /4 FCLK PERIPH/8 FCLK PERIPH /16 FCLK PERIPH /32 FCLK PERIPH /64 FCLK PERIPH /128 Don’t Use Baud Rate Divisor (BD) 2 4 8 16 32 64 128 No BRG 64 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 16.3 Functional Description Figure 16-2 shows a detailed structure of the SPI Module. Figure 16-2. SPI Module Block Diagram Internal Bus SPDAT FCLK PERIPH Shift Register 7 6 5 4 3 2 1 0 Clock Divider /4 /8 /16 /32 /64 /128 Receive Data Register Pin Control Logic MOSI MISO Clock Logic Clock Select M S SCK SS SPR2 SPEN SSDIS MSTR CPOL CPHA SPR1 SPR0 SPCON SPI Control 8-bit bus 1-bit signal SPI Interrupt Request SPSTA SPIF WCOL MODF - 16.3.1 Operating Modes The Serial Peripheral Interface can be configured in one of the two modes: Master mode or Slave mode. The configuration and initialization of the SPI Module is made through one register: • The Serial Peripheral Control register (SPCON) Once the SPI is configured, the data exchange is made using: • SPCON • The Serial Peripheral STAtus register (SPSTA) • The Serial Peripheral DATa register (SPDAT) During an SPI transmission, data is simultaneously transmitted (shifted out serially) and received (shifted in serially). A serial clock line (SCK) synchronizes shifting and sampling on the two serial data lines (MOSI and MISO). A Slave Select line (SS) allows individual selection of a Slave SPI device; Slave devices that are not selected do not interfere with SPI bus activities. When the Master device transmits data to the Slave device via the MOSI line, the Slave device responds by sending data to the Master device via the MISO line. This implies full-duplex transmission with both data out and data in synchronized with the same clock (Figure 16-3). 65 4235K–8051–05/08 Figure 16-3. Full-Duplex Master-Slave Interconnection MISO MOSI SPI Clock Generator SCK SS VDD MISO MOSI SCK SS VSS 8-bit Shift register 8-bit Shift register Master MCU Slave MCU 16.3.1.1 Master Mode The SPI operates in Master mode when the Master bit, MSTR (1), in the SPCON register is set. Only one Master SPI device can initiate transmissions. Software begins the transmission from a Master SPI Module by writing to the Serial Peripheral Data Register (SPDAT). If the shift register is empty, the Byte is immediately transferred to the shift register. The Byte begins shifting out on MOSI pin under the control of the serial clock, SCK. Simultaneously, another Byte shifts in from the Slave on the Master’s MISO pin. The transmission ends when the Serial Peripheral transfer data flag, SPIF, in SPSTA becomes set. At the same time that SPIF becomes set, the received Byte from the Slave is transferred to the receive data register in SPDAT. Software clears SPIF by reading the Serial Peripheral Status register (SPSTA) with the SPIF bit set, and then reading the SPDAT. Slave Mode The SPI operates in Slave mode when the Master bit, MSTR ( 2) , in the SPCON register is cleared. Before a data transmission occurs, the Slave Select pin, SS, of the Slave device must be set to ’0’. SS must remain low until the transmission is complete. In a Slave SPI Module, data enters the shift register under the control of the SCK from the Master SPI Module. After a Byte enters the shift register, it is immediately transferred to the receive data register in SPDAT, and the SPIF bit is set. To prevent an overflow condition, Slave software must then read the SPDAT before another Byte enters the shift register (3). A Slave SPI must complete the write to the SPDAT (shift register) at least one bus cycle before the Master SPI starts a transmission. If the write to the data register is late, the SPI transmits the data already in the shift register from the previous transmission. The maximum SCK frequency allowed in slave mode is FCLK PERIPH /4. 16.3.1.2 16.3.2 Transmission Formats Software can select any of four combinations of serial clock (SCK) phase and polarity using two bits in the SPCON: the Clock Polarity (CPOL (4)) and the Clock Phase (CPHA4). CPOL defines the default SCK line level in idle state. It has no significant effect on the transmission format. CPHA defines the edges on which the input data are sampled and the edges on which the output data are shifted (Figure 16-4 and Figure 16-5). The clock phase and polarity should be identical for the Master SPI device and the communicating Slave device. 1. 2. 3. 4. The SPI Module should be configured as a Master before it is enabled (SPEN set). Also, the Master SPI should be configured before the Slave SPI. The SPI Module should be configured as a Slave before it is enabled (SPEN set). The maximum frequency of the SCK for an SPI configured as a Slave is the bus clock speed. Before writing to the CPOL and CPHA bits, the SPI should be disabled (SPEN = ’0’). 66 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Figure 16-4. Data Transmission Format (CPHA = 0) SCK Cycle Number SPEN (Internal) 1 2 3 4 5 6 7 8 SCK (CPOL = 0) SCK (CPOL = 1) MOSI (from Master) MISO (from Slave) SS (to Slave) Capture Point MSB MSB bit6 bit6 bit5 bit5 bit4 bit4 bit3 bit3 bit2 bit2 bit1 bit1 LSB LSB Figure 16-5. Data Transmission Format (CPHA = 1) SCK Cycle Number SPEN (Internal) SCK (CPOL = 0) SCK (CPOL = 1) MOSI (from Master) MISO (from Slave) SS (to Slave) Capture Point MSB MSB bit6 bit6 bit5 bit5 bit4 bit4 bit3 bit3 bit2 bit2 bit1 bit1 LSB LSB 1 2 3 4 5 6 7 8 Figure 16-6. CPHA/SS Timing MISO/MOSI Master SS Slave SS (CPHA = 0) Slave SS (CPHA = 1) Byte 1 Byte 2 Byte 3 As shown in Figure 16-4, the first SCK edge is the MSB capture strobe. Therefore, the Slave must begin driving its data before the first SCK edge, and a falling edge on the SS pin is used to start the transmission. The SS pin must be toggled high and then low between each Byte transmitted (Figure 16-6). Figure 16-5 shows an SPI transmission in which CPHA is ’1’. In this case, the Master begins driving its MOSI pin on the first SCK edge. Therefore, the Slave uses the first SCK edge as a start transmission signal. The SS pin can remain low between transmissions (Figure 16-6). This format may be preferred in systems having only one Master and only one Slave driving the MISO data line. 16.3.3 Error Conditions The following flags in the SPSTA signal SPI error conditions: 67 4235K–8051–05/08 16.3.3.1 Mode Fault (MODF) Mode Fault error in Master mode SPI indicates that the level on the Slave Select (SS) pin is inconsistent with the actual mode of the device. MODF is set to warn that there may be a multimaster conflict for system control. In this case, the SPI system is affected in the following ways: • An SPI receiver/error CPU interrupt request is generated • The SPEN bit in SPCON is cleared. This disables the SPI • The MSTR bit in SPCON is cleared When SS Disable (SSDIS) bit in the SPCON register is cleared, the MODF flag is set when the SS signal becomes ’0’. However, as stated before, for a system with one Master, if the SS pin of the Master device is pulled low, there is no way that another Master attempts to drive the network. In this case, to prevent the MODF flag from being set, software can set the SSDIS bit in the SPCON register and therefore making the SS pin as a general-purpose I/O pin. Clearing the MODF bit is accomplished by a read of SPSTA register with MODF bit set, followed by a write to the SPCON register. SPEN Control bit may be restored to its original set state after the MODF bit has been cleared. 16.3.3.2 Write Collision (WCOL) A Write Collision (WCOL) flag in the SPSTA is set when a write to the SPDAT register is done during a transmit sequence. WCOL does not cause an interruption, and the transfer continues uninterrupted. Clearing the WCOL bit is done through a software sequence of an access to SPSTA and an access to SPDAT. 16.3.3.3 Overrun Condition An overrun condition occurs when the Master device tries to send several data Bytes and the Slave devise has not cleared the SPIF bit issuing from the previous data Byte transmitted. In this case, the receiver buffer contains the Byte sent after the SPIF bit was last cleared. A read of the SPDAT returns this Byte. All others Bytes are lost. This condition is not detected by the SPI peripheral. 16.3.3.4 SS Error Flag (SSERR) A Synchronous Serial Slave Error occurs when SS goes high before the end of a received data in slave mode. SSERR does not cause in interruption, this bit is cleared by writing 0 to SPEN bit (reset of the SPI state machine). Interrupts Two SPI status flags can generate a CPU interrupt requests: Table 16-2. Flag SPIF (SP data transfer) MODF (Mode Fault) 16.3.4 SPI Interrupts Request SPI Transmitter Interrupt request SPI Receiver/Error Interrupt Request (if SSDIS = ’0’) 68 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Serial Peripheral data transfer flag, SPIF: This bit is set by hardware when a transfer has been completed. SPIF bit generates transmitter CPU interrupt requests. Mode Fault flag, MODF: This bit becomes set to indicate that the level on the SS is inconsistent with the mode of the SPI. MODF with SSDIS reset, generates receiver/error CPU interrupt requests. When SSDIS is set, no MODF interrupt request is generated. Figure 16-7 gives a logical view of the above statements. Figure 16-7. SPI Interrupt Requests Generation SPIF SPI Transmitter CPU Interrupt Request SPI Receiver/error CPU Interrupt Request SSDIS SPI CPU Interrupt Request MODF 16.3.5 Registers There are three registers in the Module that provide control, status and data storage functions. These registers are describes in the following paragraphs. 16.3.5.1 Serial Peripheral Control Register (SPCON) • The Serial Peripheral Control Register does the following: • Selects one of the Master clock rates • Configure the SPI Module as Master or Slave • Selects serial clock polarity and phase • Enables the SPI Module • Frees the SS pin for a general-purpose Table 16-3 describes this register and explains the use of each bit Table 16-3. SPCON Register SPCON - Serial Peripheral Control Register (0C3H) 7 SPR2 Bit Number 7 6 SPEN 5 SSDIS 4 MSTR Description Serial Peripheral Rate 2 Bit with SPR1 and SPR0 define the clock rate. Serial Peripheral Enable 6 SPEN Cleared to disable the SPI interface. Set to enable the SPI interface. SS Disable Cleared to enable SS in both Master and Slave modes. 5 SSDIS Set to disable SS in both Master and Slave modes. In Slave mode, this bit has no effect if CPHA =’0’. When SSDIS is set, no MODF interrupt request is generated. 3 CPOL 2 CPHA 1 SPR1 0 SPR0 Bit Mnemonic SPR2 69 4235K–8051–05/08 Bit Number Bit Mnemonic Description Serial Peripheral Master 4 MSTR Cleared to configure the SPI as a Slave. Set to configure the SPI as a Master. Clock Polarity 3 CPOL Cleared to have the SCK set to ’0’ in idle state. Set to have the SCK set to ’1’ in idle low. Clock Phase 2 CPHA Cleared to have the data sampled when the SCK leaves the idle state (see CPOL). Set to have the data sampled when the SCK returns to idle state (see CPOL). SPR2 SPR1 SPR0 Serial Peripheral Rate 1 SPR1 0 0 0 0 1 0 0 1 1 0 0 1 1 1FCLK PERIPH /2 1FCLK PERIPH /4 0 FCLK PERIPH /8 1FCLK PERIPH /16 0FCLK PERIPH /32 1FCLK PERIPH /64 0FCLK PERIPH /128 1Invalid SPR0 1 1 1 Reset Value = 0001 0100b Not bit addressable 16.3.5.2 Serial Peripheral Status Register (SPSTA) The Serial Peripheral Status Register contains flags to signal the following conditions: • Data transfer complete • Write collision • Inconsistent logic level on SS pin (mode fault error) Table 16-4 describes the SPSTA register and explains the use of every bit in the register. Table 16-4. SPSTA Register SPSTA - Serial Peripheral Status and Control register (0C4H) 7 SPIF 6 WCOL Bit Mnemonic 5 SSERR 4 MODF 3 2 1 0 - Bit Number Description Serial Peripheral Data Transfer Flag 7 SPIF Cleared by hardware to indicate data transfer is in progress or has been approved by a clearing sequence. Set by hardware to indicate that the data transfer has been completed. Write Collision Flag 6 WCOL Cleared by hardware to indicate that no collision has occurred or has been approved by a clearing sequence. Set by hardware to indicate that a collision has been detected. 