Features
• • • • • • • • • • • •
80C51 Core Architecture 256 Bytes of On-chip RAM 1 KB of On-chip XRAM 32 KB of On-chip Flash Memory – Data Retention: 10 Years at 85°C Read/Write Cycle: 10K 2 KB of On-chip Flash for Bootloader 2 KB of On-chip EEPROM Read/Write Cycle: 100K 14-sources 4-level Interrupts Three 16-bit Timers/Counters Full Duplex UART Compatible 80C51 Maximum Crystal Frequency 40 MHz, in X2 Mode, 20 MHz (CPU Core, 20 MHz) Five Ports: 32 + 2 Digital I/O Lines Five-channel 16-bit PCA with: – PWM (8-bit) – High-speed Output – Timer and Edge Capture Double Data Pointer 21-bit Watchdog Timer (7 Programmable Bits) 10-bit Resolution Analog to Digital Converter (ADC) with 8 Multiplexed Inputs On-chip Emulation Logic (Enhanced Hook System) Power Saving Modes: – Idle Mode – Power-down Mode Power Supply: 3V to 5.5V Temperature Range: Industrial (-40 ° to +85°C) Packages: VQFP44, PLCC44
Enhanced 8-bit Microcontroller with 32 KB Flash Memory
• • • • • • • •
AT89C51AC2 T89C51AC2
Description
The A/T89C51AC2 is a high performance Flash version of the 80C51 single chip 8-bit microcontrollers. It contains a 32 KB Flash memory block for program and data. The 32 KB 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 A/T89C51AC2 retains all features of the 80C51 with 256 bytes of internal RAM, a 7-source 4-level interrupt controller and three timer/counters. In addition, the A/T89C51AC2 has a 10-bit A/D converter, a 2 KB Boot Flash memory, 2 KB EEPROM for data, a Programmable Counter Array, an XRAM of 1024 bytes, a Hardware WatchDog Timer, and a more versatile serial channel that facilitates multiprocessor communication (EUART). The fully static design of the A/T89C51AC2 reduces system power consumption by bringing the clock frequency down to any value, even DC, without loss of data. The A/T89C51AC2 has two software-selectable modes of reduced activity and an 8bit 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 A/T89C51AC2 make it more powerful for applications that need A/D conversion, pulse width modulation, high speed I/O and counting capabilities such as industrial control, consumer goods, alarms, motor control, among others. While remaining fully compatible with the 80C52, the T8C51AC2 offers a superset of this standard microcontroller. In X2 mode, a maximum external clock rate of 20 MHz reaches a 300 ns cycle time.
Rev. 4127G–8051–05/06
1
Block Diagram
T2EX VAVCC VAREF RxD TxD Vcc Vss PCA ECI T2 VAGND
XTAL1 XTAL2 ALE PSEN CPU EA RD WR Timer 0 Timer 1 INT Ctrl Parallel I/O Ports and Ext. Bus Watch Dog Port 0 Port 1 Port 2 Port 3 Port 4 10 bit ADC UART RAM 256x8
C51 CORE
Flash Boot EE 32kx loader PROM 8 2kx8 2kx8
XRAM
1kx8
PCA
Timer 2
IB-bus
P1 (1)
RESET
INT0
Notes:
1. 8 analog Inputs/8 Digital I/O 2. 2-Bit I/O Port
2
A/T89C51AC2
4127G–8051–05/06
INT1
P4(2)
P2
T0
T1
P0
P3
A/T89C51AC2
Pin Configuration
P1.3/AN3/CEX0 P1.2/AN2/ECI P1.1/AN1/T2EX P1.0/AN 0/T2 VAREF VAGND RESET VSS VCC XTAL1 XTAL2 P1.4/AN4/CEX1 P1.5/AN5/CEX2 P1.6/AN6/CEX3 P1.7/AN7/CEX4 EA P3.0/RxD 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 6 5 4 3 2 1 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29
PLCC44
ALE PSEN P0.7/AD7 P0.6/AD6 P0.5/AD5 P0.4/AD4 P0.3/AD3 P0.2/AD2 P0.1/AD1 P0.0/AD0 P2.0/A8
44 43 42 41 40 39 38 37 36 35 34
P1.3/AN3/CEX0 P1.2/AN2/ECI P1.1/AN1/T2EX P1.0/AN 0/T2 VAREF VAGND RESET VSS VCC XTAL1 XTAL2
P3.6/WR P3.7/RD P4.0 P4.1 P2.7/A15 P2.6/A14 P2.5/A13 P2.4/A12 P2.3/A11 P2.2/A10 P2.1/A9
18 19 20 21 22 23 24 25 26 27 28
P1.4/AN4/CEX1 P1.5/AN5/CEX2 P1.6/AN6/CEX3 P1.7/AN7/CEX4 EA P3.0/RxD P3.1/TxD P3.2/INT0 P3.3/INT1 P3.4/T0 P3.5/T1
1 2 3 4 5 6 7 8 9 10 11
33 32 31 30 29 28 27 26 25 24 23
VQFP44
ALE PSEN P0.7/AD7 P0.6/AD6 P0.5/AD5 P0.4 /AD4 P0.3 /AD3 P0.2 /AD2 P0.1 /AD1 P0.0 /AD0 P2.0/A8
12 13 14 15 16 17 18 19 20 21 22
P3.6/WR P3.7/RD P4.0 P4.1 P2.7/A15 P2.6/A14 P2.5/A13 P2.4/A12 P2.3/A11 P2.2/A10 P2.1/A9
3
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Table 1. Pin Description
Pin Name VSS VCC VAREF VAGND P0.0:7 I/O Type GND Description Circuit ground Supply Voltage Reference Voltage for ADC Reference Ground for ADC Port 0: Is an 8-bit open drain bi-directional I/O port. Port 0 pins that have 1’s written to them float, and in this state can be used as high-impedance inputs. Port 0 is also the multiplexed low-order address and data bus during accesses to external Program and Data Memory. In this application it uses strong internal pull-ups when emitting 1’s. Port 0 also outputs the code Bytes during program validation. External pull-ups are required during program verification. Port 1: Is an 8-bit bi-directional I/O port with internal pull-ups. Port 1 pins can be used for digital input/output or as analog inputs for the Analog Digital Converter (ADC). Port 1 pins that have 1’s written to them are pulled high by the internal pull-up transistors and can be used as inputs in this state. As inputs, Port 1 pins that are being pulled low externally will be the source of current (IIL, see section "Electrical Characteristic") because of the internal pull-ups. Port 1 pins are assigned to be used as analog inputs via the ADCCF register (in this case the internal pull-ups are disconnected). As a secondary digital function, port 1 contains the Timer 2 external trigger and clock input; the PCA external clock input and the PCA module I/O. P1.0/AN0/T2 Analog input channel 0, External clock input for Timer/counter2. P1.1/AN1/T2EX Analog input channel 1, Trigger input for Timer/counter2. P1.2/AN2/ECI Analog input channel 2, PCA external clock input. P1.3/AN3/CEX0 Analog input channel 3, PCA module 0 Entry of input/PWM output. P1.4/AN4/CEX1 Analog input channel 4, PCA module 1 Entry of input/PWM output. P1.5/AN5/CEX2 Analog input channel 5, PCA module 2 Entry of input/PWM output. P1.6/AN6/CEX3 Analog input channel 6, PCA module 3 Entry of input/PWM output. P1.7/AN7/CEX4 Analog input channel 7, PCA module 4 Entry ot input/PWM output. Port 1 receives the low-order address byte during EPROM programming and program verification. It can drive CMOS inputs without external pull-ups. P2.0:7 I/O Port 2: Is an 8-bit bi-directional I/O port with internal pull-ups. Port 2 pins that have 1’s written to them are pulled high by the internal pull-ups and can be used as inputs in this state. As inputs, Port 2 pins that are being pulled low externally will be a source of current (IIL, see section "Electrical Characteristic") because of the internal pull-ups. Port 2 emits the high-order address byte during accesses to the external Program Memory and during accesses to external Data Memory that uses 16-bit addresses (MOVX @DPTR). In this application, it uses strong internal pull-ups when emitting 1’s. During accesses to external Data Memory that use 8 bit addresses (MOVX @Ri), Port 2 transmits the contents of the P2 special function register. It also receives high-order addresses and control signals during program validation. It can drive CMOS inputs without external pull-ups.
P1.0:7
I/O
4
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A/T89C51AC2
Table 1. Pin Description (Continued)
Pin Name P3.0:7 Type I/O Description Port 3: Is an 8-bit bi-directional I/O port with internal pull-ups. Port 3 pins that have 1’s written to them are pulled high by the internal pull-up transistors and can be used as inputs in this state. As inputs, Port 3 pins that are being pulled low externally will be a source of current (IIL , see section "Electrical Characteristic") because of the internal pull-ups. The output latch corresponding to a secondary function must be programmed to one for that function to operate (except for TxD and WR). The secondary functions are assigned to the pins of port 3 as follows: P3.0/RxD: Receiver data input (asynchronous) or data input/output (synchronous) of the serial interface P3.1/TxD: Transmitter data output (asynchronous) or clock output (synchronous) of the serial interface P3.2/INT0: External interrupt 0 input/timer 0 gate control input P3.3/INT1: External interrupt 1 input/timer 1 gate control input P3.4/T0: Timer 0 counter input P3.5/T1: Timer 1 counter input P3.6/WR: External Data Memory write strobe; latches the data byte from port 0 into the external data memory P3.7/RD: External Data Memory read strobe; Enables the external data memory. It can drive CMOS inputs without external pull-ups. P4.0:1 I/O Port 4: Is an 2-bit bi-directional I/O port with internal pull-ups. Port 4 pins that have 1’s written to them are pulled high by the internal pull-ups and can be used as inputs in this state. As inputs, Port 4 pins that are being pulled low externally will be a source of current (IIL, on the datasheet) because of the internal pull-up transistor. P4.0 P4.1: It can drive CMOS inputs without external pull-ups. Reset: A high level on this pin during two machine cycles while the oscillator is running resets the device. An internal pull-down resistor to VSS permits power-on reset using only an external capacitor to VCC. ALE: An Address Latch Enable output for latching the low byte of the address during accesses to the external memory. The ALE is activated every 1/6 oscillator periods (1/3 in X2 mode) except during an external data memory access. When instructions are executed from an internal Flash (EA = 1), ALE generation can be disabled by the software. PSEN: The Program Store Enable output is a control signal that enables the external program memory of the bus during external fetch operations. It is activated twice each machine cycle during fetches from the external program memory. However, when executing from of the external program memory two activations of PSEN are skipped during each access to the external Data memory. The PSEN is not activated for internal fetches. EA: When External Access is held at the high level, instructions are fetched from the internal Flash when the program counter is less then 8000H. When held at the low level,A/T89C51AC2 fetches all instructions from the external program memory. XTAL1: Input of the inverting oscillator amplifier and input of the internal clock generator circuits. To drive the device from an external clock source, XTAL1 should be driven, while XTAL2 is left unconnected. To operate above a frequency of 16 MHz, a duty cycle of 50% should be maintained. XTAL2: Output from the inverting oscillator amplifier.
RESET
I/O
ALE
O
PSEN
O
EA
I
XTAL1
I
XTAL2
O
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4127G–8051–05/06
I/O Configurations
Each Port SFR operates via type-D latches, as illustrated in Figure 1 for Ports 3 and 4. A CPU "write to latch" signal initiates transfer of internal bus data into the type-D latch. A CPU "read latch" signal transfers the latched Q output onto the internal bus. Similarly, a "read pin" signal transfers the logical level of the Port pin. Some Port data instructions activate the "read latch" signal while others activate the "read pin" signal. Latch instructions are referred to as Read-Modify-Write instructions. Each I/O line may be independently programmed as input or output.
Port 1, Port 3 and Port 4
Figure 1 shows the structure of Ports 1 and 3, which have internal pull-ups. An external source can pull the pin low. Each Port pin can be configured either for general-purpose I/O or for its alternate input output function. To use a pin for general-purpose output, set or clear the corresponding bit in the Px register (x = 1,3 or 4). To use a pin for general-purpose input, set the bit in the Px register. This turns off the output FET drive. To configure a pin for its alternate function, set the bit in the Px register. When the latch is set, the "alternate output function" signal controls the output level (see Figure 1). The operation of Ports 1, 3 and 4 is discussed further in the "quasi-Bidirectional Port Operation" section. Figure 1. Port 1, Port 3 and Port 4 Structure
VCC ALTERNATE OUTPUT FUNCTION
INTERNAL PULL-UP (1)
READ LATCH
INTERNAL BUS WRITE TO LATCH
D P1.X Q P3.X P4.X LATCH CL
P1.x P3.x P4.x
READ PIN
ALTERNATE INPUT FUNCTION
Note:
The internal pull-up can be disabled on P1 when analog function is selected.
Port 0 and Port 2
Ports 0 and 2 are used for general-purpose I/O or as the external address/data bus. Port 0, shown in Figure 3, differs from the other Ports in not having internal pull-ups. Figure 3 shows the structure of Port 2. An external source can pull a Port 2 pin low. To use a pin for general-purpose output, set or clear the corresponding bit in the Px register (x = 0 or 2). To use a pin for general-purpose input, set the bit in the Px register to turn off the output driver FET.
6
A/T89C51AC2
4127G–8051–05/06
A/T89C51AC2
Figure 2. Port 0 Structure
ADDRESS LOW/ CONTROL DATA VDD
READ LATCH
1
(2) P0.x (1)
INTERNAL BUS WRITE TO LATCH
D
P0.X LATCH
Q
0
READ PIN
Notes:
1. Port 0 is precluded from use as general-purpose I/O Ports when used as address/data bus drivers. 2. Port 0 internal strong pull-ups assist the logic-one output for memory bus cycles only. Except for these bus cycles, the pull-up FET is off, Port 0 outputs are open-drain.
Figure 3. Port 2 Structure
ADDRESS HIGH/ CONTROL VDD INTERNAL PULL-UP (2)
READ LATCH
1
P2.x (1)
INTERNAL BUS WRITE TO LATCH D Q
0
P2.X LATCH
READ PIN
Notes:
1. Port 2 is precluded from use as general-purpose I/O Ports when as address/data bus drivers. 2. Port 2 internal strong pull-ups FET (P1 in FiGURE) assist the logic-one output for memory bus cycle.
When Port 0 and Port 2 are used for an external memory cycle, an internal control signal switches the output-driver input from the latch output to the internal address/data line.
Read-Modify-Write Instructions
Some instructions read the latch data rather than the pin data. The latch based instructions read the data, modify the data and then rewrite the latch. These are called "ReadModify-Write" instructions. Below is a complete list of these special instructions (see Table ). When the destination operand is a Port or a Port bit, these instructions read the latch rather than the pin:
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4127G–8051–05/06
Table 2. R ead-Modify-Write Instructions
Instruction ANL ORL XRL JBC CPL INC DEC DJNZ MOV Px.y, C CLR Px.y SET Px.y Description logical AND logical OR logical EX-OR jump if bit = 1 and clear bit complement bit increment decrement decrement and jump if not zero move carry bit to bit y of Port x clear bit y of Port x set bit y of Port x Example ANL P1, A ORL P2, A XRL P3, A JBC P1.1, LABEL CPL P3.0 INC P2 DEC P2 DJNZ P3, LABEL MOV P1.5, C CLR P2.4 SET P3.3
It is not obvious the last three instructions in this list are Read-Modify-Write instructions. These instructions read the port (all 8 bits), modify the specifically addressed bit and write the new byte back to the latch. These Read-Modify-Write instructions are directed to the latch rather than the pin in order to avoid possible misinterpretation of voltage (and therefore, logic) levels at the pin. For example, a Port bit used to drive the base of an external bipolar transistor can not rise above the transistor’s base-emitter junction voltage (a value lower than VIL). With a logic one written to the bit, attempts by the CPU to read the Port at the pin are misinterpreted as logic zero. A read of the latch rather than the pins returns the correct logic-one value.
Quasi-Bidirectional Port Operation
Port 1, Port 2, Port 3 and Port 4 have fixed internal pull-ups and are referred to as "quasi-bidirectional" Ports. When configured as an input, the pin impedance appears as logic one and sources current in response to an external logic zero condition. Port 0 is a "true bidirectional" pin. The pins float when configured as input. Resets write logic one to all Port latches. If logical zero is subsequently written to a Port latch, it can be returned to input conditions by a logical one written to the latch.
Note: Port latch values change near the end of Read-Modify-Write instruction cycles. Output buffers (and therefore the pin state) update early in the instruction after Read-ModifyWrite instruction cycle.
Logical zero-to-one transitions in Port 1, Port 2, Port 3 and Port 4 use an additional pullup (p1) to aid this logic transition (see Figure 4.). This increases switch speed. This extra pull-up sources 100 times normal internal circuit current during 2 oscillator clock periods. The internal pull-ups are field-effect transistors rather than linear resistors. Pullups consist of three p-channel FET (pFET) devices. A pFET is on when the gate senses logical zero and off when the gate senses logical one. pFET #1 is turned on for two oscillator periods immediately after a zero-to-one transition in the Port latch. A logical one at the Port pin turns on pFET #3 (a weak pull-up) through the inverter. This inverter and pFET pair form a latch to drive logical one. pFET #2 is a very weak pull-up switched on whenever the associated nFET is switched off. This is traditional CMOS switch convention. Current strengths are 1/10 that of pFET #3.
8
A/T89C51AC2
4127G–8051–05/06
A/T89C51AC2
Figure 4. Internal Pull-Up Configurations
2 Osc. PERIODS VCC p1(1) VCC p2 VCC p3 P1.x P2.x P3.x P4.x OUTPUT DATA n
INPUT DATA READ PIN
Note:
Port 2 p1 assists the logic-one output for memory bus cycles.
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4127G–8051–05/06
SFR Mapping
The Special Function Registers (SFRs) of the A/T89C51AC2 fall into the following categories:
Table 3. C51 Core SFRs
Mnemonic ACC B PSW SP Add Name 7 – – CY – 6 – – AC – 5 – – F0 – 4 – – RS1 – 3 – – RS0 – 2 – – OV – 1 – – F1 – 0 – – P –
E0h Accumulator F0h B Register D0h Program Status Word 81h Stack Pointer Data Pointer Low 82h byte LSB of DPTR Data Pointer High 83h byte MSB of DPTR
DPL
–
–
–
–
–
–
–
–
DPH
–
–
–
–
–
–
–
–
Table 4. I/O Port SFRs
Mnemonic P0 P1 P2 P3 P4 Add Name 7 – – – – – 6 – – – – – 5 – – – – – 4 – – – – – 3 – – – – – 2 – – – – – 1 – – – – – 0 – – – – –
80h Port 0 90h Port 1 A0h Port 2 B0h Port 3 C0h Port 4 (x2)
Table 5. Timers SFRs
Mnemonic TH0 Add 8Ch Name Timer/Counter 0 High byte Timer/Counter 0 Low byte Timer/Counter 1 High byte Timer/Counter 1 Low byte Timer/Counter 2 High byte Timer/Counter 2 Low byte Timer/Counter 0 and 1 control Timer/Counter 0 and 1 Modes 7 – 6 – 5 – 4 – 3 – 2 – 1 – 0 –
TL0
8Ah
–
–
–
–
–
–
–
–
TH1
8Dh
–
–
–
–
–
–
–
–
TL1
8Bh
–
–
–
–
–
–
–
–
TH2
CDh
–
–
–
–
–
–
–
–
TL2
CCh
–
–
–
–
–
–
–
–
TCON
88h
TF1
TR1
TF0
TR0
IE1
IT1
IE0
IT0
TMOD
89h
GATE1
C/T1#
M11
M01
GATE0
C/T0#
M10
M00
10
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A/T89C51AC2
Table 5. Timers SFRs (Continued)
Mnemonic T2CON Add C8h Name Timer/Counter 2 control Timer/Counter 2 Mode 7 TF2 6 EXF2 5 RCLK 4 TCLK 3 EXEN2 2 TR2 1 C/T2# 0 CP/RL2#
T2MOD
C9h
–
–
–
–
–
–
T2OE
DCEN
RCAP2H
Timer/Counter 2 CBh Reload/Capture High byte Timer/Counter 2 CAh Reload/Capture Low byte A6h Watchdog Timer Reset Watchdog Timer Program
–
–
–
–
–
–
–
–
RCAP2L
–
–
–
–
–
–
–
–
WDTRST
–
–
–
–
–
–
–
–
WDTPRG
A7h
–
–
–
–
–
S2
S1
S0
Table 6. Serial I/O Port SFRs
Mnemonic SCON SBUF SADEN SADDR Add Name 7 FE/SM0 – – – 6 SM1 – – – 5 SM2 – – – 4 REN – – – 3 TB8 – – – 2 RB8 – – – 1 TI – – – 0 RI – – –
98h Serial Control 99h Serial Data Buffer B9h Slave Address Mask A9h Slave Address
Table 7. PCA SFRs
Mnemonic Add
Name CF
7 CR
6
5 – – – – CAPP0 CAPP1 CAPP2 CAPP3 CAPP4
4 CCF4 – – – CAPN0 CAPN1 CAPN2 CAPN3 CAPN4
3 CCF3 – – – MAT0 MAT1 MAT2 MAT3 MAT4
2 CCF2 CPS1 – – TOG0 TOG1 TOG2 TOG3 TOG4
1 CCF1 CPS0 – – PWM0 PWM1 PWM2 PWM3 PWM4
0 CCF0 ECF – – ECCF0 ECCF1 ECCF2 ECCF3 ECCF4
CCON CMOD CL CH CCAPM0 CCAPM1 CCAPM2 CCAPM3 CCAPM4 CCAP0H CCAP1H CCAP2H CCAP3H CCAP4H
D8h PCA Timer/Counter Control D9h PCA Timer/Counter Mode E9h PCA Timer/Counter Low byte F9h PCA Timer/Counter High byte DAh PCA Timer/Counter Mode 0 DBh PCA Timer/Counter Mode 1 DCh PCA Timer/Counter Mode 2 DDh PCA Timer/Counter Mode 3 DEh PCA Timer/Counter Mode 4
CIDL – –
WDTE – – ECOM0 ECOM1
–
ECOM2 ECOM3 ECOM4
FAh PCA Compare Capture Module 0 H CCAP0H7 CCAP0H6 CCAP0H5 CCAP0H4 CCAP0H3 CCAP0H2 CCAP0H1 CCAP0H0 FBh PCA Compare Capture Module 1 H CCAP1H7 CCAP1H6 CCAP1H5 CCAP1H4 CCAP1H3 CCAP1H2 CCAP1H1 CCAP1H0 FCh PCA Compare Capture Module 2 H CCAP2H7 CCAP2H6 CCAP2H5 CCAP2H4 CCAP2H3 CCAP2H2 CCAP2H1 CCAP2H0 FDh PCA Compare Capture Module 3 H CCAP3H7 CCAP3H6 CCAP3H5 CCAP3H4 CCAP3H3 CCAP3H2 CCAP3H1 CCAP3H0 FEh PCA Compare Capture Module 4 H CCAP4H7 CCAP4H6 CCAP4H5 CCAP4H4 CCAP4H3 CCAP4H2 CCAP4H1 CCAP4H0
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Table 7. PCA SFRs (Continued)
Mnemonic Add
Name
7
6
5
4
3
2
1
0
CCAP0L CCAP1L CCAP2L CCAP3L CCAP4L
EAh EBh ECh EDh EEh
PCA Compare Capture Module 0 L CCAP0L7 CCAP0L6 CCAP0L5 CCAP0L4 CCAP0L3 CCAP0L2 CCAP0L1 CCAP0L0 PCA Compare Capture Module 1 L CCAP1L7 CCAP1L6 CCAP1L5 CCAP1L4 CCAP1L3 CCAP1L2 CCAP1L1 CCAP1L0 PCA Compare Capture Module 2 L CCAP2L7 CCAP2L6 CCAP2L5 CCAP2L4 CCAP2L3 CCAP2L2 CCAP2L1 CCAP2L0 PCA Compare Capture Module 3 L CCAP3L7 CCAP3L6 CCAP3L5 CCAP3L4 CCAP3L3 CCAP3L2 CCAP3L1 CCAP3L0 PCA Compare Capture Module 4 L CCAP4L7 CCAP4L6 CCAP4L5 CCAP4L4 CCAP4L3 CCAP4L2 CCAP4L1 CCAP4L0
Table 8. Interrupt SFRs
Mnemonic IEN0 Add A8h Name Interrupt Enable Control 0 Interrupt Enable Control 1 Interrupt Priority Control Low 0 Interrupt Priority Control High 0 Interrupt Priority Control Low 1 Interrupt Priority Control High1 7 EA 6 EC 5 ET2 4 ES 3 ET1 2 EX1 1 ET0 0 EX0
IEN1
E8h
–
–
–
–
–
–
EADC
–
IPL0
B8h
–
PPC
PT2
PS
PT1
PX1
PT0
PX0
IPH0
B7h
–
PPCH
PT2H
PSH
PT1H
PX1H
PT0H
PX0H
IPL1
F8h
–
–
–
–
–
–
PADCL
–
IPH1
F7h
–
–
–
–
–
–
PADCH
–
Table 9. ADC SFRs
Mnemonic ADCON ADCF ADCLK ADDH ADDL Add Name 7 – CH7 – ADAT9 – 6 PSIDLE CH6 – ADAT8 – 5 ADEN CH5 – ADAT7 – 4 ADEOC CH4 PRS4 ADAT6 – 3 ADSST CH3 PRS3 ADAT5 – 2 SCH2 CH2 PRS2 ADAT4 – 1 SCH1 CH1 PRS1 ADAT3 ADAT1 0 SCH0 CH0 PRS0 ADAT2 ADAT0
F3h ADC Control F6h ADC Configuration F2h ADC Clock F5h ADC Data High byte F4h ADC Data Low byte
Table 10. Other SFRs
Mnemonic PCON AUXR AUXR1 CKCON FCON EECON Add 87h 8Eh A2h 8Fh D1h D2h Name Power Control Auxiliary Register 0 Auxiliary Register 1 Clock Control Flash Control EEPROM Contol 7 SMOD1 – – – FPL3 EEPL3 6 SMOD0 – – WDX2 FPL2 EEPL2 5 – M0 ENBOOT PCAX2 FPL1 EEPL1 4 POF – – SIX2 FPL0 EEPL0 3 GF1 XRS1 GF3 T2X2 FPS – 2 GF0 XRS2 0 T1X2 FMOD1 – 1 PD EXTRAM – T0X2 FMOD0 EEE 0 IDL A0 DPS X2 FBUSY EEBUSY
12
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A/T89C51AC2
Table 11. SFR Mapping
0/8 (1) F8h IPL1 xxxx xx0x B 0000 0000 IEN1 xxxx xx0x ACC 0000 0000 CCON 00x0 0000 PSW 0000 0000 T2CON 0000 0000 P4 xxxx xx11 IPL0 x000 0000 P3 1111 1111 IEN0 0000 0000 P2 1111 1111 SCON 0000 0000 P1 1111 1111 TCON 0000 0000 P0 1111 1111 0/8 (1) 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 x00x 1100 CKCON 0000 0000 PCON 00x1 0000 7/F SBUF 0000 0000 SADDR 0000 0000 AUXR1 xxxx 00x0 WDTRST 1111 1111 WDTPRG xxxx x000 SADEN 0000 0000 IPH0 x000 0000 CMOD 00xx x000 FCON 0000 0000 T2MOD xxxx xx00 CCAPM0 x000 0000 EECON xxxx xx00 RCAP2L 0000 0000 RCAP2H 0000 0000 TL2 0000 0000 TH2 0000 0000 CCAPM1 x000 0000 CCAPM2 x000 0000 CCAPM3 x000 0000 CCAPM4 x000 0000 CL 0000 0000 1/9 CH 0000 0000 2/A CCAP0H 0000 0000 ADCLK xxx0 0000 CCAP0L 0000 0000 3/B CCAP1H 0000 0000 ADCON x000 0000 CCAP1L 0000 0000 4/C CCAP2H 0000 0000 ADDL 0000 0000 CCAP2L 0000 0000 5/D CCAP3H 0000 0000 ADDH 0000 0000 CCAP3L 0000 0000 6/E CCAP4H 0000 0000 ADCF 0000 0000 CCAP4L 0000 0000 IPH1 xxxx xx0x 7/F FFh
F0h
F7h
E8h
EFh
E0h
E7h
D8h
DFh
D0h
D7h
C8h
CFh
C0h
C7h
B8h
BFh
B0h
B7h
A8h
AFh
A0h
A7h
98h
9Fh
90h
97h
88h
8Fh
80h
87h
Reserved
Note: 1. These registers are bit–addressable. Sixteen addresses in the SFR space are both byte–addressable and bit–addressable. The bit–addressable SFR’s are those whose address ends in 0 and 8. The bit addresses, in this area, are 0x80 through to 0xFF.