70 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Bit Number Bit Mnemonic Description Synchronous Serial Slave Error Flag 5 SSERR Set by hardware when SS is de-asserted before the end of a received data. Cleared by disabling the SPI (clearing SPEN bit in SPCON). Mode Fault 4 MODF Cleared by hardware to indicate that the SS pin is at appropriate logic level, or has been approved by a clearing sequence. Set by hardware to indicate that the SS pin is at inappropriate logic level. 3 Reserved The value read from this bit is indeterminate. Do not set this bit Reserved The value read from this bit is indeterminate. Do not set this bit. Reserved The value read from this bit is indeterminate. Do not set this bit. Reserved The value read from this bit is indeterminate. Do not set this bit. 2 - 1 - 0 - Reset Value = 00X0 XXXXb Not Bit addressable 16.3.5.3 Serial Peripheral DATa Register (SPDAT) The Serial Peripheral Data Register (Table 16-5) is a read/write buffer for the receive data register. A write to SPDAT places data directly into the shift register. No transmit buffer is available in this model. A Read of the SPDAT returns the value located in the receive buffer and not the content of the shift register. Table 16-5. SPDAT Register SPDAT - Serial Peripheral Data Register (0C5H) 7 R7 6 R6 5 R5 4 R4 3 R3 2 R2 1 R1 0 R0 Reset Value = Indeterminate R7:R0: Receive data bits SPCON, SPSTA and SPDAT registers may be read and written at any time while there is no ongoing exchange. However, special care should be taken when writing to them while a transmission is on-going: • Do not change SPR2, SPR1 and SPR0 • Do not change CPHA and CPOL • Do not change MSTR • Clearing SPEN would immediately disable the peripheral • Writing to the SPDAT will cause an overflow. 71 4235K–8051–05/08 17. Interrupt System The AT89C51RD2/ED2 has a total of 9 interrupt vectors: two external interrupts (INT0 and INT1), three timer interrupts (timers 0, 1 and 2), the serial port interrupt, SPI interrupt, Keyboard interrupt and the PCA global interrupt. These interrupts are shown in Figure 17-1. Figure 17-1. Interrupt Control System IPH, IPL 3 INT0 IE0 0 3 0 3 INT1 IE1 0 TF1 3 0 3 PCA IT 0 RI TI 3 0 3 0 3 KBD IT 0 Interrupt Polling Sequence, Decreasing from High to Low Priority High Priority Interrupt TF0 TF2 EXF2 3 SPI IT 0 Low Priority Interrupt Individual Enable Global Disable Each of the interrupt sources can be individually enabled or disabled by setting or clearing a bit in the Interrupt Enable register (Table 17-4 and Table 17-6). This register also contains a global disable bit, which must be cleared to disable all interrupts at once. Each interrupt source can also be individually programmed to one out of four priority levels by setting or clearing a bit in the Interrupt Priority register (Table 17-7) and in the Interrupt Priority High register (Table 17-5 and Table 17-6) shows the bit values and priority levels associated with each combination. 72 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 17.1 Registers The PCA interrupt vector is located at address 0033H, the SPI interrupt vector is located at address 004BH and Keyboard interrupt vector is located at address 003BH. All other vectors addresses are the same as standard C52 devices. Table 17-1. Priority Level Bit Values IPH.x 0 0 1 1 IPL.x 0 1 0 1 Interrupt Level Priority 0 (Lowest) 1 2 3 (Highest) A low-priority interrupt can be interrupted by a high priority interrupt, but not by another low-priority interrupt. A high-priority interrupt can’t be interrupted by any other interrupt source. If two interrupt requests of different priority levels are received simultaneously, the request of higher priority level is serviced. If interrupt requests of the same priority level are received simultaneously, an internal polling sequence determines which request is serviced. Thus within each priority level there is a second priority structure determined by the polling sequence. 17.2 Interrupt Sources and Vector Addresses Table 17-2. Number 0 1 2 3 4 5 6 7 8 9 10 Interrupt Sources and Vector Addresses Polling Priority 0 1 2 3 4 6 7 5 8 9 10 Interrupt Source Reset INT0 Timer 0 INT1 Timer 1 UART Timer 2 PCA Keyboard SPI IE0 TF0 IE1 IF1 RI+TI TF2+EXF2 CF + CCFn (n = 0 - 4) KBDIT SPIIT Interrupt Request Vector Address 0000h 0003h 000Bh 0013h 001Bh 0023h 002Bh 0033h 003Bh 0043h 004Bh 73 4235K–8051–05/08 Table 17-3. IENO Register IEN0 - Interrupt Enable Register (A8h) 7 EA Bit Number 6 EC Bit Mnemonic Description Enable All interrupt bit Cleared to disable all interrupts. Set to enable all interrupts. PCA interrupt enable bit 6 EC Cleared to disable. Set to enable. Timer 2 overflow interrupt Enable bit Cleared to disable timer 2 overflow interrupt. Set to enable timer 2 overflow interrupt. Serial port Enable bit Cleared to disable serial port interrupt. Set to enable serial port interrupt. Timer 1 overflow interrupt Enable bit Cleared to disable timer 1 overflow interrupt. Set to enable timer 1 overflow interrupt. External interrupt 1 Enable bit Cleared to disable external interrupt 1. Set to enable external interrupt 1. Timer 0 overflow interrupt Enable bit Cleared to disable timer 0 overflow interrupt. Set to enable timer 0 overflow interrupt. External interrupt 0 Enable bit Cleared to disable external interrupt 0. Set to enable external interrupt 0. 5 ET2 4 ES 3 ET1 2 EX1 1 ET0 0 EX0 7 EA 5 ET2 4 ES 3 ET1 2 EX1 1 ET0 0 EX0 Reset Value = 0000 0000b Bit addressable 74 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 17-4. IPL0 Register IPL0 - Interrupt Priority Register (B8h) 7 Bit Number 7 6 PPCL Bit Mnemonic Description Reserved The value read from this bit is indeterminate. Do not set this bit. PCA interrupt Priority bit Refer to PPCH for priority level. Timer 2 overflow interrupt Priority bit Refer to PT2H for priority level. Serial port Priority bit Refer to PSH for priority level. Timer 1 overflow interrupt Priority bit Refer to PT1H for priority level. External interrupt 1 Priority bit Refer to PX1H for priority level. Timer 0 overflow interrupt Priority bit Refer to PT0H for priority level. External interrupt 0 Priority bit Refer to PX0H for priority level. 5 PT2L 4 PSL 3 PT1L 2 PX1L 1 PT0L 0 PX0L 6 PPCL 5 PT2L 4 PSL 3 PT1L 2 PX1L 1 PT0L 0 PX0L Reset Value = X000 0000b Bit addressable 75 4235K–8051–05/08 Table 17-5. IPH0 Register IPH0 - Interrupt Priority High Register (B7h) 7 Bit Number 7 6 PPCH Bit Mnemonic Description Reserved The value read from this bit is indeterminate. Do not set this bit. PCA interrupt Priority high bit. PPCHPPCLPriority Level 0 0Lowest 01 10 1 1Highest Timer 2 overflow interrupt Priority High bit PT2HPT2L Priority Level 0 0Lowest 0 1 1 0 1 1Highest Serial port Priority High bit PSH PSLPriority Level 0 0Lowest 0 1 1 0 1 1Highest Timer 1 overflow interrupt Priority High bit PT1HPT1L Priority Level 0 0 Lowest 0 1 1 0 1 1Highest External interrupt 1 Priority High bit PX1HPX1LPriority Level 0 0Lowest 0 1 1 0 1 1Highest Timer 0 overflow interrupt Priority High bit PT0HPT0LPriority Level 0 0Lowest 0 1 1 0 1 1Highest External interrupt 0 Priority High bit PX0H PX0LPriority Level 0 0Lowest 0 1 1 0 1 1Highest 5 PT2H 4 PSH 3 PT1H 2 PX1H 1 PT0H 0 PX0H 6 PPCH 5 PT2H 4 PSH 3 PT1H 2 PX1H 1 PT0H 0 PX0H Reset Value = X000 0000b Not bit addressable 76 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 17-6. IEN1 Register IEN1 - Interrupt Enable Register (B1h) 7 Bit Number 7 6 5 4 3 6 Bit Mnemonic Description Reserved Reserved Reserved Reserved Reserved SPI interrupt Enable bit Cleared to disable SPI interrupt. Set to enable SPI interrupt. 1 Reserved Keyboard interrupt Enable bit Cleared to disable keyboard interrupt. Set to enable keyboard interrupt. 5 4 3 2 ESPI 1 0 KBD 2 ESPI 0 KBD Reset Value = XXXX X000b Bit addressable 77 4235K–8051–05/08 Table 17-7. IPL1 Register IPL1 - Interrupt Priority Register (B2h) 7 Bit Number 7 6 Bit Mnemonic Description Reserved The value read from this bit is indeterminate. Do not set this bit. Reserved The value read from this bit is indeterminate. Do not set this bit. Reserved The value read from this bit is indeterminate. Do not set this bit. Reserved The value read from this bit is indeterminate. Do not set this bit. Reserved The value read from this bit is indeterminate. Do not set this bit. SPI interrupt Priority bit Refer to SPIH for priority level. Reserved The value read from this bit is indeterminate. Do not set this bit. Keyboard interrupt Priority bit Refer to KBDH for priority level. 5 4 3 2 SPIL 1 TWIL 0 KBDL 6 - 5 - 4 - 3 - 2 SPIL 1 - 0 KBDL Reset Value = XXXX X000b Bit addressable 78 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 17-8. IPH1 Register IPH1 - Interrupt Priority High Register (B3h) 7 Bit Number 7 6 Bit Mnemonic Description Reserved The value read from this bit is indeterminate. Do not set this bit. Reserved The value read from this bit is indeterminate. Do not set this bit. Reserved The value read from this bit is indeterminate. Do not set this bit. Reserved The value read from this bit is indeterminate. Do not set this bit. Reserved The value read from this bit is indeterminate. Do not set this bit. SPI interrupt Priority High bit SPIHSPILPriority Level 0 0Lowest 0 1 1 0 1 1Highest Reserved The value read from this bit is indeterminate. Do not set this bit. Keyboard interrupt Priority High bit KB DHKBDLPriority Level 0 0 Lowest 0 1 1 0 1 1Highest 5 4 3 2 SPIH 1 0 KBDH 6 - 5 - 4 - 3 - 2 SPIH 1 - 0 KBDH Reset Value = XXXX X000b Not bit addressable 79 4235K–8051–05/08 18. Power Management 18.1 Introduction Two power reduction modes are implemented in the AT89C51RD2/ED2. The Idle mode and the Power-Down mode. These modes are detailed in the following sections. In addition to these power reduction modes, the clocks of the core and peripherals can be dynamically divided by 2 using the X2 mode detailed in Section “Enhanced Features”, page 17. 18.2 Idle Mode Idle mode is a power reduction mode that reduces the power consumption. In this mode, program execution halts. Idle mode freezes the clock to the CPU at known states while the peripherals continue to be clocked. The CPU status before entering Idle mode is preserved, i.e., the program counter and program status word register retain their data for the duration of Idle mode. The contents of the SFRs and RAM are also retained. The status of the Port pins during Idle mode is detailed in Table 18-1. 18.2.1 Entering Idle Mode To enter Idle mode, set the IDL bit in PCON register (see Table 18-2). The AT89C51RD2/ED2 enters Idle mode upon execution of the instruction that sets IDL bit. The instruction that sets IDL bit is the last instruction executed. Note: If IDL bit and PD bit are set simultaneously, the AT89C51RD2/ED2 enters Power-Down mode. Then it does not go in Idle mode when exiting Power-Down mode. 18.2.2 Exiting Idle Mode There are two ways to exit Idle mode: 1. Generate an enabled interrupt. – Hardware clears IDL bit in PCON register which restores the clock to the CPU. Execution resumes with the interrupt service routine. Upon completion of the interrupt service routine, program execution resumes with the instruction immediately following the instruction that activated Idle mode. The general purpose flags (GF1 and GF0 in PCON register) may be used to indicate whether an interrupt occurred during normal operation or during Idle mode. When Idle mode is exited by an interrupt, the interrupt service routine may examine GF1 and GF0. 