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Clock
The A/T89C51AC2 core needs only 6 clock periods per machine cycle. This feature, called ”X2”, provides the following advantages: • • • • Divides frequency crystals by 2 (cheaper crystals) while keeping the same CPU power. Saves power consumption while keeping the same CPU power (oscillator power saving). Saves power consumption by dividing dynamic operating frequency by 2 in operating and idle modes. Increases CPU power by 2 while keeping the 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 the software. An extra feature is available to start after Reset in the X2 mode. This feature can be enabled by a bit X2B in the Hardware Security Byte. This bit is described in the section "In-System-Programming".
Description
The X2 bit in the CKCON register (see Table 12) allows switching from 12 clock cycles per instruction to 6 clock cycles and vice versa. At reset, the standard speed is activated (STD mode). Setting this bit activates the X2 feature (X2 mode) for the CPU Clock only (see Figure 5.). The Timers 0, 1 and 2, Uart, PCA, or Watchdog switch in X2 mode only if the corresponding bit is cleared in the CKCON register. The clock for the whole circuit and peripheral is first divided by two before being used by the CPU core and peripherals. This allows any cyclic ratio to be accepted on the XTAL1 input. In X2 mode, as this divider is bypassed, the signals on XTAL1 must have a cyclic ratio between 40 to 60%. Figure 5. shows the clock generation block diagram. The X2 bit is validated on the XTAL1÷2 rising edge to avoid glitches when switching from the X2 to the STD mode. Figure 6 shows the mode switching waveforms.
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Figure 5. Clock CPU Generation Diagram
X2B
Hardware byte On RESET PCON.0
IDL
X2
CKCON.0
XTAL1
÷2
0 1
CPU Core Clock
XTAL2
CPU CLOCK
PD
PCON.1
CPU Core Clock Symbol and ADC
1 2
÷ ÷ ÷ ÷ ÷ ÷
FT0 Clock
X2
CKCON.0
WDX2
CKCON.6
PCAX2
CKCON.5
SIX2
CKCON.4
T2X2
CKCON.3
T1X2
CKCON.2
T0X2
CKCON.1
4127G–8051–05/06
0 1 0 2
FT1 Clock
1 0
2
FT2 Clock FUart Clock
1 0
2
1 0
2
FPca Clock FWd Clock
1 0
2
PERIPH CLOCK
Peripheral Clock Symbol
15
Figure 6. Mode Switching Waveforms
XTAL1
XTAL1/2
X2 bit
CPU clock STD Mode X2 Mode STD Mode
Note:
In order to prevent any incorrect operation while operating in the X2 mode, users must be aware that all peripherals using the clock frequency as a time reference (UART, timers...) will have their time reference divided by two. For example a free running timer generating an interrupt every 20 ms will then generate an interrupt every 10 ms. A UART with a 4800 baud rate will have a 9600 baud rate.
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Register
Table 12. CKCON Register CKCON (S:8Fh) Clock Control Register
7 Bit Number 6 WDX2 5 PCAX2 4 SIX2 3 T2X2 2 T1X2 1 T0X2 0 X2
Bit Mnemonic Description Reserved Do not set this bit. Watchdog clock (1) Clear to select 6 clock periods per peripheral clock cycle. Set to select 12 clock periods per peripheral clock cycle. Programmable Counter Array clock (1) Clear 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) (1) Clear to select 6 clock periods per peripheral clock cycle. Set to select 12 clock periods per peripheral clock cycle. Timer 2 clock (1) Clear to select 6 clock periods per peripheral clock cycle. Set to select 12 clock periods per peripheral clock cycle. Timer 1 clock (1) Clear to select 6 clock periods per peripheral clock cycle. Set to select 12 clock periods per peripheral clock cycle. Timer 0 clock (1) Clear to select 6 clock periods per peripheral clock cycle. Set to select 12 clock periods per peripheral clock cycle. CPU clock Clear 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.
6
WDX2
5
PCAX2
4
SIX2
3
T2X2
2
T1X2
1
T0X2
0
X2
Note:
1. This control bit is validated when the CPU clock bit X2 is set; when X2 is low, this bit has no effect.
Reset Value = x000 0000b
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Power Management
Two power reduction modes are implemented in the A/T89C51AC2: 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 “Clock”. In order to start-up (cold reset) or to restart (warm reset) properly the microcontroller, a high level has to be applied on the RST pin. A bad level leads to a wrong initialisation of the internal registers like SFRs, PC, etc. and to unpredictable behavior of the microcontroller. A warm reset can be applied either directly on the RST pin or indirectly by an internal reset source such as a watchdog, PCA, timer, etc.
Reset Pin
At Power-up (Cold Reset) Two conditions are required before enabling a CPU start-up:
• • VDD must reach the specified VDD range, The level on xtal1 input must be outside the specification (VIH, VIL).
If one of these two conditions are not met, the microcontroller does not start correctly and can execute an instruction fetch from anywhere in the program space. An active level applied on the RST pin must be maintained until both of the above conditions are met. A reset is active when the level VIH1 is reached and when the pulse width covers the period of time where VDD and the oscillator are not stabilized. Two parameters have to be taken into account to determine the reset pulse width: • • VDD rise time (vddrst), Oscillator startup time (oscrst).
To determine the capacitor the highest value of these two parameters has to be chosen. The reset circuitry is shown in Figure 7. Figure 7. Reset Circuitry
VDD Crst RST pin Internal reset Rrst Reset input circuitry
0
Table 13 and Table 15 give some typical examples for three values of VDD rise times, two values of oscillator start-up time and two pull-down resistor values. Table 13. Minimum Reset Capacitor for a 15k Pull-down Resistor
oscrst/vddrst 5 ms 20 ms 1ms 2.7 µF 10 µF 10ms 4.7 µF 15 µF 100ms 47 µF 47 µF
Note:
These values assume VDD starts from 0v to the nominal value. If the time between two on/off sequences is too fast, the power-supply de coupling capacitors may not be fully discharged, leading to a bad reset sequence.
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Warm Reset To achieve a valid reset, the reset signal must be maintained for at least 2 machine cycles (24 oscillator clock periods) while the oscillator is running. The number of clock periods is mode independent (X2 or X1). As detailed in Section “PCA Watchdog Timer”, page 80, 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 1KΩ resistor must be added as shown Figure 8. Figure 8. Reset Circuitry for WDT reset out usage
VDD
Watchdog Reset
+
RST
VDD
1K RRST
To CPU core and peripherals
RST
VSS
VSS
To other on-board circuitry
Reset Recommendation to Prevent Flash Corruption
An example of bad initialization situation may occur in an instance where the bit ENBOOT in AUXR1 register is initialized from the hardware bit BLJB upon reset. Since this bit allows mapping of the bootloader in the code area, a reset failure can be critical. If one wants the ENBOOT cleared in order to unmap the boot from the code area (yet due to a bad reset) the bit ENBOOT in SFRs may be set. If the value of Program Counter is accidently in the range of the boot memory addresses then a flash access (write or erase) may corrupt the Flash on-chip memory. It is recommended to use an external reset circuitry featuring power supply monitoring to prevent system malfunction during periods of insufficient power supply voltage (power supply failure, power supply switched off).
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 14. To enter Idle mode, you must set the IDL bit in PCON register (see Table 15). The T89C51CC02 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 T89C51CC02 enters Power-down mode. Then it does not go in Idle mode when exiting Power-down mode.
Entering Idle Mode
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.
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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 T89C51CC02 and vectors the CPU to address C:0000h.
1. 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. 2. If Idle mode is invoked by ADC Idle, the ADC conversion completion will exit Idle.
Notes:
Power-down Mode
The Power-down mode places the T89C51CC02 in a very low power state. Power-down mode stops the oscillator and freezes all clocks 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 SFRs and RAM contents are preserved. The status of the Port pins during Power-down mode is detailed in Table 14. To enter Power-down mode, set PD bit in PCON register. The T89C51CC02 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. If VDD was reduced during the Power-down mode, do not exit Power-down mode until VDD is restored to the normal operating level. There are two ways to exit the Power-down mode: 1. Generate an enabled external interrupt. – The T89C51CC02 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 9) while using KINx input, execution resumes after counting 1024 clock ensuring the oscillator is restarted properly (see Figure 8). 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.
1. 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. 2. Exit from power-down by external interrupt does not affect the SFRs nor the internal RAM content.
Entering Power-down Mode
Exiting Power-down Mode
Note:
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Figure 9. 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 continue for a number of clock cycles before the internal reset algorithm takes control. Reset initializes the T89C51CC02 and vectors the CPU to address 0000h.
1. 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. 2. Exit from power-down by reset redefines all the SFRs, but does not affect the internal RAM content.
Notes:
Table 14. Pin Conditions in Special Operating Modes
Mode Reset Idle (internal code) Idle (external code) PowerDown(inter nal code) PowerDown (external code) Port 0 Floating Port 1 High Port 2 High Port 3 High Port 4 High ALE High PSEN# High
Data
Data
Data
Data
Data
High
High
Floating
Data
Data
Data
Data
High
High
Data
Data
Data
Data
Data
Low
Low
Floating
Data
Data
Data
Data
Low
Low
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Registers
Table 15. PCON Register PCON (S:87h) – Power configuration Register
7 SMOD1 Bit Number 7 6 SMOD0 5 4 POF 3 GF1 2 GF0 1 PD 0 IDL
Bit Mnemonic Description SMOD1 Serial port Mode bit 1 Set to select double baud rate in mode 1, 2 or 3 Serial port Mode bit 0 Clear 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 Clear 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 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.
6
SMOD0
5
-
4
POF
3
GF1
2
GF0
1
PD
0
IDL
Reset Value = 00X1 0000b
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Data Memory
The A/T89C51AC2 provides data memory access in two different spaces: 1. The internal space mapped in three separate segments: • • • the lower 128 Bytes RAM segment. the upper 128 Bytes RAM segment. the expanded 1024 Bytes RAM segment (XRAM).
2. The external space. A fourth internal segment is available but dedicated to Special Function Registers, SFRs, (addresses 80h to FFh) accessible by direct addressing mode. Figure 11 shows the internal and external data memory spaces organization. Figure 10. Internal Memory - RAM
FFh Upper 128 Bytes Internal RAM indirect addressing 80h 7Fh 80h Lower 128 Bytes Internal RAM direct or indirect addressing FFh Special Function Registers direct addressing
00h
Figure 11. Internal and External Data Memory Organization XRAM-XRAM
FFFFh
64 KB External XRAM
FFh or 3FFh 256 up to 1024 Bytes Internal XRAM EXTRAM = 0 00h 0000h
EXTRAM = 1
Internal
External
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Internal Space
Lower 128 Bytes RAM The lower 128 Bytes of RAM (see Figure 11) are accessible from address 00h to 7Fh using direct or indirect addressing modes. The lowest 32 Bytes are grouped into 4 banks of 8 registers (R0 to R7). Two bits RS0 and RS1 in PSW register (see Figure 18) select which bank is in use according to Table 16. This allows more efficient use of code space, since register instructions are shorter than instructions that use direct addressing, and can be used for context switching in interrupt service routines. Table 16. Register Bank Selection
RS1 0 0 1 1 RS0 0 1 0 1 Description Register bank 0 from 00h to 07h Register bank 0 from 08h to 0Fh Register bank 0 from 10h to 17h Register bank 0 from 18h to 1Fh
The next 16 Bytes above the register banks form a block of bit-addressable memory space. The C51 instruction set includes a wide selection of single-bit instructions, and the 128 bits in this area can be directly addressed by these instructions. The bit addresses in this area are 00h to 7Fh. Figure 12. Lower 128 Bytes Internal RAM Organization
7Fh
30h 2Fh 20h 18h 10h 08h 00h 1Fh 17h 0Fh 07h 4 Banks of 8 Registers R0-R7 Bit-Addressable Space (Bit Addresses 0-7Fh)
Upper 128 Bytes RAM
The upper 128 Bytes of RAM are accessible from address 80h to FFh using only indirect addressing mode. The on-chip 1024 Bytes of expanded RAM (XRAM) are accessible from address 0000h to 03FFh using indirect addressing mode through MOVX instructions. In this address range, the bit EXTRAM in AUXR register is used to select the XRAM (default) or the XRAM. As shown in Figure 11 when EXTRAM = 0, the XRAM is selected and when EXTRAM = 1, the XRAM is selected. The size of XRAM can be configured by XRS1-0 bit in AUXR register (default size is 1024 Bytes).
Note: Lower 128 Bytes RAM, Upper 128 Bytes RAM, and expanded RAM are made of volatile memory cells. This means that the RAM content is indeterminate after power-up and must then be initialized properly.
Expanded RAM
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External Space
Memory Interface The external memory interface comprises the external bus (port 0 and port 2) as well as the bus control signals (RD, WR, and ALE). Figure 13 shows the structure of the external address bus. P0 carries address A7:0 while P2 carries address A15:8. Data D7:0 is multiplexed with A7:0 on P0. Table 17 describes the external memory interface signals. Figure 13. External Data Memory Interface Structure
A/T89C51AC2 A15:8 P2 ALE AD7:0 P0 Latch A7:0 A7:0 D7:0 RD WR OE WR A15:8 RAM PERIPHERAL
Table 17. External Data Memory Interface Signals
Signal Name A15:8 Type O Description Address Lines Upper address lines for the external bus. Address/Data Lines Multiplexed lower address lines and data for the external memory. Address Latch Enable ALE signals indicates that valid address information are available on lines AD7:0. Read Read signal output to external data memory. Write Write signal output to external memory. Alternative Function P2.7:0
AD7:0
I/O
P0.7:0
ALE
O
-
RD
O
P3.7
WR
O
P3.6
External Bus Cycles
This section describes the bus cycles the A/T89C51AC2 executes to read (see Figure 14), and write data (see Figure 15) in the external data memory. External memory cycle takes 6 CPU clock periods. This is equivalent to 12 oscillator clock period in standard mode or 6 oscillator clock periods in X2 mode. For further information on X2 mode. Slow peripherals can be accessed by stretching the read and write cycles. This is done using the M0 bit in AUXR register. Setting this bit changes the width of the RD and WR signals from 3 to 15 CPU clock periods. For simplicity, the accompanying figures depict the bus cycle waveforms in idealized form and do not provide precise timing information. For bus cycle timing parameters refer to the Section “AC Characteristics”.