2. Generate a reset. – A logic high on the RST pin clears IDL bit in PCON register directly and asynchronously. This restores the clock to the CPU. Program execution momentarily resumes with the instruction immediately following the instruction that activated the Idle mode and may continue for a number of clock cycles before the internal reset algorithm takes control. Reset initializes the AT89C51RD2/ED2 and vectors the CPU to address C:0000h. Note: During the time that execution resumes, the internal RAM cannot be accessed; however, it is possible for the Port pins to be accessed. To avoid unexpected outputs at the Port pins, the instruction immediately following the instruction that activated Idle mode should not write to a Port pin or to the external RAM. 80 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 18.3 Power-Down Mode The Power-Down mode places the AT89C51RD2/ED2 in a very low power state. Power-Down mode stops the oscillator, freezes all clock at known states. The CPU status prior to entering Power-Down mode is preserved, i.e., the program counter, program status word register retain their data for the duration of Power-Down mode. In addition, the SFR and RAM contents are preserved. The status of the Port pins during Power-Down mode is detailed in Table 18-1. Note: VCC may be reduced to as low as VRET during Power-Down mode to further reduce power dissipation. Take care, however, that VDD is not reduced until Power-Down mode is invoked. 18.3.1 Entering Power-Down Mode To enter Power-Down mode, set PD bit in PCON register. The AT89C51RD2/ED2 enters the Power-Down mode upon execution of the instruction that sets PD bit. The instruction that sets PD bit is the last instruction executed. Exiting Power-Down Mode Note: If VCC was reduced during the Power-Down mode, do not exit Power-Down mode until VCC is restored to the normal operating level. 18.3.2 There are three ways to exit the Power-Down mode: 1. Generate an enabled external interrupt. – The AT89C51RD2/ED2 provides capability to exit from Power-Down using INT0#, INT1#. Hardware clears PD bit in PCON register which starts the oscillator and restores the clocks to the CPU and peripherals. Using INTx# input, execution resumes when the input is released (see Figure 18-1). Execution resumes with the interrupt service routine. Upon completion of the interrupt service routine, program execution resumes with the instruction immediately following the instruction that activated Power-Down mode. Note: The external interrupt used to exit Power-Down mode must be configured as level sensitive (INT0# and INT1#) and must be assigned the highest priority. In addition, the duration of the interrupt must be long enough to allow the oscillator to stabilize. The execution will only resume when the interrupt is deasserted. Exit from power-down by external interrupt does not affect the SFRs nor the internal RAM content. Note: Figure 18-1. Power-Down Exit Waveform Using INT1:0# INT1:0# OSC Active phase Power-down phase Oscillator restart phase Active phase 2. Generate a reset. – A logic high on the RST pin clears PD bit in PCON register directly and asynchronously. This starts the oscillator and restores the clock to the CPU and peripherals. Program execution momentarily resumes with the instruction immediately following the instruction that activated Power-Down mode and may 81 4235K–8051–05/08 continue for a number of clock cycles before the internal reset algorithm takes control. Reset initializes the AT89C51RD2/ED2 and vectors the CPU to address 0000h. 3. Generate an enabled external Keyboard interrupt (same behavior as external interrupt). Note: During the time that execution resumes, the internal RAM cannot be accessed; however, it is possible for the Port pins to be accessed. To avoid unexpected outputs at the Port pins, the instruction immediately following the instruction that activated the Power-Down mode should not write to a Port pin or to the external RAM. Exit from power-down by reset redefines all the SFRs, but does not affect the internal RAM content. Note: Table 18-1. Mode Reset Idle (internal code) Idle (external code) Power-Down (internal code) Power-Down (external code) Pin Conditions in Special Operating Modes Port 0 Floating Data Port 1 High Data Port 2 High Data Port 3 High Data Port 4 High Data ALE High High PSEN# High High Floating Data Data Data Data High High Data Data Data Data Data Low Low Floating Data Data Data Data Low Low 82 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 18.4 Registers Table 18-2. 7 - PCON Register PCON (S87:h) Power configuration Register 6 Bit Mnemonic 5 4 3 GF1 2 GF0 1 PD 0 IDL Bit Number 7-4 Description Reserved The value read from these bits is indeterminate. Do not set these bits. General Purpose flag 1 One use is to indicate whether an interrupt occurred during normal operation or during Idle mode. General Purpose flag 0 One use is to indicate whether an interrupt occurred during normal operation or during Idle mode. Power-Down Mode bit Cleared by hardware when an interrupt or reset occurs. Set to activate the Power-Down mode. If IDL and PD are both set, PD takes precedence. Idle Mode bit Cleared by hardware when an interrupt or reset occurs. Set to activate the Idle mode. If IDL and PD are both set, PD takes precedence. 3 GF1 2 GF0 1 PD 0 IDL Reset Value= XXXX 0000b 83 4235K–8051–05/08 19. Hardware Watchdog Timer The WDT is intended as a recovery method in situations where the CPU may be subjected to software upset. The WDT consists of a 14-bit counter and the Watchdog Timer ReSeT (WDTRST) SFR. The WDT is by default disabled from exiting reset. To enable the WDT, user must write 01EH and 0E1H in sequence to the WDTRST, SFR location 0A6H. When WDT is enabled, it will increment every machine cycle while the oscillator is running and there is no way to disable the WDT except through reset (either hardware reset or WDT overflow reset). When WDT overflows, it will drive an output RESET HIGH pulse at the RST-pin. 19.1 Using the WDT To enable the WDT, user must write 01EH and 0E1H in sequence to the WDTRST, SFR location 0A6H. When WDT is enabled, the user needs to service it by writing to 01EH and 0E1H to WDTRST to avoid WDT overflow. The 14-bit counter overflows when it reaches 16383 (3FFFH) and this will reset the device. When WDT is enabled, it will increment every machine cycle while the oscillator is running. This means the user must reset the WDT at least every 16383 machine cycle. To reset the WDT the user must write 01EH and 0E1H to WDTRST. WDTRST is a write only register. The WDT counter cannot be read or written. When WDT overflows, it will generate an output RESET pulse at the RST-pin. The RESET pulse duration is 96 x TCLK PERIPH, where TCLK PERIPH= 1/FCLK PERIPH. To make the best use of the WDT, it should be serviced in those sections of code that will periodically be executed within the time required to prevent a WDT reset. To have a more powerful WDT, a 27 counter has been added to extend the Time-out capability, ranking from 16 ms to 2s @ FOSCA = 12 MHz. To manage this feature, refer to WDTPRG register description, Table 19-1. The WDTPRG register should be configured before the WDT activation sequence, and can not be modified until next reset. Table 19-1. WDTRST Register WDTRST - Watchdog Reset Register (0A6h) 7 6 5 4 3 2 1 0 - Reset Value = XXXX XXXXb Write only, this SFR is used to reset/enable the WDT by writing 01EH then 0E1H in sequence. 84 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 19-2. WDTPRG Register WDTPRG - Watchdog Timer Out Register (0A7h) 7 Bit Number 7 6 5 4 3 2 1 0 6 Bit Mnemonic S2 S1 S0 WDT Time-out select bit 2 WDT Time-out select bit 1 WDT Time-out select bit 0 S2 0 0 0 0 1 1 1 1 S1 S0Selected Time-out 00 (214 - 1) machine cycles, 16. 3 ms @ FOSCA =12 MHz 01 (215 - 1) machine cycles, 32.7 ms @ FOSCA=12 MHz 10 (216 - 1) machine cycles, 65. 5 ms @ FOSCA=12 MHz 11 (217 - 1) machine cycles, 131 ms @ FOSCA=12 MHz 00 (218 - 1) machine cycles, 262 ms @ FOSCA=12 MHz 01 (219 - 1) machine cycles, 542 ms @ FOSCA=12 MHz 10 (220 - 1) machine cycles, 1.05 ms @ FOSCA=12 MHz 11 (221 - 1) machine cycles, 2.09 ms @ FOSCA=12 MHz Reserved The value read from this bit is undetermined. Do not try to set this bit. Description 5 4 3 2 S2 1 S1 0 S0 Reset Value = XXXX X000 19.2 WDT during Power-down and Idle In Power-down mode the oscillator stops, which means the WDT also stops. While in Powerdown mode the user does not need to service the WDT. There are 2 methods of exiting Powerdown mode: by a hardware reset or via a level activated external interrupt which is enabled prior to entering Power-down mode. When Power-down is exited with hardware reset, servicing the WDT should occur as it normally should whenever the AT89C51RD2/ED2 is reset. Exiting Power-down with an interrupt is significantly different. The interrupt is held low long enough for the oscillator to stabilize. When the interrupt is brought high, the interrupt is serviced. To prevent the WDT from resetting the device while the interrupt pin is held low, the WDT is not started until the interrupt is pulled high. It is suggested that the WDT be reset during the interrupt service routine. To ensure that the WDT does not overflow within a few states of exiting of powerdown, it is better to reset the WDT just before entering powerdown. In the Idle mode, the oscillator continues to run. To prevent the WDT from resetting the AT89C51RD2/ED2 while in Idle mode, the user should always set up a timer that will periodically exit Idle, service the WDT, and re-enter Idle mode. 85 4235K–8051–05/08 20. ONCE® Mode (ON- Chip Emulation) The ONCE mode facilitates testing and debugging of systems using AT89C51RD2/ED2 without removing the circuit from the board. The ONCE mode is invoked by driving certain pins of the AT89C51RD2/ED2; the following sequence must be exercised: • Pull ALE low while the device is in reset (RST high) and PSEN is high. • Hold ALE low as RST is deactivated. While the AT89C51RD2/ED2 is in ONCE mode, an emulator or test CPU can be used to drive the circuit. Table 20-1 shows the status of the port pins during ONCE mode. Normal operation is restored when normal reset is applied. Table 20-1. ALE Weak pullup External Pin Status During ONCE Mode PSEN Weak pullup Port 0 Float Port 1 Weak pullup Port 2 Weak pullup Port 3 Weak pullup Port I2 Float XTALA1/2 Active XTALB1/2 Active 86 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 21. Power-off Flag The power-off flag allows the user to distinguish between a “cold start” reset and a “warm start” reset. A cold start reset is the one induced by VCC switch-on. A warm start reset occurs while VCC is still applied to the device and could be generated for example by an exit from power-down. The power-off flag (POF) is located in PCON register (Table 21-1). POF is set by hardware when VCC rises from 0 to its nominal voltage. The POF can be set or cleared by software allowing the user to determine the type of reset. Table 21-1. PCON Register PCON - Power Control Register (87h) 7 SMOD1 Bit Number 7 6 SMOD0 Bit Mnemonic SMOD1 Description Serial port Mode bit 1 Set to select double baud rate in mode 1, 2 or 3. Serial port Mode bit 0 Cleared to select SM0 bit in SCON register. Set to select FE bit in SCON register. Reserved The value read from this bit is indeterminate. Do not set this bit. Power-Off Flag Cleared by software to recognize the next reset type. Set by hardware when VCC rises from 0 to its nominal voltage. Can also be set by software. General-purpose Flag Cleared by user for general-purpose usage. Set by user for general-purpose usage. General-purpose Flag Cleared by user for general-purpose usage. Set by user for general-purpose usage. Power-down mode bit Cleared by hardware when reset occurs. Set to enter power-down mode. Idle mode bit Cleared by hardware when interrupt or reset occurs. Set to enter idle mode. 5 4 POF 3 GF1 2 GF0 1 PD 0 IDL 6 SMOD0 5 - 4 POF 3 GF1 2 GF0 1 PD 0 IDL Reset Value = 00X1 0000b Not bit addressable 87 4235K–8051–05/08 22. Reduced EMI Mode The ALE signal is used to demultiplex address and data buses on port 0 when used with external program or data memory. Nevertheless, during internal code execution, ALE signal is still generated. In order to reduce EMI, ALE signal can be disabled by setting AO bit. The AO bit is located in AUXR register at bit location 0. As soon as AO is set, ALE is no longer output but remains active during MOVX and MOVC instructions and external fetches. During ALE disabling, ALE pin is weakly pulled high. Table 22-1. AUXR Register AUXR - Auxiliary Register (8Eh) 7 DPU Bit Number 6 Bit Mnemonic Description Disable Weak Pull-up 7 DPU Cleared by software to activate the permanent weak pull-up (default) Set by software to disable the weak pull-up (reduce power consumption) 6 Reserved The value read from this bit is indeterminate. Do not set this bit. Pulse length 5 M0 Cleared to stretch MOVX control: the RD and the WR pulse length is 6 clock periods (default). Set to stretch MOVX control: the RD and the WR pulse length is 30 clock periods. 4 3 XRS2 XRS1 XRAM Size XRS2 XRS1XRS0XRAM size 0 0 0256 bytes 0 2 XRS0 0 0 1 0 1 1 0 1512 bytes 0768 bytes(default) 11024 bytes 01792 bytes 5 M0 4 XRS2 3 XRS1 2 XRS0 1 EXTRAM 0 AO EXTRAM bit Cleared to access internal XRAM using MOVX @ Ri/ @ DPTR. 1 EXTRAM Set to access external memory. Programmed by hardware after Power-up regarding Hardware Security Byte (HSB), default setting, XRAM selected. ALE Output bit Cleared, ALE is emitted at a constant rate of 1/6 the oscillator frequency (or 1/3 if X2 mode is used) (default). Set, ALE is active only during a MOVX or MOVC instruction is used. 0 AO Reset Value = XX00 10’HSB. XRAM’0b Not bit addressable 88 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 23. EEPROM Data Memory This feature is available only for the AT89C51ED2 device. The 2K bytes on-chip EEPROM memory block is located at addresses 0000h to 07FFh of the XRAM/ERAM memory space and is selected by setting control bits in the EECON register. A read or write access to the EEPROM memory is done with a MOVX instruction. 23.1 Write Data Data is written by byte to the EEPROM memory block as for an external RAM memory. The following procedure is used to write to the EEPROM memory: • Check EEBUSY flag • If the user application interrupts routines use XRAM memory space: Save and disable interrupts. • Load DPTR with the address to write • Store A register with the data to be written • Set bit EEE of EECON register • Execute a MOVX @DPTR, A • Clear bit EEE of EECON register • Restore interrupts. • EEBUSY flag in EECON is then set by hardware to indicate that programming is in progress and that the EEPROM segment is not available for reading or writing. • The end of programming is indicated by a hardware clear of the EEBUSY flag. Figure 23-1 represents the optimal write sequence to the on-chip EEPROM data memory. 89 4235K–8051–05/08 Figure 23-1. Recommended EEPROM Data Write Sequence EEPROM Data Write Sequence EEBusy Cleared? Save & Disable IT EA= 0 EEPROM Data Mapping EECON = 02h (EEE=1) Data Write DPTR= Address ACC= Data Exec: MOVX @DPTR, A EEPROM Mapping EECON = 00h (EEE=0) Restore IT Last Byte to Load? 23.2 Read Data The following procedure is used to read the data stored in the EEPROM memory: • Check EEBUSY flag • If the user application interrupts routines use XRAM memory space: Save and disable interrupts. • Load DPTR with the address to read • Set bit EEE of EECON register • Execute a MOVX A, @DPTR • Clear bit EEE of EECON register • Restore interrupts. 90 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Figure 23-2. Recommended EEPROM Data Read Sequence EEPROM Data Read Sequence EEBusy Cleared? Save & Disable IT EA= 0 EEPROM Data Mapping EECON = 02h (EEE=1) Data Read DPTR= Address ACC= Data Exec: MOVX A, @DPTR Last Byte to Read? EEPROM Data Mapping EECON = 00h (EEE = 0 Restore IT 23.3 Registers Table 23-1. EECON Register EECON (0D2h) EEPROM Control Register 7 6 Bit Mnemonic 5 4 3 2 1 EEE 0 EEBUSY Bit Number 7-2 Description Reserved The value read from this bit is indeterminate. Do not set this bit. 91 4235K–8051–05/08 Bit Number Bit Mnemonic Description Enable EEPROM Space bit Set to map the EEPROM space during MOVX instructions (Write or Read to the EEPROM. Clear to map the XRAM space during MOVX. Programming Busy flag Set by hardware when programming is in progress. Cleared by hardware when programming is done. Can not be set or cleared by software. 1 EEE 0 EEBUSY Reset Value = XXXX XX00b Not bit addressable 92 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 24. Flash/EEPROM Memory The Flash memory increases EEPROM and ROM functionality with in-circuit electrical erasure and programming. It contains 64K bytes of program memory organized respectively in 512 pages of 128 bytes. This memory is both parallel and serial In-System Programmable (ISP). ISP allows devices to alter their own program memory in the actual end product under software control. A default serial loader (bootloader) program allows ISP of the Flash. The programming does not require external dedicated programming voltage. The necessary high programming voltage is generated on-chip using the standard V C C p ins of the microcontroller. 24.1 Features • Flash EEPROM Internal Program Memory • Boot vector allows user provided Flash loader code to reside anywhere in the Flash memory space. This configuration provides flexibility to the user. • Default loader in Boot ROM allows programming via the serial port without the need of a user provided loader. • Up to 64K bytes external program memory if the internal program memory is disabled (EA = 0). • Programming and erasing voltage with standard power supply • Read/Programming/Erase: – Byte-wise read without wait state – Byte or page erase and programming (10 ms) • Typical programming time (64K bytes) is 22s with on chip serial bootloader • Parallel programming with 87C51 compatible hardware interface to programmer • Programmable security for the code in the Flash • 100K write cycles • 10 years data retention 24.2 Flash Programming and Erasure The 64-K byte Flash is programmed by bytes or by pages of 128 bytes. It is not necessary to erase a byte or a page before programming. The programming of a byte or a page includes a self erase before programming. There are three methods of programming the Flash memory: 1. The on-chip ISP bootloader may be invoked which will use low level routines to program the pages. The interface used for serial downloading of Flash is the UART. 2. The Flash may be programmed or erased in the end-user application by calling lowlevel routines through a common entry point in the Boot ROM. 3. The Flash may be programmed using the parallel method by using a conventional EPROM programmer. The parallel programming method used by these devices is similar to that used by EPROM 87C51 but it is not identical and the commercially available programmers need to have support for the AT89C51RD2/ED2. The bootloader and the Application Programming Interface (API) routines are located in the BOOT ROM. 93 4235K–8051–05/08 24.3 Flash Registers and Memory Map The AT89C51RD2/ED2 Flash memory uses several registers for its management: • Hardware register can only be accessed through the parallel programming modes which are handled by the parallel programmer. • Software registers are in a special page of the Flash memory which can be accessed through the API or with the parallel programming modes. This page, called "Extra Flash Memory", is not in the internal Flash program memory addressing space. 24.3.1 Hardware Register The only hardware register of the AT89C51RD2/ED2 is called Hardware Byte or Hardware Security Byte (HSB). Table 24-1. 7 X2 Bit Number Hardware Security Byte (HSB) 6 BLJB Bit Mnemonic 5 4 3 XRAM 2 LB2 1 LB1 0 LB0 Description X2 Mode Programmed (‘0’ value) to force X2 mode (6 clocks per instruction) after reset. Unprogrammed (‘1’ Value) to force X1 mode, Standard Mode, after reset (Default). Boot Loader Jump Bit 7 X2 6 BLJB Unprogrammed (‘1’ value) to start the user’s application on next reset at address 0000h. Programmed (‘0’ value) to start the boot loader at address F800h on next reset (Default). 5 4 - Reserved Reserved XRAM config bit (only programmable by programmer tools) 3 XRAM Programmed to inhibit XRAM. Unprogrammed, this bit to valid XRAM (Default). 2-0 LB2-0 User Memory Lock Bits (only programmable by programmer tools) See Table 24-2 Boot Loader Jump Bit (BLJB) One bit of the HSB, the BLJB bit, is used to force the boot address: • When this bit is programmed (‘0’ value) the boot address is F800h. • When this bit is unprogrammed (‘1’ value) the boot address is 0000h. By default, this bit is programmed and the ISP is enabled. 24.3.2 Flash Memory Lock Bits The three lock bits provide different levels of protection for the on-chip code and data when programmed as shown in Table 24-2. 94 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 24-2. Program Lock Bits Program Lock Bits Security Level 1 LB0 U LB1 U LB2 U Protection Description No program lock features enabled. MOVC instruction executed from external program memory is disabled from fetching code bytes from internal memory, EA is sampled and latched on reset, and further parallel programming of the on chip code memory is disabled. ISP and software programming with API are still allowed. 2 P U U 3 4 X X P X U P Same as 2, also verify code memory through parallel programming interface is disabled. Same as 3, also external execution is disabled (Default). Note: U: Unprogrammed or "one" level. P: Programmed or "zero" level. X: Do not care WARNING: Security level 2 and 3 should only be programmed after Flash and code verification. These security bits protect the code access through the parallel programming interface. They are set by default to level 4. The code access through the ISP is still possible and is controlled by the "software security bits" which are stored in the extra Flash memory accessed by the ISP firmware. To load a new application with the parallel programmer, a chip erase must first be done. This will set the HSB in its inactive state and will erase the Flash memory. The part reference can always be read using Flash parallel programming modes. 24.3.3 Default Values The default value of the HSB provides parts ready to be programmed with ISP: • BLJB: Programmed force ISP operation. • X2: Unprogrammed to force X1 mode (Standard Mode). • XRAM: Unprogrammed to valid XRAM • LB2-0: Security level four to protect the code from a parallel access with maximum security. 24.3.4 Software Registers Several registers are used in factory and by parallel programmers. These values are used by Atmel ISP. These registers are in the "Extra Flash Memory" part of the Flash memory. This block is also called "XAF" or eXtra Array Flash. They are accessed in the following ways: • Commands issued by the parallel memory programmer. • Commands issued by the ISP software. • Calls of API issued by the application software. Several software registers are described in Table 24-3. Table 24-3. Mnemonic SBV Default Values Definition Software Boot Vector Default value FCh Description 95 4235K–8051–05/08 Mnemonic BSB SSB Definition Boot Status Byte Software Security Byte Copy of the Manufacturer Code Copy of the Device ID #1: Family Code Copy of the Device ID #2: Memories Size and Type Copy of the Device ID #3: Name and Revision Default value 0FFh FFh 58h D7h ECh Atmel Description C51 X2, Electrically Erasable AT89C51RD2/ED2 64KB AT89C51RD2/ED2 64KB, Revision 0 EFh After programming the part by ISP, the BSB must be cleared (00h) in order to allow the application to boot at 0000h. The content of the Software Security Byte (SSB) is described in Table 24-4 and Table 24-5. To assure code protection from a parallel access, the HSB must also be at the required level. Table 24-4. 7 Bit Number 7 Software Security Byte 6 Bit Mnemonic Description Reserved Do not clear this bit. Reserved Do not clear this bit. Reserved Do not clear this bit. Reserved Do not clear this bit. Reserved Do not clear this bit. Reserved Do not clear this bit. User Memory Lock Bits See Table 24-5 5 4 3 2 1 LB1 0 LB0 6 - 5 - 4 - 3 - 2 - 1-0 LB1-0 The two lock bits provide different levels of protection for the on-chip code and data, when programmed as shown in Table 24-5. 