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Figure 14. External Data Read Waveforms
CPU Clock ALE RD 1 P0 P2
P2 DPL or Ri D7:0
DPH or P22
Notes:
1. RD signal may be stretched using M0 bit in AUXR register. 2. When executing MOVX @Ri instruction, P2 outputs SFR content.
Figure 15. External Data Write Waveforms
CPU Clock ALE
WR 1
P0 P2
P2
DPL or Ri
D7:0
DPH or P22
Notes:
1. WR signal may be stretched using M0 bit in AUXR register. 2. When executing MOVX @Ri instruction, P2 outputs SFR content.
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Dual Data Pointer
Description The A/T89C51AC2 implements a second data pointer for speeding up code execution and reducing code size in case of intensive usage of external memory accesses. DPTR 0 and DPTR 1 are seen by the CPU as DPTR and are accessed using the SFR addresses 83h and 84h that are the DPH and DPL addresses. The DPS bit in AUXR1 register (see Figure 20) is used to select whether DPTR is the data pointer 0 or the data pointer 1 (see Figure 16). Figure 16. Dual Data Pointer Implementation
DPL0 DPL1
DPTR0 DPTR1 0
DPL
1
DPS DPH0 DPH1
0
AUXR1.0
DPTR
DPH
1
Application
Software can take advantage of the additional data pointers to both increase speed and reduce code size, for example, block operations (copy, compare…) are well served by using one data pointer as a “source” pointer and the other one as a “destination” pointer. Hereafter is an example of block move implementation using the two pointers and coded in assembler. The latest C compiler takes also advantage of this feature by providing enhanced algorithm libraries. The INC instruction is a short (2 Bytes) and fast (6 machine cycle) way to manipulate the DPS bit in the AUXR1 register. 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.
; ASCII block move using dual data pointers ; Modifies DPTR0, DPTR1, A and PSW ; Ends when encountering NULL character ; Note: DPS exits opposite to the entry state unless an extra INC AUXR1 is added AUXR1EQU0A2h move:movDPTR,#SOURCE ; address of SOURCE incAUXR1 ; switch data pointers movDPTR,#DEST ; address of DEST mv_loop:incAUXR1; switch data pointers movxA,@DPTR; get a byte from SOURCE incDPTR; increment SOURCE address incAUXR1; switch data pointers movx@DPTR,A; write the byte to DEST incDPTR; increment DEST address jnzmv_loop; check for NULL terminator end_move:
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Registers
Table 18. PSW Register PSW (S:D0h) Program Status Word Register
7 CY Bit Number 7 6 AC 5 F0 4 RS1 3 RS0 2 OV 1 F1 0 P
Bit Mnemonic Description CY Carry Flag Carry out from bit 1 of ALU operands. Auxiliary Carry Flag Carry out from bit 1 of addition operands. User Definable Flag 0. Register Bank Select Bits Refer to Table 16 for bits description. Overflow Flag Overflow set by arithmetic operations. User Definable Flag 1 Parity Bit Set when ACC contains an odd number of 1’s. Cleared when ACC contains an even number of 1’s.
6 5 4-3
AC F0 RS1:0
2 1
OV F1
0
P
Reset Value = 0000 0000b Table 19. AUXR Register AUXR (S:8Eh) Auxiliary Register
7 Bit Number 7-6 6 5 M0 4 3 XRS1 2 XRS0 1 EXTRAM 0 A0
Bit Mnemonic Description Reserved The value read from these bits are indeterminate. Do not set this bit. Stretch MOVX control: the RD/ and the WR/ pulse length is increased according to the value of M0. M0 Pulse length in clock period 0 6 1 30 Reserved The value read from this bit is indeterminate. Do not set this bit. XRAM size: Accessible size of the XRAM XRS 1:0 XRAM size 0 0 256 Bytes 0 1 512 Bytes 1 0 768 Bytes 1 1 1024 Bytes (default)
5
M0
4
-
3-2
XRS1-0
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Bit Number Bit Mnemonic Description Internal/External RAM (00h - FFh) access using MOVX @ Ri/@ DPTR 0 - Internal XRAM access using MOVX @ Ri/@ DPTR. 1 - External data memory access. Disable/Enable ALE) 0 - ALE is emitted at a constant rate of 1/6 the oscillator frequency (or 1/3 if X2 mode is used) 1 - ALE is active only during a MOVX or MOVC instruction.
1
EXTRAM
0
A0
Reset Value = X00X 1100b Not bit addressable Table 20. AUXR1 Register AUXR1 (S:A2h) Auxiliary Control Register 1
7 Bit Number 7-6 6 Bit Mnemonic 5 ENBOOT 4 3 GF3 2 0 1 0 DPS
Description Reserved The value read from these bits is indeterminate. Do not set these bits.
5
Enable Boot Flash ENBOOT(1) Set this bit for map the boot Flash between F800h -FFFFh Clear this bit for disable boot Flash. GF3 Reserved The value read from this bit is indeterminate. Do not set this bit. General-purpose Flag 3 Always Zero This bit is stuck to logic 0 to allow INC AUXR1 instruction without affecting GF3 flag. Reserved for Data Pointer Extension. Data Pointer Select Bit Set to select second dual data pointer: DPTR1. Clear to select first dual data pointer: DPTR0.
4 3
2
0
1
-
0
DPS
Reset Value = XXXX 00X0b
Note: 1. ENBOOT is initialized with the invert BLJB at reset. See In-System Programming section.
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EEPROM Data Memory
The 2 KB on-chip EEPROM memory block is located at addresses 0000h to 07FFh of the XRAM/XRAM memory space and is selected by setting control bits in the EECON register. A read in the EEPROM memory is done with a MOVX instruction. A physical write in the EEPROM memory is done in two steps: write data in the column latches and transfer of all data latches into an EEPROM memory row (programming). The number of data written on the page may vary from 1 up to 128 Bytes (the page size). When programming, only the data written in the column latch is programmed and a ninth bit is used to obtain this feature. This provides the capability to program the whole memory by Bytes, by page or by a number of Bytes in a page. Indeed, each ninth bit is set when the writing the corresponding byte in a row and all these ninth bits are reset after the writing of the complete EEPROM row.
Write Data in the Column Latches
Data is written by byte to the column latches as for an external RAM memory. Out of the 11 address bits of the data pointer, the 4 MSBs are used for page selection (row) and 7 are used for byte selection. Between two EEPROM programming sessions, all the addresses in the column latches must stay on the same page, meaning that the 4 MSB must no be changed. The following procedure is used to write to the column latches: • • • • • • • Save and disable interrupt. Set bit EEE of EECON register Load DPTR with the address to write Store A register with the data to be written Execute a MOVX @DPTR, A If needed loop the three last instructions until the end of a 128 Bytes page Restore interrupt.
The last page address used when loading the column latch is the one used to select the page programming address.
Note:
Programming
The EEPROM programming consists of the following actions: • writing one or more Bytes of one page in the column latches. Normally, all Bytes must belong to the same page; if not, the last page address will be latched and the others discarded. launching programming by writing the control sequence (50h followed by A0h) to the EECON register. 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. The end of programming is indicated by a hardware clear of the EEBUSY flag.
The sequence 5xh and Axh must be executed without instructions between then otherwise the programming is aborted.
• • •
Note:
Read Data
The following procedure is used to read the data stored in the EEPROM memory: • • • • • Save and disable interrupt Set bit EEE of EECON register Load DPTR with the address to read Execute a MOVX A, @DPTR Restore interrupt
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Examples
;*F************************************************************************* ;* NAME: api_rd_eeprom_byte ;* DPTR contain address to read. ;* Acc contain the reading value ;* NOTE: before execute this function, be sure the EEPROM is not BUSY ;*************************************************************************** api_rd_eeprom_byte: ; Save and clear EA MOV MOV ret EECON, #02h; map EEPROM in XRAM space EECON, #00h; unmap EEPROM
MOVX A, @DPTR ; Restore EA
;*F************************************************************************* ;* NAME: api_ld_eeprom_cl ;* DPTR contain address to load ;* Acc contain value to load ;* NOTE: in this example we load only 1 byte, but it is possible upto ;* 128 Bytes. ;* before execute this function, be sure the EEPROM is not BUSY ;*************************************************************************** api_ld_eeprom_cl: ; Save and clear EA MOV EECON, #02h ; map EEPROM in XRAM space MOVX @DPTR, A MOVEECON, #00h; unmap EEPROM ; Restore EA ret ;*F************************************************************************* ;* NAME: api_wr_eeprom ;* NOTE: before execute this function, be sure the EEPROM is not BUSY ;*************************************************************************** api_wr_eeprom: ; Save and clear EA MOV MOV ret EECON, #050h EECON, #0A0h
; Restore EA
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Registers
Table 21. EECON Register EECON (S:0D2h) EEPROM Control Register
7 EEPL3 6 EEPL2 Bit Mnemonic EEPL3-0 5 EEPL1 4 EEPL0 3 2 1 EEE 0 EEBUSY
Bit Number 7-4
Description Programming Launch command bits Write 5Xh followed by AXh to EEPL to launch the programming. 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 EEPROM Space bit Set to map the EEPROM space during MOVX instructions (Write in the column latches) 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.
3
-
2
-
1
EEE
0
EEBUSY
Reset Value = XXXX XX00b Not bit addressable
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Program/Code Memory
The A/T89C51AC2 implement 32 KB of on-chip program/code memory. Figure 17 shows the partitioning of internal and external program/code memory spaces depending on the product. The Flash memory increases EPROM and ROM functionality by in-circuit electrical erasure and programming. Thanks to the internal charge pump, the high voltage needed for programming or erasing Flash cells is generated on-chip using the standard VDD voltage. Thus, the Flash Memory can be programmed using only one voltage and allows InSystem-Programming commonly known as ISP. Hardware programming mode is also available using specific programming tool. Figure 17. Program/Code Memory Organization
FFFFh
32 KB external memory
8000h 7FFFh 32 KB internal Flash EA = 1 0000h 0000h 7FFFh 32 KB external memory EA = 0
Notes:
1. If the program executes exclusively from on-chip code memory (not from external memory), beware of executing code from the upper byte of on-chip memory (7FFFh) and thereby disrupt I/O Ports 0 and 2 due to external prefetch. Fetching code constant from this location does not affect Ports 0 and 2. 2. Default factory programmed parts come with maximum hardware protection. Execution from external memory is not possible unless the Hardware Security Byte is reprogrammed. See Table 26.
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External Code Memory Access
Memory Interface The external memory interface comprises the external bus (port 0 and port 2) as well as the bus control signals (PSEN#, and ALE). Figure 18 shows the structure of the external address bus. P0 carries address A7:0 while P2 carries address A15:8. Data D7:0 is multiplexed with A7:0 on P0. Table 18 describes the external memory interface signals. Figure 18. External Code Memory Interface Structure
A/T89C51AC2 A15:8 P2 ALE AD7:0 P0 Latch A7:0 A7:0 D7:0 PSEN# OE A15:8 Flash EPROM
Table 22. External Code Memory Interface Signals
Signal Name A15:8 Type O Description Address Lines Upper address lines for the external bus. Address/Data Lines Multiplexed lower address lines and data for the external memory. Address Latch Enable ALE signals indicates that valid address information are available on lines AD7:0. Program Store Enable Output This signal is active low during external code fetch or external code read (MOVC instruction). Alternate Function P2.7:0
AD7:0
I/O
P0.7:0
ALE
O
-
PSEN#
O
-
External Bus Cycles
This section describes the bus cycles the A/T89C51AC2 executes to fetch code (see Figure 19) in the external program/code memory. External memory cycle takes 6 CPU clock periods. This is equivalent to 12 oscillator clock period in standard mode or 6 oscillator clock periods in X2 mode. For further information on X2 mode see section “Clock “. For simplicity, the accompanying figure depicts the bus cycle waveforms in idealized form and do not provide precise timing information. For bus cycling parameters refer to the ‘AC-DC parameters’ section.
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Figure 19. External Code Fetch Waveforms
CPU Clock ALE PSEN# P0 D7:0 P2 PCH
PCL D7:0 PCL D7:0
PCH
PCH
Flash Memory Architecture
A/T89C51AC2 features two on-chip Flash memories: • • Flash memory FM0: containing 32 KB of program memory (user space) organized into 128 byte pages, Flash memory FM1: 2 KB for boot loader and Application Programming Interfaces (API).