96 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 24-5. User Memory Lock Bits of the SSB Program Lock Bits Security Level 1 2 3 LB0 1 0 X LB1 1 1 0 Protection Description No program lock features enabled. ISP programming of the Flash is disabled. Same as 2, also verify through ISP programming interface is disabled. Note: X: Do not care WARNING: Security level 2 and 3 should only be programmed after Flash verification. 24.4 Flash Memory Status AT89C51RD2/ED2 parts are delivered in standard with the ISP ROM bootloader. After ISP or parallel programming, the possible contents of the Flash memory are summarized in Figure 24-1: Figure 24-1. Flash Memory Possible Contents FFFFh Virgin Application Virgin or Application Dedicated ISP Application Virgin or Application Virgin or Application Dedicated ISP After Parallel Programming After Parallel Programming After Parallel Programming 0000h Default After ISP After ISP 24.5 Memory Organization When the EA pin is high, the processor fetches instructions from internal program Flash. If the EA pin is tied low, all program memory fetches are from external memory. 24.6 24.6.1 Bootloader Architecture Introduction The bootloader manages communication according to a specifically defined protocol to provide the whole access and service on Flash memory. Furthermore, all accesses and routines can be called from the user application. 97 4235K–8051–05/08 Figure 24-2. Diagram Context Description Access Via Specific Protocol Bootloader Flash Memory Access From User Application 24.6.2 Acronyms ISP: In-System Programming SBV: Software Boot Vector BSB: Boot Status Byte SSB: Software Security Byte HW: Hardware Byte 98 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 24.6.3 Functional Description Figure 24-3. Bootloader Functional Description External Host with Specific Protocol Communication User Application ISP Communication Management User Call Management (API) Flash Memory Management Flash Memory On the above diagram, the on-chip bootloader processes are: • ISP Communication Management The purpose of this process is to manage the communication and its protocol between the onchip bootloader and a external device. The on-chip ROM implements a serial protocol (see section “Bootloader Protocol”). This process translate serial communication frame (UART) into Flash memory access (read, write, erase, etc.). • User Call Management Several Application Program Interface (API) calls are available for use by an application program to permit selective erasing and programming of Flash pages. All calls are made through a common interface (API calls), included in the ROM bootloader. The programming functions are selected by setting up the microcontroller’s registers before making a call to a common entry point (0xFFF0). Results are returned in the registers. The purpose on this process is to translate the registers values into internal Flash Memory Management. • Flash Memory Management This process manages low level access to Flash memory (performs read and write access). 99 4235K–8051–05/08 24.6.4 Bootloader Functionality The bootloader can be activated by two means: Hardware conditions or regular boot process. The Hardware conditions (EA = 1, PSEN = 0) during the Reset# falling edge force the on-chip bootloader execution. This allows an application to be built that will normally execute the end user’s code but can be manually forced into default ISP operation. As PSEN is a an output port in normal operating mode after reset, user application should take care to release PSEN after falling edge of reset signal. The hardware conditions are sampled at reset signal falling edge, thus they can be released at any time when reset input is low. To ensure correct microcontroller startup, the PSEN pin should not be tied to ground during power-on (See Figure 24-4). Figure 24-4. Hardware conditions typical sequence during power-on. VCC PSEN RST The on-chip bootloader boot process is shown Figure 24-5. Table 24-6. Bootloader Process Description Purpose Hardware Conditions The Hardware Conditions force the bootloader execution whatever BLJB, BSB and SBV values. The Boot Loader Jump Bit forces the application execution. BLJB = 0 => Bootloader execution BLJB = 1 => Application execution BLJB The BLJB is a fuse bit in the Hardware Byte. It can be modified by hardware (programmer) or by software (API). Note: The BLJB test is performed by hardware to prevent any program execution. The Software Boot Vector contains the high address of customer bootloader stored in the application. SBV = FCh (default value) if no customer bootloader in user Flash. Note: The customer bootloader is called by JMP [SBV]00h instruction. SBV 100 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 24.6.5 Boot Process Figure 24-5. Bootloader Process RESET If BLJB = 0 then ENBOOT Bit (AUXR1) is Set else ENBOOT Bit (AUXR1) is Cleared Yes (PSEN = 0, EA = 1, and ALE =1 or Not Connected) Hardware Hardware Condition? BLJB = 1 ENBOOT = 0 BLJB!= 0 ? BLJB = 0 ENBOOT = 1 Software BSB = 00h ? PC = 0000h User Application SBV = FCh ? USER BOOT LOADER Atmel BOOT LOADER PC= [SBV]00h 101 4235K–8051–05/08 24.7 24.7.1 ISP Protocol Description Physical Layer The UART used to transmit information has the following configuration: • Character: 8-bit data • Parity: none • Stop: 2 bits • Flow control: none • Baudrate: autobaud is performed by the bootloader to compute the baudrate chosen by the host. 24.7.2 Frame Description The Serial Protocol is based on the Intel Hex-type records. Intel Hex records consist of ASCII characters used to represent hexadecimal values and are summarized below. Figure 24-6. Intel Hex Type Frame Record Mark ’:’ 1-byte Reclen 1-byte Load Offset 2-bytes Record Type 1-byte Data or Info n-bytes Checksum 1-byte • Record Mark: Record Mark is the start of frame. This field must contain ’:’. • Reclen: Reclen specifies the number of bytes of information or data which follows the Record Type field of the record. • Load Offset: Load Offset specifies the 16-bit starting load offset of the data bytes, therefore this field is used only for Data Program Record (see Section “ISP Commands Summary”). • Record Type: Record Type specifies the command type. This field is used to interpret the remaining information within the frame. The encoding for all the current record types is described in Section “ISP Commands Summary”. • Data/Info: Data/Info is a variable length field. It consists of zero or more bytes encoded as pairs of hexadecimal digits. The meaning of data depends on the Record Type. • Checksum: The two’s complement of the 8-bit bytes that result from converting each pair of ASCII hexadecimal digits to one byte of binary, and including the Reclen field to and including the last byte of the Data/Info field. Therefore, the sum of all the ASCII pairs in a record after converting to binary, from the Reclen field to and including the Checksum field, is zero. 102 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 24.8 24.8.1 Functional Description Software Security Bits (SSB) The SSB protects any Flash access from ISP command. The command "Program Software Security Bit" can only write a higher priority level. There are three levels of security: • level 0: NO_SECURITY (FFh) This is the default level. From level 0, one can write level 1 or level 2. • level 1: WRITE_SECURITY (FEh) For this level it is impossible to write in the Flash memory, BSB and SBV. The Bootloader returns ’P’ on write access. From level 1, one can write only level 2. • level 2: RD_WR_SECURITY (FCh The level 2 forbids all read and write accesses to/from the Flash/EEPROM memory. The Bootloader returns ’L’ on read or write access. Only a full chip erase in parallel mode (using a programmer) or ISP command can reset the software security bits. From level 2, one cannot read and write anything. Table 24-7. Software Security Byte Behavior Level 0 Level 1 Read-only access allowed Read-only access allowed Read-only access allowed Write level 2 allowed Read-only access allowed Read-only access allowed Not allowed Allowed Allowed Level 2 Any access not allowed Any access not allowed Any access not allowed Read-only access allowed Read-only access allowed Read-only access allowed Not allowed Allowed Allowed Flash/EEPROM Fuse Bit BSB & SBV SSB Manufacturer Info Bootloader Info Erase Block Full Chip Erase Blank Check Any access allowed Any access allowed Any access allowed Any access allowed Read-only access allowed Read-only access allowed Allowed Allowed Allowed 24.8.2 Full Chip Erase The ISP command "Full Chip Erase" erases all user Flash memory (fills with FFh) and sets some bytes used by the bootloader at their default values: • BSB = FFh 103 4235K–8051–05/08 • SBV = FCh • SSB = FFh The Full Chip Erase does not affect the bootloader. 24.8.3 Checksum Error When a checksum error is detected, send ‘X’ followed with CR&LF. 24.9 24.9.1 Flow Description Overview An initialization step must be performed after each Reset. After microcontroller reset, the bootloader waits for an autobaud sequence (see section ‘Autobaud Performances’). When the communication is initialized, the protocol depends on the record type requested by the host. FLIP, a software utility to implement ISP programming with a PC, is available from the Atmel web site. 24.9.2 Communication Initialization The host initializes the communication by sending a ’U’ character to help the bootloader to compute the baudrate (autobaud). Figure 24-7. Initialization Host Init Communication "U" Bootloader Performs Autobaud Sends Back “U” Character If (Not Received "U") Else Communication Opened "U" 24.9.3 Autobaud Performances The ISP feature allows a wide range of baud rates in the user application. It is also adaptable to a wide range of oscillator frequencies. This is accomplished by measuring the bit-time of a single bit in a received character. This information is then used to program the baud rate in terms of timer counts based on the oscillator frequency. The ISP feature requires that an initial character (an uppercase U) be sent to the AT89C51RD2/ED2 to establish the baud rate. Table show the autobaud capability. Table 24-8. Autobaud Performances Frequency (MHz) Baudrate (kHz) 2400 1.8432 OK 2 OK 2.4576 OK 3 OK 3.6864 OK 4 OK 5 OK 6 OK 7.3728 OK 104 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 24-8. Autobaud Performances (Continued) Frequency (MHz) Baudrate (kHz) 4800 9600 19200 38400 57600 115200 1.8432 OK OK OK - 2 - 2.4576 OK OK OK OK - 3 OK OK OK 3.6864 OK OK OK OK 4 OK OK - 5 OK OK OK - 6 OK OK OK OK - 7.3728 OK OK OK OK OK OK - OK - Frequency (MHz) Baudrate (kHz) 2400 4800 9600 19200 38400 57600 115200 8 OK OK OK OK - 10 OK OK OK OK - 11.0592 OK OK OK OK OK OK OK 12 OK OK OK OK OK - 14.746 OK OK OK OK OK OK OK 16 OK OK OK OK OK OK - 20 OK OK OK OK OK OK - 24 OK OK OK OK OK OK - 26.6 OK OK OK OK OK OK - 24.9.4 Command Data Stream Protocol All commands are sent using the same flow. Each frame sent by the host is echoed by the bootloader. Figure 24-8. Command Flow Host Sends First Character of the Frame Bootloader ":" ":" If (not received ":") Else Sends Echo and Start Reception Sends Frame (made of 2 ASCII Characters Per Byte) Echo Analysis Gets Frame, and Sends Back Echo for Each Received Byte 105 4235K–8051–05/08 24.9.5 Write/Program Commands Description This flow is common to the following frames: • Flash/EEPROM Programming Data Frame • EOF or Atmel Frame (only Programming Atmel Frame) • Config Byte Programming Data Frame • Baud Rate Frame Figure 24-9. Write/Program Flow Host Send Write Command Bootloader Write Command Wait Write Command OR Wait Checksum Error COMMAND ABORTED Checksum Error ’X’ & CR & LF Send Checksum Error NO_SECURITY OR Wait Security Error COMMAND ABORTED ’P’ & CR & LF Send Security Error Wait Programming Wait COMMAND_OK COMMAND FINISHED ’.’ & CR & LF Send COMMAND_OK 106 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 24.9.5.1 Example Programming Data (write 55h at address 0010h in the Flash) HOST BOOTLOADER : 01 0010 00 55 9A : 01 0010 00 55 9A . CR LF Programming Atmel function (write SSB to level 2) HOST BOOTLOADER : 02 0000 03 05 01 F5 : 02 0000 03 05 01 F5. CR LF Writing Frame (write BSB to 55h) HOST BOOTLOADER : 03 0000 03 06 00 55 9F : 03 0000 03 06 00 55 9F . CR LF 24.9.6 Blank Check Command Description Figure 24-10. Blank Check Flow Host Send Blank Check Command Bootloader Blank Check Command Wait Blank Check Command OR Wait Checksum Error COMMAND ABORTED Checksum Error ’X’ & CR & LF Send Checksum Error Flash Blank OR Wait COMMAND_OK COMMAND FINISHED ’.’ & CR & LF Send COMMAND_OK Wait Address not Erased COMMAND FINISHED address & CR & LF Send First Address not Erased 107 4235K–8051–05/08 24.9.6.1 Example Blank Check ok HOST BOOTLOADER : 05 0000 04 0000 7FFF 01 78 : 05 0000 04 0000 7FFF 01 78 . CR LF Blank Check ok at address xxxx HOST BOOTLOADER : 05 0000 04 0000 7FFF 01 78 : 05 0000 04 0000 7FFF 01 78 xxxx CR LF Blank Check with checksum error HOST BOOTLOADER : 05 0000 04 0000 7FFF 01 70 : 05 0000 04 0000 7FFF 01 70 X CR LF CR LF 108 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 24.9.7 Display Data Description Figure 24-11. Display Flow Host Send Display Command Bootloader Display Command Wait Display Command OR Wait Checksum Error COMMAND ABORTED Checksum error ’X’ & CR & LF Send Checksum Error RD_WR_SECURITY OR Wait Security Error COMMAND ABORTED ’L’ & CR & LF Send Security Error Read Data All Data Read Complet Frame Wait Display Data "Address = " "Reading Value" CR & LF Send Display Data All Data Read All Data Read COMMAND FINISHED COMMAND FINISHED 24.9.7.1 Example Display data from address 0000h to 0020h HOST BOOTLOADER BOOTLOADER BOOTLOADER BOOTLOADER : 05 0000 04 0000 0020 00 D7 : 05 0000 04 0000 0020 00 D7 0000=-----data------ CR LF (16 data) 0010=-----data------ CR LF (16 data) 0020=data CR LF ( 1 data) 24.9.8 Read Function Description This flow is similar for the following frames: 109 4235K–8051–05/08 • Reading Frame • EOF Frame/ Atmel Frame (only reading Atmel Frame) Figure 24-12. Read Flow Host Send Read Command Bootloader Read Command Wait Read Command OR Wait Checksum Error COMMAND ABORTED Checksum error ’X’ & CR & LF Send Checksum error RD_WR_SECURITY OR Wait Security Error COMMAND ABORTED ’L’ & CR & LF Send Security error Read Value Wait Value of Data COMMAND FINISHED ’value’ & ’.’ & CR & LF Send Data Read 24.9.8.1 Example Read function (read SBV) HOST BOOTLOADER HOST BOOTLOADER : 02 0000 05 07 02 F0 : 02 0000 05 07 02 F0 Value . CR LF : 02 0000 01 02 00 FB : 02 0000 01 02 00 FB Value . CR LF Atmel Read function (read Bootloader version) 24.9.9 ISP Commands Summary ISP Commands Summary Command Name Program Code Data[0] Data[1] Command Effect Program Nb Code Byte. Table 24-9. Command 00h Bootloader will accept up to 128 (80h) data bytes. The data bytes should be 128 byte page flash boundary. 110 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 24-9. Command ISP Commands Summary (Continued) Command Name Data[0] Data[1] 00h 20h 01h 40h 80h C0h 03h 04h 00h 00h 00h 05h 01h 00h 06h 01h 07h Program SBV (value to write in data[2]) Full Chip Erase (This command needs about 6 sec to be executed) Program SSB level 2 Program BSB (value to write in data[2]) Command Effect Erase block0 (0000h-1FFFh) Erase block1 (2000h-3FFFh) Erase block2 (4000h-7FFFh) Erase block3 (8000h- BFFFh) Erase block4 (C000h- FFFFh) Hardware Reset Erase SBV & BSB Program SSB level 1 03h Write Function 0Ah 04h 08h Program BLJB fuse (value to write in data[2]) Program X2 fuse (value to write in data[2]) Display Code Blank Check Display EEPROM data Manufacturer Id Device Id #1 Device Id #2 Device Id #3 Read SSB Read BSB Read SBV Read Extra Byte Read Hardware Byte Read Device Boot ID1 Read Device Boot ID2 Read Bootloader Version Program Nn EEprom Data Byte. Bootloader will accept up to 128 (80h) data bytes. Data[0:1] = start address Data [2:3] = end address 04h Display Function Data[4] = 00h:Display Code Data[4] = 01h: Blank check Data[4] = 02h: Display EEPROM 00h 01h 00h 02h 03h 00h 01h 05h Read Function 07h 02h 06h 0Bh 0Eh 01h 0Fh 07h Program EEPROM data 00h 00h 00h 111 4235K–8051–05/08 24.10 API Call Description The IAP allows to reprogram a microcontroller on-chip Flash memory without removing it from the system and while the embedded application is running. The user application can call some Application Programming Interface (API) routines allowing IAP. These API are executed by the bootloader. To call the corresponding API, the user must use a set of Flash_api routines which can be linked with the application. Example of Flash_api routines are available on the Atmel web site on the software application note: C Flash Drivers for the AT89C51RD2/ED2 The API calls description and arguments are shown in Table 24-10. 24.10.1 Process The application selects an API by setting R1, ACC, DPTR0 and DPTR1 registers. All calls are made through a common interface “USER_CALL” at the address FFF0h. The jump at the USER_CALL must be done by LCALL instruction to be able to comeback in the application. Before jump at the USER_CALL, the bit ENBOOT in AUXR1 register must be set. 24.10.2 Constraints The interrupts are not disabled by the bootloader. Interrupts must be disabled by user prior to jump to the USER_CALL, then re-enabled when returning. Interrupts must also be disabled before accessing EEPROM Data then re-enabled after. The user must take care of hardware watchdog before launching a Flash operation. Table 24-10. API Call Summary Command READ MANUF ID READ DEVICE ID1 READ DEVICE ID2 READ DEVICE ID3 R1 00h 00h 00h 00h A XXh XXh XXh XXh DPTR0 0000h 0001h 0002h 0003h DPH = 00h DPH = 20h ERASE BLOCK 01h XXh DPH = 40h DPH = 80h DPH = C0h PROGRAM DATA BYTE 02h Vaue to write Address of byte to program XXh ACC = 0: DONE 00h ACC = DPH DPTR1 XXh XXh XXh XXh Returned Value ACC = Manufacturer Id ACC = Device Id 1 ACC = Device Id 2 ACC = Device Id 3 Command Effect Read Manufacturer identifier Read Device identifier 1 Read Device identifier 2 Read Device identifier 3 Erase block 0 Erase block 1 Erase block 2 Erase block 3 Erase block 4 Program up one data byte in the on-chip flash memory. 112 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 24-10. API Call Summary (Continued) Command R1 A DPTR0 DPH = 00h DPL = 00h DPH = 00h DPL = 01h PROGRAM SSB 05h XXh DPH = 00h DPL = 10h DPH = 00h DPL = 11h PROGRAM BSB PROGRAM SBV READ SSB READ BSB READ SBV 06h 06h 07h 07h 07h New BSB value New SBV value XXh XXh XXh Number of byte to program Fuse value 00h or 01h Fuse value 00h or 01h XXh XXh XXh XXh 0000h 0001h 0000h 0001h 0002h Address of the first byte to program in the Flash memory 0008h XXh XXh XXh XXh XXh Address in XRAM of the first data to program none none ACC = SSB ACC = BSB ACC = SBV 00h ACC = SSB value Set SSB level 0 DPTR1 Returned Value Command Effect Set SSB level 1 Set SSB level 2 Set SSB level 1 Program boot status byte Program software boot vector Read Software Security Byte Read Boot Status Byte Read Software Boot Vector Program up to 128 bytes in user Flash. ACC = 0: DONE Remark: number of bytes to program is limited such as the Flash write remains in a single 128 bytes page. Hence, when ACC is 128, valid values of DPL are 00h, or, 80h. Program X2 fuse bit with ACC PROGRAM DATA PAGE 09h PROGRAM X2 FUSE 0Ah XXh none PROGRAM BLJB FUSE READ HSB READ BOOT ID1 READ BOOT ID2 READ BOOT VERSION 0Ah 0Bh 0Eh 0Eh 0Fh 0004h XXXXh DPL = 00h DPL = 01h XXXXh XXh XXh XXh XXh XXh none ACC = HSB ACC = ID1 ACC = ID2 ACC = Boot_Version Program BLJB fuse bit with ACC Read Hardware Byte Read boot ID1 Read boot ID2 Read bootloader version 113 4235K–8051–05/08 25. Electrical Characteristics 25.1 Absolute Maximum Ratings Note: Stresses at or above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions may affect device reliability. Power dissipation is based on the maximum allowable die temperature and the thermal resistance of the package. I = industrial ........................................................-40°C to 85°C Storage Temperature .................................... -65°C to + 150°C Voltage on VCC to VSS ......................................-0.5V to + 6.5V VVoltage on Any Pin to VSS .......................-0.5V to VCC + 0.5V Power Dissipation ........................................................... 1 W(2) 25.2 DC Parameters for Standard Voltage TA = -40°C to +85°C; VSS = 0V; VCC =2.7V to 5.5V and F = 0 to 40 MHz (both internal and external code execution) VCC =4.5V to 5.5V and F = 0 to 60 MHz (internal code execution only) Symbol VIL VIH VIH1 Parameter Input Low Voltage Input High Voltage except RST, XTAL1 Input High Voltage RST, XTAL1 Min -0.5 0.2 VCC + 0.9 0.7 VCC Typ Max 0.2 VCC - 0.1 VCC + 0.5 VCC + 0.5 Unit V V V VCC = 4.5V to 5.5V 0.3 0.45 VOL Output Low Voltage, ports 1, 2, 3, 4 (6) 1.0 V V V IOL = 100 µA(4) IOL = 1.6 mA(4) IOL = 3.5 mA(4) VCC = 2.7V to 5.5V 0.45 V IOL = 0.8 mA(4) VCC = 4.5V to 5.5V 0.3 0.45 VOL1 Output Low Voltage, port 0, ALE, PSEN (6) 1.0 V V V IOL = 200 µA(4) IOL = 3.2 mA(4) IOL = 7.0 mA(4) VCC = 2.7V to 5.5V 0.45 V IOL = 1.6 mA(4) VCC = 5V ± 10% VCC - 0.3 VCC - 0.7 VOH Output High Voltage, ports 1, 2, 3, 4 VCC - 1.5 V V V IOH = -10 µA IOH = -30 µA IOH = -60 µA Test Conditions VCC = 2.7V to 5.5V 0.9 VCC V IOH = -10 µA 114 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 TA = -40°C to +85°C; VSS = 0V; VCC =2.7V to 5.5V and F = 0 to 40 MHz (both internal and external code execution) VCC =4.5V to 5.5V and F = 0 to 60 MHz (internal code execution only) (Continued) Symbol Parameter Min Typ Max Unit Test Conditions VCC = 5V ± 10% VCC - 0.3 VCC - 0.7 VOH1 Output High Voltage, port 0, ALE, PSEN VCC - 1.5 V V V IOH = -200 µA IOH = -3.2 mA IOH = -7.0 mA VCC = 2.7V to 5.5V 0.9 VCC RRST IIL ILI ITL CIO IPD ICCOP ICCIDLE ICCWRITE tWRITE VPFDP VPFDM Vhyst Vcc dV/dt RST Pull-down Resistor Logical 0 Input Current ports 1, 2, 3, 4 and 5 Input Leakage Current Logical 1 to 0 Transition Current, ports 1, 2, 3, 4 Capacitance of I/O Buffer Power-down Current Power Supply Current on normal mode Power Supply Current on idle mode Power Supply Current on flash or EEdata write Flash or EEdata programming time Internal POR/PFD VPFDP threshold Internal POR/PFD VPFDM threshold Internal POR/PFD Hysteresys Maximum Vcc Power supply slew rate(7) 7 2.25 2.15 70 2.5 2.35 140 75 50 200(5) 250 -50 ±10 -650 10 150 0.4 x Frequency (MHz) + 5 0.3 x Frequency (MHz) + 5 0.8 x Frequency (MHz) + 15 17 2.69 2.62 250 0.1 V kΩ µA µA µA pF µA mA mA mA ms V V mV V/µs VIN = 0.45V 0.45V < VIN < VCC VIN = 2.0V FC = 3 MHz TA = 25°C 2.7 < VCC < 5.5V(3) VCC = 5.5V(1) VCC = 5.5V(2) VCC = 5.5V 2.7 < VCC < 5.5V IOH = -10 µA Notes: 1. Operating ICC is measured with all output pins disconnected; XTAL1 driven with TCLCH, TCHCL = 5 ns (see Figure 25-4), VIL = VSS + 0.5V, VIH = VCC - 0.5V; XTAL2 N.C.; EA = RST = Port 0 = VCC. ICC would be slightly higher if a crystal oscillator used (see Figure 25-1). 2. Idle ICC is measured with all output pins disconnected; XTAL1 driven with TCLCH, TCHCL = 5 ns, VIL = VSS + 0.5V, VIH = VCC 0.5V; XTAL2 N.C; Port 0 = VCC; EA = RST = VSS (see Figure 25-2). 3. Power-down ICC is measured with all output pins disconnected; EA = VSS, PORT 0 = VCC; XTAL2 NC.; RST = VSS (see Figure 25-3). 4. Capacitance loading on Ports 0 and 2 may cause spurious noise pulses to be superimposed on the VOLS of ALE and Ports 1 and 3. The noise is due to external bus capacitance discharging into the Port 0 and Port 2 pins when these pins make 1 to 0 transitions during bus operation. In the worst cases (capacitive loading 100 pF), the noise pulse on the ALE line may exceed 0.45V with maxi VOL peak 0.6V. A Schmitt Trigger use is not necessary. 5. Typical values are based on a limited number of samples and are not guaranteed. The values listed are at room temperature and 5V. 6. Under steady state (non-transient) conditions, IOL must be externally limited as follows: Maximum IOL per port pin: 10 mA Maximum IOL per 8-bit port: 115 4235K–8051–05/08 Port 0: 26 mA Ports 1, 2 and 3: 15 mA Maximum total IOL for all output pins: 71 mA If IOL exceeds the test condition, VOL may exceed the related specification. Pins are not guaranteed to sink current greater than the listed test conditions. 