The FM0 can be program by both parallel programming and Serial In-System-Programming (ISP) whereas FM1 supports only parallel programming by programmers. The ISP mode is detailed in the "In-System-Programming" section. All Read/Write access operations on Flash Memory by user application are managed by a set of API described in the "In-System-Programming" section. Figure 20. Flash Memory Architecture
2 KB Flash memory boot space FM1
FFFFh
Hardware Security (1 byte) E xtra Row (128 Bytes) Column Latches (128 Bytes)
F800h
7FFFh
32 KB Flash memory user space FM0
FM1 mapped between F800h and FFFFh when bit ENBOOT is set in AUXR1 register
0000h
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FM0 Memory Architecture
The Flash memory is made up of 4 blocks (see Figure 20): • • • • The memory array (user space) 32 KB The Extra Row The Hardware security bits The column latch registers
User Space
This space is composed of a 32 KB Flash memory organized in 256 pages of 128 Bytes. It contains the user’s application code. This row is a part of FM0 and has a size of 128 Bytes. The extra row may contain information for boot loader usage. The Hardware security Byte space is a part of FM0 and has a size of 1 byte. The 4 MSB can be read/written by software, the 4 LSB can only be read by software and written by hardware in parallel mode. The column latches, also part of FM0, have a size of full page (128 Bytes). The column latches are the entrance buffers of the three previous memory locations (user array, XROW and Hardware security byte). The FM0 memory can be program only from FM1. Programming FM0 from FM0 or from external memory is impossible. The FM1 memory can be program only by parallel programming. The Table 23 show all software Flash access allowed. Table 23. Cross Flash Memory Access
Action Read Code executing from Load column latch FM0 (user Flash) Write Read Load column latch FM1 (boot Flash) Write Read External memory EA = 0 Load column latch Write FM0 (user Flash) ok ok ok ok ok FM1 (boot Flash) ok -
Extra Row (XRow)
Hardware Security Byte
Column Latches
Cross Flash Memory Access Description
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Overview of FM0 Operations
The CPU interfaces to the Flash memory through the FCON register and AUXR1 register. These registers are used to: • • • Map the memory spaces in the adressable space Launch the programming of the memory spaces Get the status of the Flash memory (busy/not busy)
Mapping of the Memory Space By default, the user space is accessed by MOVC instruction for read only. The column latches space is made accessible by setting the FPS bit in FCON register. Writing is possible from 0000h to 7FFFh, address bits 6 to 0 are used to select an address within a page while bits 14 to 7 are used to select the programming address of the page. Setting FPS bit takes precedence on the EXTRAM bit in AUXR register. The other memory spaces (user, extra row, hardware security) are made accessible in the code segment by programming bits FMOD0 and FMOD1 in FCON register in accordance with Table 24. A MOVC instruction is then used for reading these spaces. Table 24. FM0 Blocks Select Bits
FMOD1 0 0 1 1 FMOD0 0 1 0 1 FM0 Adressable space User (0000h-7FFFh) Extra Row(FF80h-FFFFh) Hardware Security Byte (0000h) Reserved
Launching Programming
FPL3:0 bits in FCON register are used to secure the launch of programming. A specific sequence must be written in these bits to unlock the write protection and to launch the programming. This sequence is 5xh followed by Axh. Table 25 summarizes the memory spaces to program according to FMOD1:0 bits.
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Table 25. Programming Spaces
Write to FCON FPL3:0 5 A 5 A 5 A 5 Reserved A FPS X X X X X X X X FMOD1 0 0 0 0 1 1 1 1 FMOD0 0 0 1 1 0 0 1 1 Operation No action Write the column latches in user space No action Write the column latches in extra row space No action Write the fuse bits space No action No action
User
Extra Row Hardware Security Byte
Notes:
1. The sequence 5xh and Axh must be executing without instructions between them otherwise the programming is aborted. 2. Interrupts that may occur during programming time must be disabled to avoid any spurious exit of the programming mode.
Status of the Flash Memory
The bit FBUSY in FCON register is used to indicate the status of programming. FBUSY is set when programming is in progress.
Selecting FM1 Loading the Column Latches
The bit ENBOOT in AUXR1 register is used to map FM1 from F800h to FFFFh. Any number of data from 1 Byte to 128 Bytes can be loaded in the column latches. This provides the capability to program the whole memory by byte, by page or by any number of Bytes in a page. When programming is launched, an automatic erase of the locations loaded in the column latches is first performed, then programming is effectively done. Thus no page or block erase is needed and only the loaded data are programmed in the corresponding page. The following procedure is used to load the column latches and is summarized in Figure 21: • • • • • • Save then disable interrupt and map the column latch space by setting FPS bit. Load the DPTR with the address to load. Load Accumulator register with the data to load. Execute the MOVX @DPTR, A instruction. If needed loop the three last instructions until the page is completely loaded. Unmap the column latch and Restore Interrupt
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Figure 21. Column Latches Loading Procedure
Column Latches Loading
Save and Disable IT EA = 0
Column Latches Mapping FCON = 08h (FPS=1)
Data Load DPTR = Address ACC = Data Exec: MOVX @DPTR, A
Last Byte to load?
Data memory Mapping FCON = 00h (FPS = 0)
Restore IT
Note:
The last page address used when loading the column latch is the one used to select the page programming address.
Programming the Flash Spaces User The following procedure is used to program the User space and is summarized in Figure 22: • • • Load up to one page of data in the column latches from address 0000h to 7FFFh. Save then disable the interrupts. Launch the programming by writing the data sequence 50h followed by A0h in FCON register (only from FM1). The end of the programming indicated by the FBUSY flag cleared. Restore the interrupts.
• Extra Row
The following procedure is used to program the Extra Row space and is summarized in Figure 22: • • • Load data in the column latches from address FF80h to FFFFh. Save then disable the interrupts. Launch the programming by writing the data sequence 52h followed by A2h in FCON register. This step of the procedure must be executed from FM1. The end of the programming indicated by the FBUSY flag cleared. The end of the programming indicated by the FBUSY flag cleared. Restore the interrupts.
•
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Figure 22. Flash and Extra Row Programming Procedure
Flash Spaces Programming
Column Latches Loading see Figure 21
Save and Disable IT EA = 0
Launch Programming FCON = 5xh FCON = Axh
FBusy Cleared?
Clear Mode FCON = 00h
End Programming Restore IT
Hardware Security Byte
The following procedure is used to program the Hardware Security B yte space and is summarized in Figure 23: • • • • • • Set FPS and map Hardware byte (FCON = 0x0C) Save and disable the interrupts. Load DPTR at address 0000h. Load Accumulator register with the data to load. Execute the MOVX @DPTR, A instruction. Launch the programming by writing the data sequence 54h followed by A4h in FCON register. This step of the procedure must be executed from FM1. The end of the programming indicated by the FBUSY flag cleared. The end of the programming indicated by the FBusy flag cleared. Restore the interrupts.
•
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Figure 23. Hardware Programming Procedure
Flash Spaces Programming
Save and Disable IT EA = 0 Save and Disable IT EA = 0 Launch Programming FCON = 54h FCON = A4h
FCON = 0Ch
Data Load DPTR = 00h ACC = Data Exec: MOVX @DPTR, A
FBusy Cleared?
End Loading Restore IT
Clear Mode FCON = 00h
End Programming RestoreIT
Reading the Flash Spaces User The following procedure is used to read the User space: • Read one byte in Accumulator by executing MOVC A,@A+DPTR where A+DPTR is the address of the code byte to read.
FCON is supposed to be reset when not needed.
Note:
Extra Row
The following procedure is used to read the Extra Row space and is summarized in Figure 24: • • • Map the Extra Row space by writing 02h in FCON register. Read one byte in Accumulator by executing MOVC A,@A+DPTR with A = 0 and DPTR = FF80h to FFFFh. Clear FCON to unmap the Extra Row.
Hardware Security Byte
The following procedure is used to read the Hardware Security space and is summarized in Figure 24: • • • Map the Hardware Security space by writing 04h in FCON register. Read the byte in Accumulator by executing MOVC A,@A+DPTR with A = 0 and DPTR = 0000h. Clear FCON to unmap the Hardware Security Byte.
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Figure 24. Reading Procedure
Flash Spaces Reading
Flash Spaces Mapping FCON = 0000aa0b(1)
Data Read DPTR = Address ACC = 0 Exec: MOVC A, @A+DPTR
Clear Mode FCON = 00h
Note:
1. aa = 10 for the Hardware Security Byte.
Flash Protection from Parallel Programming
The three lock bits in Hardware Security Byte (see "In-System-Programming" section) are programmed according to Table 26 provide different level of protection for the onchip code and data located in FM0 and FM1. The only way to write these bits are the parallel mode. They are set by default to level 4 Table 26. Program Lock bit
Program Lock Bits Security Level 1 LB0 LB1 LB2
Protection Description No program lock features enabled. MOVC instruction executed from external program memory returns non coded data. MOVC instructions executed from external program memory are barred to return code bytes from internal memory, EA is sampled and latched on reset, and further parallel programming of the Flash is disabled. Same as 2, also verify through parallel programming interface is disabled. Same as 3, also external execution is disabled if code roll over beyond 7FFFh
U
U
U
2
P
U
U
3
U
P
U
4
U
U
P
Program Lock bits U: unprogrammed P: programmed WARNING: Security level 2 and 3 should only be programmed after Flash and Core verification. Preventing Flash Corruption See the “Power Management” section.
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Registers
FCON RegisterFCON (S:D1h) Flash Control Register
7 FPL3 Bit Number 6 FPL2 5 FPL1 4 FPL0 3 FPS 2 FMOD1 1 FMOD0 0 FBUSY
Bit Mnemonic Description Programming Launch Command Bits Write 5Xh followed by AXh to launch the programming according to FMOD1:0 (see Table 25) Flash Map Program Space Set to map the column latch space in the data memory space. Clear to re-map the data memory space. Flash Mode See Table 24 or Table 25. Flash Busy Set by hardware when programming is in progress. Clear by hardware when programming is done. Can not be changed by software.
7-4
FPL3:0
3
FPS
2-1
FMOD1:0
0
FBUSY
Reset Value = 0000 0000b
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Operation Cross Memory Access
Space addressable in read and write are: • • • • • • • • • RAM ERAM (Expanded RAM access by movx) XRAM (eXternal RAM) EEPROM DATA FM0 (user flash) Hardware byte XROW Boot Flash Flash Column latch
The table below provide the different kind of memory which can be accessed from different code location. Table 27. Cross Memory Access
XRAM Action Read boot FLASH Write Read FM0 Write External memory EA = 0 or Code Roll Over Write OK (1) Read OK (idle) OK (1) OK OK OK OK(1) OK OK(1) OK OK(1) OK OK(1) RAM ERAM Boot FLASH OK FM0 OK E² Data OK Hardware Byte OK XROW -
Note:
1. RWW: Read While Write
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Sharing Instructions
Table 28. Instructions shared
XRAM Action Read Write RAM MOV MOV ERAM MOVX MOVX EEPROM DATA MOVX MOVX Boot FLASH MOVC FM0 MOVC by cl Hardware Byte MOVC by cl XROW MOVC by cl
Note:
by cl: using Column Latch
Table 29. Read MOVX A, @DPTR
EEE bit in EECON Register 0 0 1 1 FPS in FCON Register 0 1 0 1 ENBOOT X X X X EA X X X X OK XRAM ERAM OK OK OK EEPROM DATA Flash Column Latch
Table 30. Write MOVX @DPTR,A
EEE bit in EECON Register 0 0 1 1 FPS bit in FCON Register 0 1 0 1 ENBOOT X X 0 X X 0 OK X 1 OK OK OK EA X 1 XRAM ERAM OK OK EEPROM Data Flash Column Latch
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Table 31. Read MOVC A, @DPTR
FCON Register Code Execution FMOD1 FMOD0 FPS ENBOOT 0 0 0 X 1 F800h to FFFFh 0 From FM0 1 0 X X 0 1 1 X 1 F800h to FFFFh 0000h to 7FFF 1 0 0 0 1 0 From FM1 (ENBOOT =1 0 1 X 0 1 1 0 X 0 1 1 External code : EA=0 or Code Roll Over X 0 X X X OK 1 X 0 000h to 7FFFh NA OK X NA 1 X 0000h to 007h See
(2)
Hardware DPTR 0000h to 7FFFh 0000h to 7FFFh FM1 FM0 OK OK Do not use this configuration OK OK OK OK Do not use this configuration OK OK NA OK NA OK NA OK XROW Byte
External Code
1
X
X
0000 to 007Fh See (1) X 000h to 7FFFh 0000h to 7FFFh
F800h to FFFFh 0 1 X X
1. For DPTR higher than 007Fh only lowest 7 bits are decoded, thus the behavior is the same as for addresses from 0000h to 007Fh 2. For DPTR higher than 007Fh only lowest 7 bits are decoded, thus the behavior is the same as for addresses from 0000h to 007Fh
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In-System Programming (ISP)
With the implementation of the User Space (FM0) and the Boot Space (FM1) in Flash technology the A/T89C51AC2 allows the system engineer the development of applications with a very high level of flexibility. This flexibility is based on the possibility to alter the customer program at any stages of a product’s life: • Before mounting the chip on the PCB, FM0 Flash can be programmed with the application code. FM1 is always preprogrammed by Atmel with a bootloader (UART bootloader). (1) Once the chip is mounted on the PCB, it can be programmed by serial mode via the UART.
1. The user can also program his own bootloader in FM1.
•
Note:
This In-System-Programming (ISP) allows code modification over the total lifetime of the product. Besides the default Boot loader Atmel provide to the customer also all the needed Application-Programming-Interfaces (API) which are needed for the ISP. The API are located also in the Boot memory. This allow the customer to have a full use of the 32 KB user memory.
Flash Programming and Erasure
There are three methods of programming the Flash memory: • The Atmel bootloader located in FM1 is activated by the application. Low level API routines (located in FM1) will be used to program FM0. The interface used for serial downloading to FM0 is the UART. API can be called also by the user’s bootloader located in FM0 at [SBV]00h. A further method exists in activating the Atmel boot loader by hardware activation. See Section “Hardware Security Byte”. The FM0 can be programmed also by the parallel mode using a programmer.
• •
Figure 25. Flash Memory Mapping FFFFh
2 KB IAP bootloader FM1
F800h
7FFFh
Custom Boot Loader [SBV]00h 32 KB Flash memory FM0
FM1 mapped between F800h and FFFFh when API called
0000h
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Boot Process
Software Boot Process Example Many algorithms can be used for the software boot process. Below are descriptions of the different flags and Bytes. Boot Loader Jump Bit (BLJB): - This bit indicates if on RESET the user wants to jump to this application at address @0000h on FM0 or execute the boot loader at address @F800h on FM1. - BLJB = 0 (i.e. bootloader FM1 executed after a reset) is the default Atmel factory programming. - To read or modify this bit, the APIs are used. Boot Vector Address (SBV): - This byte contains the MSB of the user boot loader address in FM0. - The default value of SBV is FCh (no user boot loader in FM0). - To read or modify this byte, the APIs are used. Extra Byte (EB) and Boot Status Byte (BSB): - These Bytes are reserved for customer use. - To read or modify these Bytes, the APIs are used. Hardware Boot Process At the falling edge of RESET, the bit ENBOOT in AUXR1 register is initialized with the value of Boot Loader Jump Bit (BLJB). Further at the falling edge of RESET if the following conditions (called Hardware condition) are detected. The FCON register is initialized with the value 00h and the PC is initialized with F800h (FM1 lower byte = Bootloader entry point). Harware Conditions: • • • PSEN low (1) EA high, ALE high (or not connected).