7. The maximum dV/dt value specifies the maximum Vcc drop to issure no internal POR/PFD reset. Figure 25-1. ICC Test Condition, Active Mode VCC ICC VCC VCC RST (NC) CLOCK SIGNAL XTAL2 XTAL1 VSS All other pins are disconnected. P0 EA VCC Figure 25-2. ICC Test Condition, Idle Mode VCC ICC VCC P0 RST (NC) CLOCK SIGNAL XTAL2 XTAL1 VSS All other pins are disconnected. EA VCC Figure 25-3. ICC Test Condition, Power-down Mode VCC ICC VCC P0 RST (NC) XTAL2 XTAL1 VSS All other pins are disconnected. EA VCC 116 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Figure 25-4. Clock Signal Waveform for ICC Tests in Active and Idle Modes VCC-0.5V 0.45V TCLCH TCHCL TCLCH = TCHCL = 5ns. 0.7VCC 0.2VCC-0.1 25.3 25.3.1 AC Parameters Explanation of the AC Symbols Each timing symbol has 5 characters. The first character is always a “T” (stands for time). The other characters, depending on their positions, stand for the name of a signal or the logical status of that signal. The following is a list of all the characters and what they stand for. Example:TAVLL = Time for Address Valid to ALE Low. TLLPL = Time for ALE Low to PSEN Low. (Load Capacitance for port 0, ALE and PSEN = 100 pF; Load Capacitance for all other outputs = 80 pF.) Table 25-1 Table 25-4, and Table 25-7 give the description of each AC symbols. Table 25-2, Table 25-3, Table 25-5 and Table 25-8 gives the range for each AC parameter. Table 25-2, Table 25-3 and Table 25-9 give the frequency derating formula of the AC parameter for each speed range description. To calculate each AC symbols. take the x value in the correponding column (-M) and use this value in the formula. Example: TLLIU for -M and 20 MHz, Standard clock. x = 35 ns T 50 ns TCCIV = 4T - x = 165 ns 117 4235K–8051–05/08 25.3.2 External Program Memory Characteristics Table 25-1. Symbol Description Symbol T TLHLL TAVLL TLLAX TLLIV TLLPL TPLPH TPLIV TPXIX TPXIZ TAVIV TPLAZ Parameter Oscillator clock period ALE pulse width Address Valid to ALE Address Hold After ALE ALE to Valid Instruction In ALE to PSEN PSEN Pulse Width PSEN to Valid Instruction In Input Instruction Hold After PSEN Input Instruction Float After PSEN Address to Valid Instruction In PSEN Low to Address Float Table 25-2. AC Parameters for a Fix Clock Symbol Min T TLHLL TAVLL TLLAX TLLIV TLLPL TPLPH TPLIV TPXIX TPXIZ TAVIV TPLAZ 0 10 80 10 5 50 30 25 35 5 5 n 65 -M Max ns ns ns ns ns ns ns ns ns ns ns ns Units 118 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 25-3. AC Parameters for a Variable Clock Symbol TLHLL TAVLL TLLAX TLLIV TLLPL TPLPH TPLIV TPXIX TPXIZ TAVIV TPLAZ Type Min Min Min Max Min Min Max Min Max Max Max Standard Clock 2T-x T-x T-x 4T-x T-x 3T-x 3T-x x T-x 5T-x x X2 Clock T-x 0.5 T - x 0.5 T - x 2T-x 0.5 T - x 1.5 T - x 1.5 T - x x 0.5 T - x 2.5 T - x x X parameter for -M range 15 20 20 35 15 25 45 0 15 45 10 Units ns ns ns ns ns ns ns ns ns ns ns 25.3.3 External Program Memory Read Cycle 12 TCLCL TLHLL ALE TLLIV TLLPL TPLPH PSEN TLLAX TAVLL INSTR IN A0-A7 TAVIV PORT 2 ADDRESS OR SFR-P2 ADDRESS A8-A15 ADDRESS A8-A15 TPLIV TPLAZ TPXAV TPXIZ A0-A7 INSTR IN TPXIX INSTR IN PORT 0 25.3.4 External Data Memory Characteristics 119 4235K–8051–05/08 Table 25-4. Symbol Description Symbol TRLRH TWLWH TRLDV TRHDX TRHDZ TLLDV TAVDV TLLWL TAVWL TQVWX TQVWH TWHQX TRLAZ TWHLH Parameter RD Pulse Width WR Pulse Width RD to Valid Data In Data Hold After RD Data Float After RD ALE to Valid Data In Address to Valid Data In ALE to WR or RD Address to WR or RD Data Valid to WR Transition Data Set-up to WR High Data Hold After WR RD Low to Address Float RD or WR High to ALE high Table 25-5. AC Parameters for a Fix Clock -M Symbol TRLRH TWLWH TRLDV TRHDX TRHDZ TLLDV TAVDV TLLWL TAVWL TQVWX TQVWH TWHQX TRLAZ TWHLH 45 70 5 155 10 0 5 45 0 25 155 160 105 Min 125 125 95 Max Units ns ns ns ns ns ns ns ns ns ns ns ns ns ns 120 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 25-6. AC Parameters for a Variable Clock Type Min Min Max Min Max Max Max Min Max Min Min Min Min Max Min Max Standard Clock 6T-x 6T-x 5T-x x 2T-x 8T-x 9T-x 3T-x 3T+x 4T-x T-x 7T-x T-x x T-x T+x X2 Clock 3T-x 3T-x 2.5 T - x x T-x 4T -x 4.5 T - x 1.5 T - x 1.5 T + x 2T-x 0.5 T - x 3.5 T - x 0.5 T - x x 0.5 T - x 0.5 T + x X parameter for -M range 25 25 30 0 25 45 65 30 30 30 20 20 15 0 20 20 Units ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns Symbol TRLRH TWLWH TRLDV TRHDX TRHDZ TLLDV TAVDV TLLWL TLLWL TAVWL TQVWX TQVWH TWHQX TRLAZ TWHLH TWHLH 25.3.5 External Data Memory Write Cycle ALE TWHLH PSEN TLLWL TWLWH WR TLLAX PORT 0 A0-A7 TAVWL PORT 2 ADDRESS OR SFR-P2 ADDRESS A8-A15 OR SFR P2 TQVWX TQVWH DATA OUT TWHQX 121 4235K–8051–05/08 25.3.6 External Data Memory Read Cycle ALE TLLDV TWHLH PSEN TLLWL TRLRH TRHDZ TRHDX DATA IN TRLAZ ADDRESS A8-A15 OR SFR P2 RD TAVDV TLLAX PORT 0 A0-A7 TAVWL PORT 2 ADDRESS OR SFR-P2 25.3.7 Serial Port Timing - Shift Register Mode Table 25-7. Symbol Description Symbol TXLXL TQVHX TXHQX TXHDX TXHDV Parameter Serial port clock cycle time Output data set-up to clock rising edge Output data hold after clock rising edge Input data hold after clock rising edge Clock rising edge to input data valid Table 25-8. AC Parameters for a Fix Clock -M Symbol TXLXL TQVHX TXHQX TXHDX TXHDV Min 300 200 30 0 117 Max Units ns ns ns ns ns 122 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Table 25-9. AC Parameters for a Variable Clock Type Min Min Min Min Max Standard Clock 12 T 10 T - x 2T-x x 10 T - x X2 Clock 6T 5T-x T-x x 5 T- x 50 20 0 133 X Parameter For -M Range Units ns ns ns ns ns Symbol TXLXL TQVHX TXHQX TXHDX TXHDV 25.3.8 Shift Register Timing Waveforms INSTRUCTION ALE 0 1 2 3 4 5 6 7 8 TXLXL CLOCK TQVXH OUTPUT DATA WRITE to SBUF INPUT DATA CLEAR RI 0 TXHDV VALID VALID TXHQX 1 2 TXHDX VALID VALID VALID VALID VALID 3 4 5 6 7 SET TI VALID SET RI 25.3.9 External Clock Drive Waveforms VCC-0.5V 0.45V 0.7VCC 0.2VCC-0.1 TCHCL TCLCX TCLCL TCHCX TCLCH 25.3.10 AC Testing Input/Output Waveforms VCC -0.5V INPUT/OUTPUT 0.45V 0.2 VCC + 0.9 0.2 VCC - 0.1 AC inputs during testing are driven at VCC - 0.5 for a logic “1” and 0.45V for a logic “0”. Timing measurement are made at VIH min for a logic “1” and VIL max for a logic “0”. 123 4235K–8051–05/08 25.3.11 Float Waveforms FLOAT VOH - 0.1V VOL + 0.1V VLOAD VLOAD + 0.1V VLOAD - 0.1V For timing purposes as port pin is no longer floating when a 100 mV change from load voltage occurs and begins to float when a 100 mV change from the loaded VOH/VOL level occurs. IOL/IOH ≥ ± 20 mA. 25.3.12 Clock Waveforms Valid in normal clock mode. In X2 mode XTAL2 must be changed to XTAL2/2. 124 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 Figure 25-5. Internal Clock Signals INTERNAL CLOCK XTAL2 ALE EXTERNAL PROGRAM MEMORY FETCH PSEN P0 DATA SAMPLED FLOAT PCL OUT DATA SAMPLED FLOAT PCL OUT DATA SAMPLED FLOAT PCL OUT THESE SIGNALS ARE NOT ACTIVATED DURING THE EXECUTION OF A MOVX INSTRUCTION STATE4 P1 P2 STATE5 P1 P2 STATE6 P1 P2 STATE1 P1 P2 STATE2 P1 P2 STATE3 P1 P2 STATE4 P1 P2 STATE5 P1 P2 P2 (EXT) READ CYCLE RD INDICATES ADDRESS TRANSITIONS PCL OUT (IF PROGRAM MEMORY IS EXTERNAL) P0 DPL OR Rt OUT DATA SAMPLED FLOAT P2 WRITE CYCLE INDICATES DPH OR P2 SFR TO PCH TRANSITION WR P0 P2 DPL OR Rt OUT DATA OUT PCL OUT (EVEN IF PROGRAM MEMORY IS INTERNAL) PCL OUT (IF PROGRAM MEMORY IS EXTERNAL) INDICATES DPH OR P2 SFR TO PCH TRANSITION PORT OPERATION MOV PORT SRC MOV DEST P0 MOV DEST PORT (P1. P2. P3) (INCLUDES INTO. INT1. TO T1) SERIAL PORT SHIFT CLOCK TXD (MODE 0) P1, P2, P3 PINS SAMPLED P1, P2, P3 PINS SAMPLED OLD DATA NEW DATA P0 PINS SAMPLED P0 PINS SAMPLED RXD SAMPLED RXD SAMPLED This diagram indicates when signals are clocked internally. The time it takes the signals to propagate to the pins, however, ranges from 25 to 125 ns. This propagation delay is dependent on variables such as temperature and pin loading. Propagation also varies from output to output and component. Typically though (TA = 25°C fully loaded) RD and WR propagation delays are approximately 50 ns. The other signals are typically 85 ns. Propagation delays are incorporated in the AC specifications. 125 4235K–8051–05/08 26. Ordering Information Table 26-1. Part Number AT89C51RD2-SLSUM AT89C51RD2-RLTUM No AT89C51RD2-RDTUM(1) AT89C51RD2-SMSUM(1) 2.7V - 5.5V AT89C51ED2-SLSUM AT89C51ED2-RLTUM Yes AT89C51ED2- SMSUM AT89C51ED2-RDTUM PLCC68 VQFP64 Stick Tray AT89C51ED2-UM AT89C51ED2-UM Industrial & Green VQFP64 PLCC68 PLCC44 VQFP44 Tray Stick Stick Tray AT89C51RD2-UM AT89C51RD2-UM AT89C51ED2-UM AT89C51ED2-UM Possible Order Entries Data EEPROM Supply Voltage Temperature Range Package PLCC44 VQFP44 Packing Stick Tray Product Marking AT89C51RD2-UM AT89C51RD2-UM Note: 1. For PLCC68 and VQFP64 packages, please contact Atmel sales office for availability. 126 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 27. Packaging Information 27.1 PLCC44 127 4235K–8051–05/08 STANDARD NOTES FOR PLCC 1/ CONTROLLING DIMENSIONS : INCHES 2/ DIMENSIONING AND TOLERANCING PER ANSI Y 14.5M - 1982. 3/ "D" AND "E1" DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTUSIONS. MOLD FLASH OR PROTUSIONS SHALL NOT EXCEED 0.20 mm (.008 INCH) PER SIDE. 128 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 27.2 VQFP44 129 4235K–8051–05/08 STANDARD NOTES FOR PQFP/ VQFP / TQFP / DQFP 1/ CONTROLLING DIMENSIONS : INCHES 2/ ALL DIMENSIONING AND TOLERANCING CONFORM TO ANSI Y 14.5M 1982. 3/ "D1 AND E1" DIMENSIONS DO NOT INCLUDE MOLD PROTUSIONS. MOLD PROTUSIONS SHALL NOT EXCEED 0.25 mm (0.010 INCH). THE TOP PACKAGE BODY SIZE MAY BE SMALLER THAN THE BOTTOM PACKAGE BODY SIZE BY AS MUCH AS 0.15 mm. 4/ DATUM PLANE "H" LOCATED AT MOLD PARTING LINE AND COINCIDENT WITH LEAD, WHERE LEAD EXITS PLASTIC BODY AT BOTTOM OF PARTING LINE. 5/ DATUM "A" AND "D" TO BE DETERMINED AT DATUM PLANE H. 6/ DIMENSION " f " DOES NOT INCLUDE DAMBAR PROTUSION ALLOWABLE DAMBAR PROTUSION SHALL BE 0.08mm/.003" TOTAL IN EXCESS OF THE " f " DIMENSION AT MAXIMUM MATERIAL CONDITION . DAMBAR CANNOT BE LOCATED ON THE LOWER RADIUS OR THE FOOT. 130 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 27.3 PLCC68 131 4235K–8051–05/08 27.4 VQFP64 132 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 28. Document Revision History 28.1 Changes from 4235A -04/03 to 4135B - 06/03 1. VIH min changed from 0.2 VCC + 1.1 to 0.2 VCC + 0.9. 2. Added POR/PFD and reset specific sections. 3. Added DIL40 package. 4. Added Flash write programming time specification. 28.2 Changes from 4235B -06/03 to 4235C - 08/03 1. Changed maximum frequency to 60 MHz in X1 mode and 30 MHz in X2 mode for Vcc = 4.5V to 5.5V and internal code execution. 2. Added PDIL40 Packaging for AT89C51ED2. 28.3 Changes from 4235C - 08/03 to 4235D - 12/03 1. Improved explanations throughout the document. 28.4 Changes from 4235D - 12/03 to 4235E - 04/04 1. Improved explanations throughout the document. 28.5 Changes from 4235E - 04/04 to 4235F - 09/04 1. Improved explanations in Flash and EEPROM sections. 28.6 Changes from 4235F - 09/04 to 4235G 08/05 1. Added ‘Industrial & Green” product versions. 28.7 Changes from 4235G 08/05 to 4235H - 10/06 1. Correction to PDIL figure on page 9. 28.8 Changes from 4235H - 10/06 to 4235I - 04/07 1. Removal of PDIL40 package offering. 28.9 Changes from 4235I - 04/07 to 4235J - 01/08 1. Minor corrections throughout the document. 2. Updated Package drawings. 28.10 Changes from 4235J - 01/08 to 4235K - 05/08 1. Removed non-green packages from product ordering information. 133 4235K–8051–05/08 AT89C51RD2/ED2 Features .................................................................................................... 1 1 2 3 4 5 6 Description ............................................................................................... 2 Block Diagram .......................................................................................... 3 SFR Mapping ............................................................................................ 4 Pin Configurations ................................................................................... 