The Hardware condition forces the bootloader to be executed, whatever BLJB value is. Then BLBJ will be checked. If no hardware condition is detected, the FCON register is initialized with the value F0h. Then BLJB value will be checked. Conditions are: • • If bit BLJB = 1: User application in FM0 will be started at @0000h (standard reset). If bit BLJB = 0: Boot loader will be started at @F800h in FM1.
1. As PSEN is an output port in normal operating mode (running user applications or bootloader applications) after reset it is recommended to release PSEN after the falling edge of Reset is signaled. The hardware conditions are sampled at reset signal Falling Edge, thus they can be released at any time when reset input is low. 2. To ensure correct microcontroller startup, the PSEN pin should not be tied to ground during power-on.
Note:
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Figure 26. Hardware Boot Process Algorithm RESET bit ENBOOT in AUXR1 register is initialized with BLJB inverted.
(Example, if BLJB=0, ENBOOT is set (=1) during reset, thus the bootloader is executed after the reset)
Hardware
Hardware condition? ENBOOT = 0 PC = 0000h No No
Yes
ENBOOT = 1 PC = F800h FCON = 00h
FCON = F0h
BLJB = = 0 ? Yes ENBOOT = 1 PC = F800h
Software
Application in FM0
Boot Loader in FM1
Application Programming Interface
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 by functions. All of these APIs are described in detail in the following documents on the Atmel web site. • Datasheet Bootloader UART A/T89C51AC2
XROW Bytes
Table 32. XROW Mapping
Description 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 58h D7h F7h FFh Address 30h 31h 60h 61h
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Hardware Security Byte
Table 33. Hardware Security Byte
7 X2B Bit Number 6 BLJB 5 4 3 2 LB2 1 LB1 0 LB0
Bit Mnemonic Description X2 Bit Set this bit to start in standard mode. Clear this bit to start in X2 mode. Boot Loader JumpBit - 1: To start the user’s application on next RESET (@0000h) located in FM0, - 0: To start the boot loader(@F800h) located in FM1. Reserved The value read from these bits are indeterminate. Lock Bits
7
X2B
6
BLJB
5-3 2-0
LB2:0
After erasing the chip in parallel mode, the default value is : FFh The erasing in ISP mode (from bootloader) does not modify this byte.
Notes: 1. Only the 4 MSB bits can be accessed by software. 2. The 4 LSB bits can only be accessed by parallel mode.
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Serial I/O Port
The A/T89C51AC2 I/O serial port is compatible with the I/O serial 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
Figure 27. Serial I/O Port Block Diagram
IB Bus
Write SBUF SBUF Receiver
Read SBUF
TXD
SBUF Transmitter Mode 0 Transmit
Load SBUF
RXD
Receive Shift register Serial Port Interrupt Request
RI
TI
SCON reg
Framing Error Detection Framing bit error detection is provided for the three asynchronous modes. To enable the
framing bit error detection feature, set SMOD0 bit in PCON register. Figure 28. Framing Error Block Diagram
SM0/FE SM1 SM2 REN TB8 RB8 TI RI
Set FE bit if stop bit is 0 (framing error) SM0 to UART mode control SMOD1SMOD0 POF GF1 GF0 PD IDL
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 bit is set. The software may examine the FE bit after each reception to check for data errors. Once set, only software or a reset clears the FE bit. Subsequently received frames with valid stop bits cannot clear the FE bit. When the FE feature is enabled, RI rises on the stop bit instead of the last data bit (See Figure 29. and Figure 30.).
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Figure 29. UART Timing in Mode 1
RXD Start bit RI SMOD0=X FE SMOD0=1 D0 D1 D2 D3 D4 D5 D6 D7 Stop bit
Data byte
Figure 30. UART Timing 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
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 the 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 will the receiver set the RI bit in the SCON register to generate an interrupt. This ensures that the CPU is not interrupted by command frames addressed to other devices. If necessary, you can 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).
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Given Address
Each device has an individual address that is specified in the 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
Here 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
Slave C:SADDR1111 0011b 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 0; for slaves B and C, bit 1 is a don’t care bit. To communicate with slaves A and B, but not slave C, 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).
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.:
SADDR 0101 0110b SADEN 1111 1100b 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 Given1111 1X11b, Slave B:SADDR1111 0011b SADEN1111 1001b Given1111 1X11B, Slave C:SADDR=1111 0010b SADEN1111 1101b Given1111 1111b
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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.
Registers
Table 34. SCON Register SCON (S:98h) Serial Control Register
7 FE/SM0 Bit Number 6 SM1 5 SM2 4 REN 3 TB8 2 RB8 1 TI 0 RI
Bit Mnemonic Description Framing Error bit (SMOD0=1) Clear to reset the error state, not cleared by a valid stop bit. Set by hardware when an invalid stop bit is detected. Serial port Mode bit 0 (SMOD0=0) Refer to SM1 for serial port mode selection. Serial port Mode bit 1 SM0 SM1 Mode 0 0 Shift Register 0 1 8-bit UART 1 0 9-bit UART 1 1 9-bit UART
FE 7 SM0
6
SM1
Baud Rate FXTAL/12 (or FXTAL /6 in mode X2) Variable FXTAL/64 or FXTAL/32 Variable
5
SM2
Serial port Mode 2 bit/Multiprocessor Communication Enable bit Clear to disable multiprocessor communication feature. Set to enable multiprocessor communication feature in mode 2 and 3. 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 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. 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 29. and Figure 30. in the other modes.
4
REN
3
TB8
2
RB8
1
TI
0
RI
Reset Value = 0000 0000b Bit addressable
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A/T89C51AC2
Table 35. SADEN Register SADEN (S:B9h) Slave Address Mask Register
7 – Bit Number 7-0 6 – 5 – 4 – 3 – 2 – 1 – 0 –
Bit Mnemonic Description Mask Data for Slave Individual Address
Reset Value = 0000 0000b Not bit addressable Table 36. SADDR Register SADDR (S:A9h) Slave Address Register
7 – Bit Number 7-0 6 – 5 – 4 – 3 – 2 – 1 – 0 –
Bit Mnemonic Description Slave Individual Address
Reset Value = 0000 0000b Not bit addressable Table 37. SBUF Register SBUF (S:99h) Serial Data Buffer
7 – Bit Number 7-0 6 – 5 – 4 – 3 – 2 – 1 – 0 –
Bit Mnemonic Description Data sent/received by Serial I/O Port
Reset Value = 0000 0000b Not bit addressable
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Table 38. PCON Register PCON (S:87h) Power Control Register
7 SMOD1 Bit Number 7 6 SMOD0 5 – 4 POF 3 GF1 2 GF0 1 PD 0 IDL
Bit Mnemonic Description SMOD1 Serial port Mode bit 1 Set to select double baud rate in mode 1, 2 or 3. Serial port Mode bit 0 Clear 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 Clear 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 Clear by hardware when interrupt or reset occurs. Set to enter idle mode.
6
SMOD0
5
-
4
POF
3
GF1
2
GF0
1
PD
0
IDL
Reset Value = 00X1 0000b Not bit addressable
56
A/T89C51AC2
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A/T89C51AC2
Timers/Counters
The A/T89C51AC2 implements two general-purpose, 16-bit Timers/Counters. Such are identified as Timer 0 and Timer 1, and can be independently configured to operate in a variety of modes as a Timer or an event Counter. When operating as a Timer, the Timer/Counter runs for a programmed length of time, then issues an interrupt request. When operating as a Counter, the Timer/Counter counts negative transitions on an external pin. After a preset number of counts, the Counter issues an interrupt request. The various operating modes of each Timer/Counter are described in the following sections. A basic operation is Timer registers THx and TLx (x = 0, 1) connected in cascade to form a 16-bit Timer. Setting the run control bit (TRx) in TCON register (see Figure 39) turns the Timer on by allowing the selected input to increment TLx. When TLx overflows it increments THx; when THx overflows it sets the Timer overflow flag (TFx) in TCON register. Setting the TRx does not clear the THx and TLx Timer registers. Timer registers can be accessed to obtain the current count or to enter preset values. They can be read at any time but TRx bit must be cleared to preset their values, otherwise the behavior of the Timer/Counter is unpredictable. The C/Tx# control bit selects Timer operation or Counter operation by selecting the divided-down peripheral clock or external pin Tx as the source for the counted signal. TRx bit must be cleared when changing the mode of operation, otherwise the behavior of the Timer/Counter is unpredictable. For Timer operation (C/Tx# = 0), the Timer register counts the divided-down peripheral clock. The Timer register is incremented once every peripheral cycle (6 peripheral clock periods). The Timer clock rate is FPER/6, i.e. FOSC/12 in standard mode or FOSC/6 in X2 mode. For Counter operation (C/Tx# = 1), the Timer register counts the negative transitions on the Tx external input pin. The external input is sampled every peripheral cycles. When the sample is high in one cycle and low in the next one, the Counter is incremented. Since it takes 2 cycles (12 peripheral clock periods) to recognize a negative transition, the maximum count rate is FPER/12, i.e. F OSC/24 in standard mode or FOSC/12 in X2 mode. There are no restrictions on the duty cycle of the external input signal, but to ensure that a given level is sampled at least once before it changes, it should be held for at least one full peripheral cycle.
Timer/Counter Operations
Timer 0
Timer 0 functions as either a Timer or event Counter in four modes of operation. Figure 31 to Figure 34 show the logical configuration of each mode. Timer 0 is controlled by the four lower bits of TMOD register (see Figure 40) and bits 0, 1, 4 and 5 of TCON register (see Figure 39). TMOD register selects the method of Timer gating (GATE0), Timer or Counter operation (T/C0#) and mode of operation (M10 and M00). TCON register provides Timer 0 control functions: overflow flag (TF0), run control bit (TR0), interrupt flag (IE0) and interrupt type control bit (IT0). For normal Timer operation (GATE0 = 0), setting TR0 allows TL0 to be incremented by the selected input. Setting GATE0 and TR0 allows external pin INT0# to control Timer operation. Timer 0 overflow (count rolls over from all 1s to all 0s) sets TF0 flag generating an interrupt request. It is important to stop Timer/Counter before changing mode.
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Mode 0 (13-bit Timer)
Mode 0 configures Timer 0 as an 13-bit Timer which is set up as an 8-bit Timer (TH0 register) with a modulo 32 prescaler implemented with the lower five bits of TL0 register (see Figure 31). The upper three bits of TL0 register are indeterminate and should be ignored. Prescaler overflow increments TH0 register.
Figure 31. Timer/Counter x (x = 0 or 1) in Mode 0
See the “Clock” section
FTx CLOCK ÷6 0 1
THx (8 bits)
TLx (5 bits)
Overflow
TFx
TCON reg
Tx C/Tx#
TMOD reg
Timer x Interrupt Request
INTx# GATEx
TMOD reg
TRx
TCON reg
Mode 1 (16-bit Timer)
Mode 1 configures Timer 0 as a 16-bit Timer with TH0 and TL0 registers connected in cascade (see Figure 32). The selected input increments TL0 register.
Figure 32. Timer/Counter x (x = 0 or 1) in Mode 1
See the “Clock” section
FTx CLOCK ÷6 0 1
THx (8 bits)
TLx (8 bits)
Overflow
TFx
TCON reg
Tx C/Tx#
TMOD reg
Timer x Interrupt Request
INTx# GATEx
TMOD reg
TRx
TCON reg
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Mode 2 (8-bit Timer with AutoReload) Mode 2 configures Timer 0 as an 8-bit Timer (TL0 register) that automatically reloads from TH0 register (see Figure 33). TL0 overflow sets TF0 flag in TCON register and reloads TL0 with the contents of TH0, which is preset by software. When the interrupt request is serviced, hardware clears TF0. The reload leaves TH0 unchanged. The next reload value may be changed at any time by writing it to TH0 register.
Figure 33. Timer/Counter x (x = 0 or 1) in Mode 2
See the “Clock” section
FTx CLOCK ÷6 0 1
TLx (8 bits)
Overflow
TFx
TCON reg
Tx C/Tx#
TMOD reg
Timer x Interrupt Request
INTx# GATEx
TMOD reg
TRx
TCON reg
THx (8 bits)
Mode 3 (Two 8-bit Timers)
Mode 3 configures Timer 0 such that registers TL0 and TH0 operate as separate 8-bit Timers (see Figure 34). This mode is provided for applications requiring an additional 8bit Timer or Counter. TL0 uses the Timer 0 control bits C/T0# and GATE0 in TMOD register, and TR0 and TF0 in TCON register in the normal manner. TH0 is locked into a Timer function (counting FPER /6) and takes over use of the Timer 1 interrupt (TF1) and run control (TR1) bits. Thus, operation of Timer 1 is restricted when Timer 0 is in mode 3.
Figure 34. Timer/Counter 0 in Mode 3: Two 8-bit Counters
FTx CLOCK ÷6 0 1
TL0 (8 bits)
Overflow
TF0
TCON.5
T0 C/T0#
TMOD.2
Timer 0 Interrupt Request
INT0# GATE0
TMOD.3
TR0
TCON.4
FTx CLOCK
÷6
TH0 (8 bits) TR1
TCON.6
Overflow
TF1
TCON.7
Timer 1 Interrupt Request
See the “Clock” section
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Timer 1
Timer 1 is identical to Timer 0 excepted for Mode 3 which is a hold-count mode. The following comments help to understand the differences: • Timer 1 functions as either a Timer or event Counter in three modes of operation. Figure 31 to Figure 33 show the logical configuration for modes 0, 1, and 2. Timer 1’s mode 3 is a hold-count mode. Timer 1 is controlled by the four high-order bits of TMOD register (see Figure 40) and bits 2, 3, 6 and 7 of TCON register (see Figure 39). TMOD register selects the method of Timer gating (GATE1), Timer or Counter operation (C/T1#) and mode of operation (M11 and M01). TCON register provides Timer 1 control functions: overflow flag (TF1), run control bit (TR1), interrupt flag (IE1) and interrupt type control bit (IT1). Timer 1 can serve as the Baud Rate Generator for the Serial Port. Mode 2 is best suited for this purpose. For normal Timer operation (GATE1 = 0), setting TR1 allows TL1 to be incremented by the selected input. Setting GATE1 and TR1 allows external pin INT1# to control Timer operation. Timer 1 overflow (count rolls over from all 1s to all 0s) sets the TF1 flag generating an interrupt request. When Timer 0 is in mode 3, it uses Timer 1’s overflow flag (TF1) and run control bit (TR1). For this situation, use Timer 1 only for applications that do not require an interrupt (such as a Baud Rate Generator for the Serial Port) and switch Timer 1 in and out of mode 3 to turn it off and on. It is important to stop Timer/Counter before changing mode.
•
• •
• •
• Mode 0 (13-bit Timer)
Mode 0 configures Timer 1 as a 13-bit Timer, which is set up as an 8-bit Timer (TH1 register) with a modulo-32 prescaler implemented with the lower 5 bits of the TL1 register (see Figure 31). The upper 3 bits of TL1 register are ignored. Prescaler overflow increments TH1 register. Mode 1 configures Timer 1 as a 16-bit Timer with TH1 and TL1 registers connected in cascade (see Figure 32). The selected input increments TL1 register. Mode 2 configures Timer 1 as an 8-bit Timer (TL1 register) with automatic reload from TH1 register on overflow (see Figure 33). TL1 overflow sets TF1 flag in TCON register and reloads TL1 with the contents of TH1, which is preset by software. The reload leaves TH1 unchanged. Placing Timer 1 in mode 3 causes it to halt and hold its count. This can be used to halt Timer 1 when TR1 run control bit is not available i.e. when Timer 0 is in mode 3. Each Timer handles one interrupt source that is the timer overflow flag TF0 or TF1. This flag is set every time an overflow occurs. Flags are cleared when vectoring to the Timer interrupt routine. Interrupts are enabled by setting ETx bit in IEN0 register. This assumes interrupts are globally enabled by setting EA bit in IEN0 register.
Mode 1 (16-bit Timer)
Mode 2 (8-bit Timer with AutoReload)
Mode 3 (Halt)
Interrupt
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Figure 35. Timer Interrupt System
TF0
TCON.5
Timer 0 Interrupt Request ET0
IEN0.1
TF1
TCON.7
Timer 1 Interrupt Request ET1
IEN0.3
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Registers
Table 39. TCON Register TCON (S:88h) Timer/Counter Control Register
7 TF1 Bit Number 6 TR1 5 TF0 4 TR0 3 IE1 2 IT1 1 IE0 0 IT0
Bit Mnemonic Description Timer 1 Overflow Flag Cleared by hardware when processor vectors to interrupt routine. Set by hardware on Timer/Counter overflow, when Timer 1 register overflows. Timer 1 Run Control Bit Clear to turn off Timer/Counter 1. Set to turn on Timer/Counter 1. Timer 0 Overflow Flag Cleared by hardware when processor vectors to interrupt routine. Set by hardware on Timer/Counter overflow, when Timer 0 register overflows. Timer 0 Run Control Bit Clear to turn off Timer/Counter 0. Set to turn on Timer/Counter 0. Interrupt 1 Edge Flag Cleared by hardware when interrupt is processed if edge-triggered (see IT1). Set by hardware when external interrupt is detected on INT1# pin. Interrupt 1 Type Control Bit Clear to select low level active (level triggered) for external interrupt 1 (INT1#). Set to select falling edge active (edge triggered) for external interrupt 1. Interrupt 0 Edge Flag Cleared by hardware when interrupt is processed if edge-triggered (see IT0). Set by hardware when external interrupt is detected on INT0# pin. Interrupt 0 Type Control Bit Clear to select low level active (level triggered) for external interrupt 0 (INT0#). Set to select falling edge active (edge triggered) for external interrupt 0.
7
TF1
6
TR1
5
TF0
4
TR0
3
IE1
2
IT1
1
IE0
0
IT0
Reset Value = 0000 0000b
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Table 40. TMOD Register TMOD (S:89h) Timer/Counter Mode Control Register
7 GATE1 Bit Number 6 C/T1# 5 M11 4 M01 3 GATE0 2 C/T0# 1 M10 0 M00
Bit Mnemonic Description Timer 1 Gating Control Bit Clear to enable Timer 1 whenever TR1 bit is set. Set to enable Timer 1 only while INT1# pin is high and TR1 bit is set. Timer 1 Counter/Timer Select Bit Clear for Timer operation: Timer 1 counts the divided-down system clock. Set for Counter operation: Timer 1 counts negative transitions on external pin T1. Timer 1 Mode Select Bits M11 M01 Operating mode 0 0 Mode 0: 8-bit Timer/Counter (TH1) with 5-bit prescaler (TL1). 0 1 Mode 1: 16-bit Timer/Counter. 1 0 Mode 2: 8-bit auto-reload Timer/Counter (TL1)(1) 1 1 Mode 3: Timer 1 halted. Retains count Timer 0 Gating Control Bit Clear to enable Timer 0 whenever TR0 bit is set. Set to enable Timer/Counter 0 only while INT0# pin is high and TR0 bit is set. Timer 0 Counter/Timer Select Bit Clear for Timer operation: Timer 0 counts the divided-down system clock. Set for Counter operation: Timer 0 counts negative transitions on external pin T0. Timer 0 Mode Select Bit Operating mode M10 M00 0 0 Mode 0: 8-bit Timer/Counter (TH0) with 5-bit prescaler (TL0). 0 1 Mode 1: 16-bit Timer/Counter. 1 0 Mode 2: 8-bit auto-reload Timer/Counter (TL0)(2) 1 1 Mode 3: TL0 is an 8-bit Timer/Counter TH0 is an 8-bit Timer using Timer 1’s TR0 and TF0 bits.
7
GATE1
6
C/T1#
5
M11
4
M01
3
GATE0
2
C/T0#
1
M10
0
M00
Notes: 1. Reloaded from TH1 at overflow. 2. Reloaded from TH0 at overflow. Reset Value = 0000 0000b
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Table 41. TH0 Register TH0 (S:8Ch) Timer 0 High Byte Register
7 – Bit Number 7:0 6 – 5 – 4 – 3 – 2 – 1 – 0 –
Bit Mnemonic Description High Byte of Timer 0.
Reset Value = 0000 0000b Table 42. TL0 Register TL0 (S:8Ah) Timer 0 Low Byte Register
7 – Bit Number 7:0 6 – 5 – 4 – 3 – 2 – 1 – 0 –
Bit Mnemonic Description Low Byte of Timer 0.
Reset Value = 0000 0000b Table 43. TH1 Register TH1 (S:8Dh) Timer 1 High Byte Register
7 – Bit Number 7:0 6 – 5 – 4 – 3 – 2 – 1 – 0 –
Bit Mnemonic Description High Byte of Timer 1.
Reset Value = 0000 0000b
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Table 44. TL1 Register TL1 (S:8Bh) Timer 1 Low Byte Register
7 – Bit Number 7:0 6 – 5 – 4 – 3 – 2 – 1 – 0 –
Bit Mnemonic Description Low Byte of Timer 1.
Reset Value = 0000 0000b
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Timer 2
The A/T89C51AC2 timer 2 is compatible with timer 2 in the 80C52. It is a 16-bit timer/counter: the count is maintained by two eight-bit timer registers, TH2 and TL2 that are cascade- connected. It is controlled by T2CON register (See Table ) and T2MOD register (See Table 47). Timer 2 operation is similar to Timer 0 and Timer 1. C/T2 s elects F T2 clock/6 (timer operation) or external pin T2 (counter operation) as timer clock. Setting TR2 allows TL2 to be incremented by the selected input. Timer 2 includes the following enhancements: • • Auto-reload mode (up or down counter) Programmable clock-output
Auto-Reload Mode
The auto-reload mode configures timer 2 as a 16-bit timer or event counter with automatic reload. This feature is controlled by the DCEN bit in T2MOD register (See Table 47). Setting the DCEN bit enables timer 2 to count up or down as shown in Figure 36. In this mode the T2EX pin controls the counting direction. 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 overflow or underflow, depending on the direction of the count. EXF2 does not generate an interrupt. This bit can be used to provide 17-bit resolution.
Figure 36. Auto-Reload Mode Up/Down Counter
see section “Clock”
FT2 CLOCK :6 0 1
TR2
T2CON.2
CT/2
T2CON.1
T2 (DOWN COUNTING RELOAD VALUE) T2EX: FFh (8-bit) FFh
(8-bit)
1=UP 2=DOWN TOGGLE T2CONreg EXF2
TL2 (8-bit)
TH2 (8-bit)
TF2 T2CONreg
TIMER 2 INTERRUPT
RCAP2L (8-bit)
RCAP2H (8-bit)
(UP COUNTING RELOAD VALUE)
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Programmable ClockOutput
In clock-out mode, timer 2 operates as a 50%-duty-cycle, programmable clock generator (See Figure 37). The input clock increments TL2 at frequency FOSC /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 depending on the system oscillator frequency and the value in the RCAP2H and RCAP2L registers:
For a 16 MHz system clock in x1 mode, timer 2 has a programmable frequency range of 61 Hz (FOSC/216) to 4 MHz (FOSC/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 different depending on the application. To start the timer, set TR2 run control bit in T2CON register.
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 37. Clock-Out Mode
FT2 CLOCK
TR2
T2CON.2
Toggle T2 Q Q D T2OE T2MOD reg
T2EX EXEN2 T2CON reg
4127G–8051–05/06
– - ------------------------------------------- = - -------------------------------------------
4 × ( 65536
TL2 (8-bit)
RCAP2L RCAP2H (8-bit) (8-bit)
EXF2 T2CON reg
L P A CR H P A C R k co l c T F
2 ⁄
TH2 (8-bit) OVERFLOW TIMER 2 INTERRUPT
2
y c n euq e r F tuO – k co l C
2)
67
Registers
Table 45. T2CON Register T2CON (S:C8h) Timer 2 Control Register
7 TF2 Bit Number 6 EXF2 5 RCLK 4 TCLK 3 EXEN2 2 TR2 1 C/T2# 0 CP/RL2#
Bit Mnemonic Description Timer 2 Overflow Flag TF2 is not set if RCLK=1 or TCLK = 1. Must be cleared by software. Set by hardware on timer 2 overflow. Timer 2 External Flag Set when a capture or a reload is caused by a negative transition on T2EX pin if EXEN2=1. Set to cause the CPU to vector to timer 2 interrupt routine when timer 2 interrupt is enabled. Must be cleared by software. Receive Clock bit Clear 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 Clear 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 Clear 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 Clear to turn off timer 2. Set to turn on timer 2. Timer/Counter 2 Select bit Clear for timer operation (input from internal clock system: FOSC). Set for counter operation (input from T2 input pin). 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. Clear 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
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Table 46. T2MOD Register T2MOD (S:C9h) Timer 2 Mode Control Register
7 Bit Number 7 6 5 4 3 2 1 T2OE 0 DCEN
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 Clear 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 Clear to disable timer 2 as up/down counter. Set to enable timer 2 as up/down counter.
6
-
5
-
4
-
3
-
2
-
1
T2OE
0
DCEN
Reset Value = XXXX XX00b Not bit addressable Table 47. TH2 Register TH2 (S:CDh) Timer 2 High Byte Register
7 Bit Number 7-0 6 5 4 3 2 1 0 -
Bit Mnemonic Description High Byte of Timer 2.
Reset Value = 0000 0000b Not bit addressable
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Table 48. TL2 Register TL2 (S:CCh) Timer 2 Low Byte Register
7 Bit Number 7-0 6 5 4 3 2 1 0 -
Bit Mnemonic Description Low Byte of Timer 2.
Reset Value = 0000 0000b Not bit addressable Table 49. RCAP2H Register RCAP2H (S:CBh) Timer 2 Reload/Capture High Byte Register
7 Bit Number 7-0 6 5 4 3 2 1 0 -
Bit Mnemonic Description High Byte of Timer 2 Reload/Capture.
Reset Value = 0000 0000b Not bit addressable Table 50. RCAP2L Register RCAP2L (S:CAH) TIMER 2 R Eload/Capture Low Byte Register
7 Bit Number 7-0 6 5 4 3 2 1 0 -
Bit Mnemonic Description Low Byte of Timer 2 Reload/Capture.
Reset Value = 0000 0000b Not bit addressable
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A/T89C51AC2
Watchdog Timer
A/T89C51AC2 contains a powerful programmable hardware Watchdog Timer (WDT) that automatically resets the chip if it software fails to reset the WDT before the selected time interval has elapsed. It permits large Time-Out ranking from 16ms to 2s @Fosc = 12MHz in X1 mode. This WDT consists of a 14-bit counter plus a 7-bit programmable counter, a Watchdog Timer reset register (WDTRST) and a Watchdog Timer programming (WDTPRG) register. When exiting reset, the WDT is -by default- disable. To enable the WDT, the user has to write the sequence 1EH and E1H into WDTRST register no instruction in between. When the Watchdog Timer 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 generate an output RESET pulse at the RST pin. The RESET pulse duration is 96xTOSC, where TOSC=1/FOSC. 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
Note: When the Watchdog is enable it is impossible to change its period.