9 Port Types .............................................................................................. 14 Oscillator ................................................................................................ 15 6.1 6.2 Registers .........................................................................................................15 Functional Block Diagram ................................................................................16 7 Enhanced Features ................................................................................ 17 7.1 X2 Feature .......................................................................................................17 8 9 Dual Data Pointer Register (DPTR) ...................................................... 21 Expanded RAM (XRAM) ......................................................................... 23 9.1 Registers .........................................................................................................24 10 Reset ....................................................................................................... 26 10.1 10.2 10.3 Introduction ......................................................................................................26 Reset Input ......................................................................................................26 Reset Output ...................................................................................................26 11 Power Monitor ........................................................................................ 28 11.1 Description .......................................................................................................28 12 Timer 2 .................................................................................................... 30 12.1 12.2 12.3 Auto-reload Mode ............................................................................................30 Programmable Clock-output ............................................................................31 Registers .........................................................................................................32 13 Programmable Counter Array (PCA) .................................................... 35 13.1 13.2 13.3 13.4 13.5 PCA Capture Mode .........................................................................................43 16-bit Software Timer/ Compare Mode ...........................................................43 High Speed Output Mode ................................................................................44 Pulse Width Modulator Mode ..........................................................................45 PCA Watchdog Timer ......................................................................................46 135 4235K–8051–05/08 14 Serial I/O Port ......................................................................................... 48 14.1 14.2 14.3 14.4 14.5 Framing Error Detection ..................................................................................48 Automatic Address Recognition ......................................................................49 Registers .........................................................................................................51 Baud Rate Selection for UART for Mode 1 and 3 ............................................51 UART Registers ...............................................................................................54 15 Keyboard Interface ................................................................................ 59 15.1 Registers .........................................................................................................60 16 Serial Port Interface (SPI) ...................................................................... 63 16.1 16.2 16.3 Features ..........................................................................................................63 Signal Description ............................................................................................63 Functional Description .....................................................................................65 17 Interrupt System .................................................................................... 72 17.1 17.2 Registers .........................................................................................................73 Interrupt Sources and Vector Addresses .........................................................73 18 Power Management ............................................................................... 80 18.1 18.2 18.3 18.4 Introduction ......................................................................................................80 Idle Mode .........................................................................................................80 Power-Down Mode ..........................................................................................81 Registers .........................................................................................................83 19 Hardware Watchdog Timer ................................................................... 84 19.1 19.2 Using the WDT ................................................................................................84 WDT during Power-down and Idle ...................................................................85 20 ONCE® Mode (ON- Chip Emulation) ..................................................... 86 21 Power-off Flag ........................................................................................ 87 22 Reduced EMI Mode ................................................................................ 88 23 EEPROM Data Memory .......................................................................... 89 23.1 23.2 23.3 Write Data ........................................................................................................89 Read Data .......................................................................................................90 Registers .........................................................................................................91 24 Flash/EEPROM Memory ........................................................................ 93 24.1 24.2 136 Features ..........................................................................................................93 Flash Programming and Erasure .....................................................................93 AT89C51RD2/ED2 4235K–8051–05/08 AT89C51RD2/ED2 24.3 24.4 24.5 24.6 24.7 24.8 24.9 24.10 Flash Registers and Memory Map ...................................................................94 Flash Memory Status....................................................................................... 97 Memory Organization ......................................................................................97 Bootloader Architecture ...................................................................................97 ISP Protocol Description ................................................................................102 Functional Description ...................................................................................103 Flow Description ............................................................................................104 API Call Description .......................................................................................112 25 Electrical Characteristics .................................................................... 114 25.1 25.2 25.3 Absolute Maximum Ratings ...........................................................................114 DC Parameters for Standard Voltage ............................................................114 AC Parameters ..............................................................................................117 26 Ordering Information ........................................................................... 126 27 Packaging Information ........................................................................ 127 27.1 27.2 27.3 27.4 PLCC44 .........................................................................................................127 VQFP44 .........................................................................................................129 PLCC68 .........................................................................................................131 VQFP64 .........................................................................................................132 28 Document Revision History ................................................................ 133 28.1 28.2 28.3 28.4 28.5 28.6 28.7 28.8 28.9 28.10 Changes from 4235A -04/03 to 4135B - 06/03 ..............................................133 Changes from 4235B -06/03 to 4235C - 08/03 ..............................................133 Changes from 4235C - 08/03 to 4235D - 12/03 ............................................133 Changes from 4235D - 12/03 to 4235E - 04/04 .............................................133 Changes from 4235E - 04/04 to 4235F - 09/04 .............................................133 Changes from 4235F - 09/04 to 4235G 08/05 ...............................................133 Changes from 4235G 08/05 to 4235H - 10/06 ..............................................133 Changes from 4235H - 10/06 to 4235I - 04/07 ..............................................133 Changes from 4235I - 04/07 to 4235J - 01/08 ...............................................133 Changes from 4235J - 01/08 to 4235K - 05/08 .............................................133 137 4235K–8051–05/08 Headquarters Atmel Corporation 2325 Orchard Parkway San Jose, CA 95131 USA Tel: 1(408) 441-0311 Fax: 1(408) 487-2600 International Atmel Asia Room 1219 Chinachem Golden Plaza 77 Mody Road Tsimshatsui East Kowloon Hong Kong Tel: (852) 2721-9778 Fax: (852) 2722-1369 Atmel Europe Le Krebs 8, Rue Jean-Pierre Timbaud BP 309 78054 Saint-Quentin-enYvelines Cedex France Tel: (33) 1-30-60-70-00 Fax: (33) 1-30-60-71-11 Atmel Japan 9F, Tonetsu Shinkawa Bldg. 1-24-8 Shinkawa Chuo-ku, Tokyo 104-0033 Japan Tel: (81) 3-3523-3551 Fax: (81) 3-3523-7581 Product Contact Web Site www.atmel.com Technical Support Enter Product Line E-mail Sales Contact www.atmel.com/contacts Literature Requests www.atmel.com/literature Disclaimer: T he information in this document is provided in connection with Atmel products. No license, express or implied, by estoppel or otherwise, to any intellectual property right is granted by this document or in connection with the sale of Atmel products. EXCEPT AS SET FORTH IN ATMEL’S TERMS AND CONDITIONS OF SALE LOCATED ON ATMEL’S WEB SITE, ATMEL ASSUMES NO LIABILITY WHATSOEVER AND DISCLAIMS ANY EXPRESS, IMPLIED OR STATUTORY WARRANTY RELATING TO ITS PRODUCTS INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT, CONSEQUENTIAL, PUNITIVE, SPECIAL OR INCIDENTAL DAMAGES (INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS OF PROFITS, BUSINESS INTERRUPTION, OR LOSS OF INFORMATION) ARISING OUT OF THE USE OR INABILITY TO USE THIS DOCUMENT, EVEN IF ATMEL HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. A tmel makes no representations or warranties with respect to the accuracy or completeness of the contents of this document and reserves the right to make changes to specifications and product descriptions at any time without notice. Atmel does not make any commitment to update the information contained herein. Unless specifically provided otherwise, Atmel products are not suitable for, and shall not be used in, automotive applications. Atmel’s products are not intended, authorized, or warranted for use as components in applications intended to support or sustain life. © 2007 Atmel Corporation. All rights reserved. A tmel ®, logo and combinations thereof, and others are registered trademarks or trademarks of Atmel Corporation or its subsidiaries. Other terms and product names may be trademarks of others. 4235K–8051–05/08