Figure 38. Watchdog Timer
RESET WR
Decoder
Control WDTRST
Enable 14-bit COUNTER Fwd Clock WDTPRG Outputs 7-bit COUNTER
4127G–8051–05/06
0
1
2
-
-
-
-
-
RESET
71
Watchdog Programming
The three lower bits (S0, S1, S2) located into WDTPRG register permit to program the WDT duration. Table 51. Machine Cycle Count
S2 0 0 0 0 1 1 1 1 S1 0 0 1 1 0 0 1 1 S0 0 1 0 1 0 1 0 1 Machine Cycle Count 214 - 1 215 - 1 216 - 1 217 - 1 218 - 1 219 - 1 220 - 1 221 - 1
To compute WD Time-Out, the following formula is applied:
Note:
Svalue represents the decimal value of (S2 S1 S0)
The following table outlines the time-out value for FoscXTAL = 12 MHz in X1 mode Table 52. Time-Out Computation
S2 0 0 0 0 1 1 1 1 S1 0 0 1 1 0 0 1 1 S0 0 1 0 1 0 1 0 1 Fosc = 12 MHz 16.38 ms 32.77 ms 65.54 ms 131.07 ms 262.14 ms 524.29 ms 1.05 s 2.10 s Fosc = 16 MHz 12.28 ms 24.57 ms 49.14 ms 98.28 ms 196.56 ms 393.12 ms 786.24 ms 1.57 s Fosc = 20 MHz 9.82 ms 19.66 ms 39.32 ms 78.64 ms 157.28 ms 314.56 ms 629.12 ms 1.25 s
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- --------------------------------------------------------------------------
6×2
(2
×2
eu l avS
2∧ 2
X c so F
XD W
=
tu O em i T F
–
14
)
A/T89C51AC2
Watchdog Timer During Power-down Mode and Idle
In Power-down mode the oscillator stops, which means the WDT also stops. While in Power-down mode, the user does not need to service the WDT. There are 2 methods of exiting Power-down 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, the Watchdog is disabled. Exiting Power-down with an interrupt is significantly different. The interrupt shall be 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 for the interrupt used to exit Power-down. To ensure that the WDT does not overflow within a few states of exiting powerdown, it is best to reset the WDT just before entering powerdown. In the Idle mode, the oscillator continues to run. To prevent the WDT from resetting A/T89C51AC2 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. Register Table 53. WDTPRG Register WDTPRG (S:A7h) Watchdog Timer Duration Programming Register
7 – Bit Number 7 6 – 5 – 4 – 3 – 2 S2 1 S1 0 S0
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. Watchdog Timer Duration selection bit 2 Work in conjunction with bit 1 and bit 0. Watchdog Timer Duration selection bit 1 Work in conjunction with bit 2 and bit 0. Watchdog Timer Duration selection bit 0 Work in conjunction with bit 1 and bit 2.
6
-
5
-
4
-
3
-
2
S2
1
S1
0
S0
Reset Value = XXXX X000b
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Table 54. WDTRST Register WDTRST (S:A6h Write only) Watchdog Timer Enable Register
7 – Bit Number 7 6 – 5 – 4 – 3 – 2 – 1 – 0 –
Bit Mnemonic Description Watchdog Control Value
Reset Value = 1111 1111b
Note: The WDRST register is used to reset/enable the WDT by writing 1EH then E1H in sequence without instruction between these two sequences.
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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 of the following signals: • • • • • • • • PCA clock frequency/6 (see “clock” section) PCA clock frequency/2 Timer 0 overflow External input on ECI (P1.2) rising and/or falling edge capture, software timer, high-speed output, pulse width modulator.
Each compare/capture modules can be programmed in any one of the following modes:
Module 4 can also be programmed as a Watchdog timer. see the "PCA Watchdog Timer" section. When the compare/capture modules are programmed in 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/Os. These pins are listed below. If the port is not used for the PCA, it 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 16-bit Module 4 External I/O Pin P1.2/ECI P1.3/CEX0 P1.4/CEX1 P1.5/CEX2 P1.6/CEX3 P1.7/CEX4
PCA Timer
The PCA timer is a common time base for all five modules (see Figure 39). The timer count source is determined from the CPS1 and CPS0 bits in the CMOD SFR (see Table 8) and can be programmed to run at: • • • • 1/6 the PCA clock frequency. 1/2 the PCA clock frequency. the Timer 0 overflow. the input on the ECI pin (P1.2).
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Figure 39. PCA Timer/Counter
To PCA modules FPca/6 FPca/2 T0 OVF P1.2 CH CL 16 bit up counter overflow It
CIDL Idle
WDTE
CPS1 CPS0
ECF
CMOD 0xD9
CF
CR
CCF4 CCF3 CCF2 CCF1 CCF0
CCON 0xD8
The CMOD register includes three additional bits associated with the PCA. • • • 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. The ECF bit which when set causes an interrupt and the PCA overflow flag CF in CCON register to be set when the PCA timer overflows.
The CCON register contains the run control bit for the PCA and the flags for the PCA timer and each module. • • • The CR bit must be set to run the PCA. The PCA is shut off by clearing this bit. The CF bit is set when the PCA counter overflows and an interrupt will be generated if the ECF bit in CMOD register is set. The CF bit can only be cleared by software. The CCF0:4 bits are the flags for the modules (CCF0 for module0...) and are set by hardware when either a match or a capture occurs. These flags also can be cleared by software.
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.
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Each module in the PCA has a special function register associated with it (CCAPM0 for module 0...). The CCAPM0:4 registers contain the bits that control the mode that each module will operate in. • • • The ECCF bit enables the CCF flag in the CCON register to generate an interrupt when a match or compare occurs in the associated module. The PWM bit enables the pulse width modulation mode. The TOG bit when set causes the CEX output associated with the module to toggle when there is a match between the PCA counter and the module’s capture/compare register. The match bit MAT 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 module’s capture/compare register. The two bits CAPN and CAPP in CCAPMn register 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. The bit ECOM in CCAPM register when set enables the comparator function.
•
•
•
PCA Interrupt
Figure 40. PCA Interrupt System
CF PCA Timer/Counter CR CCF4 CCF3 CCF2 CCF1 CCF0 CCON
Module 0
Module 1
To Interrupt
Module 2
Module 3
Module 4
ECF
CMOD.0
ECCFn
CCAPMn.0
EC
IEN0.6
EA
IEN0.7
PCA Capture Mode
To use one of the PCA modules in 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.
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Figure 41. PCA Capture Mode PCA Counter
CH CL (8bits) (8bits)
CEXn n = 0, 4
CCAPnH CCAPnL
CCFn CCON 7
PCA Interrupt Request
0CAPPn CAPNn
000
ECCFn
0 CCAPMn Register (n = 0, 4)
16-bit Software Timer 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.
Figure 42. PCA 16-bit Software Timer and High Speed Output Mode
PCA Counter CH CL (8 bits) (8 bits) Compare/Capture Module CCAPnL CCAPnH (8 bits) (8 bits) Match 16-Bit Comparator Enable CCFn CCON reg Toggle CEXn PCA Interrupt Request
ECOMn0 0 MATn TOGn0 ECCFn 0 CCAPMn Register (n = 0, 4) For software Timer mode, set ECOMn and MATn. For high speed output mode, set ECOMn, MATn and TOGn.
7 “0” Reset Write to CCAPnL Write to CCAPnH “1”
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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 module’s capture registers. To activate this mode the TOG, MAT, and ECOM bits in the module’s CCAPMn SFR must be set. Figure 43. PCA High Speed Output Mode
CCON CF Write to CCAPnH Write to CCAPnL “0” “1” Reset PCA IT CCAPnH Enable 16-bit comparator CCAPnL Match CR CCF4 CCF3 CCF2 CCF1 CCF0 0xD8
CH
CL
CEXn
PCA counter/timer CCAPMn, n = 0 to 4 0xDA to 0xDE
ECOMn CAPPn CAPNn MATn TOGn PWMn ECCFn
Pulse Width Modulator Mode
All the PCA modules can be used as PWM outputs. The output frequency depends on the source for the PCA timer. All the modules will have the same output frequency because they all share the PCA timer. The duty cycle of each module is independently variable using the module’s capture register CCAPLn. When the value of the PCA CL SFR is less than the value in the module’s CCAPLn SFR the output will be low, when it is equal to or greater than it, the output will be high. When CL overflows from FF to 00, CCAPLn is reloaded with the value in CCAPHn. the allows the PWM to be updated without glitches. The PWM and ECOM bits in the module’s CCAPMn register must be set to enable the PWM mode.
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Figure 44. PCA PWM Mode CCAPnH
CL rolls over from FFh TO 00h loads CCAPnH contents into CCAPnL
CCAPnL “0” CL < CCAPnL CL (8 bits) 8-Bit Comparator CEX CL > = CCAPnL “1”
ECOMn
CCAPMn.6
PWMn
CCAPMn.1
PCA Watchdog Timer
An on-board Watchdog timer is available with the PCA to improve system reliability without increasing chip count. Watchdog timers are useful for systems that are sensitive 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. 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. To hold off the reset, the user has three options: • • • periodically change the compare value so it will never match the PCA timer, periodically change the PCA timer value so it will never match the compare values, or disable the Watchdog by clearing the WDTE bit before a match occurs and then reenable it.
The first two options are more reliable because the Watchdog timer is never disabled as in the third option. If the program counter ever goes astray, a match will eventually occur and cause an internal reset. If other PCA modules are being used the second option not recommended either. 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.
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PCA Registers
Table 55. CMOD Register CMOD (S:D9h) PCA Counter Mode Register
7 CIDL Bit Number 6 WDTE 5 4 3 2 CPS1 1 CPS0 0 ECF
Bit Mnemonic Description PCA Counter Idle Control bit Clear to let the PCA run during Idle mode. Set to stop the PCA when Idle mode is invoked. Watchdog Timer Enable Clear to disable Watchdog Timer function on PCA Module 4, Set to enable it. 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. EWC Count Pulse Select bits CPS1 CPS0 Clock source 0 0 Internal Clock, FPca/6 0 1 Internal Clock, FPca/2 1 0 Timer 0 overflow 1 1 External clock at ECI/P1.2 pin (Max. Rate = FPca/4) Enable PCA Counter Overflow Interrupt bit Clear to disable CF bit in CCON register to generate an interrupt. Set to enable CF bit in CCON register to generate an interrupt.
7
CIDL
6
WDTE
5
-
4
-
3
-
2-1
CPS1:0
0
ECF
Reset Value = 00XX X000b
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Table 56. CCON Register CCON (S:D8h) PCA Counter Control Register
7 CF Bit Number 6 CR 5 4 CCF4 3 CCF3 2 CCF2 1 CCF1 0 CCF0
Bit Mnemonic Description PCA Timer/Counter Overflow flag Set by hardware when the PCA Timer/Counter rolls over. This generates a PCA interrupt request if the ECF bit in CMOD register is set. Must be cleared by software. PCA Timer/Counter Run Control bit Clear to turn the PCA Timer/Counter off. Set to turn the PCA Timer/Counter on. Reserved The value read from this bit is indeterminate. Do not set this bit. PCA Module 4 Compare/Capture flag Set by hardware when a match or capture occurs. This generates a PCA interrupt request if the ECCF 4 bit in CCAPM 4 register is set. Must be cleared by software. PCA Module 3 Compare/Capture flag Set by hardware when a match or capture occurs. This generates a PCA interrupt request if the ECCF 3 bit in CCAPM 3 register is set. Must be cleared by software. PCA Module 2 Compare/Capture flag Set by hardware when a match or capture occurs. This generates a PCA interrupt request if the ECCF 2 bit in CCAPM 2 register is set. Must be cleared by software. PCA Module 1 Compare/Capture flag Set by hardware when a match or capture occurs. This generates a PCA interrupt request if the ECCF 1 bit in CCAPM 1 register is set. Must be cleared by software. PCA Module 0 Compare/Capture flag Set by hardware when a match or capture occurs. This generates a PCA interrupt request if the ECCF 0 bit in CCAPM 0 register is set. Must be cleared by software.
7
CF
6
CR
5
-
4
CCF4
3
CCF3
2
CCF2
1
CCF1
0
CCF0
Reset Value = 00X0 0000b
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Table 57. CCAPnH Registers CCAP0H (S:FAh) CCAP1H (S:FBh) CCAP2H (S:FCh) CCAP3H (S:FDh) CCAP4H (S:FEh) PCA High Byte Compare/Capture Module n Register (n=0..4)
7 CCAPnH 7 Bit Number 7:0 6 CCAPnH 6 5 CCAPnH 5 4 CCAPnH 4 3 CCAPnH 3 2 CCAPnH 2 1 CCAPnH 1 0 CCAPnH 0
Bit Mnemonic Description CCAPnH 7:0 High byte of EWC-PCA comparison or capture values
Reset Value = 0000 0000b Table 58. CCAPnL Registers CCAP0L (S:EAh) CCAP1L (S:EBh) CCAP2L (S:ECh) CCAP3L (S:EDh) CCAP4L (S:EEh) PCA Low Byte Compare/Capture Module n Register (n=0..4)
7 CCAPnL 7 Bit Number 7:0 6 CCAPnL 6 5 CCAPnL 5 4 CCAPnL 4 3 CCAPnL 3 2 CCAPnL 2 1 CCAPnL 1 0 CCAPnL 0
Bit Mnemonic Description CCAPnL 7:0 Low byte of EWC-PCA comparison or capture values
Reset Value = 0000 0000b
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Table 59. CCAPMn Registers CCAPM0 (S:DAh) CCAPM1 (S:DBh) CCAPM2 (S:DCh) CCAPM3 (S:DDh) CCAPM4 (S:DEh) PCA Compare/Capture Module n Mode registers (n=0..4)
7 Bit Number 7 6 ECOMn 5 CAPPn 4 CAPNn 3 MATn 2 TOGn 1 PWMn 0 ECCFn
Bit Mnemonic Description Reserved The Value read from this bit is indeterminate. Do not set this bit. Enable Compare Mode Module x bit Clear to disable the Compare function. Set to enable the Compare function. The Compare function is used to implement the software Timer, the high-speed output, the Pulse Width Modulator (PWM) and the Watchdog Timer (WDT). Capture Mode (Positive) Module x bit Clear to disable the Capture function triggered by a positive edge on CEXx pin. Set to enable the Capture function triggered by a positive edge on CEXx pin Capture Mode (Negative) Module x bit Clear to disable the Capture function triggered by a negative edge on CEXx pin. Set to enable the Capture function triggered by a negative edge on CEXx pin. Match Module x bit Set when a match of the PCA Counter with the Compare/Capture register sets CCFx bit in CCON register, flagging an interrupt. Toggle Module x bit The toggle mode is configured by setting ECOMx, MATx and TOGx bits. Set when a match of the PCA Counter with the Compare/Capture register toggles the CEXx pin. Pulse Width Modulation Module x Mode bit Set to configure the module x as an 8-bit Pulse Width Modulator with output waveform on CEXx pin. Enable CCFx Interrupt bit Clear to disable CCFx bit in CCON register to generate an interrupt request. Set to enable CCFx bit in CCON register to generate an interrupt request.
6
ECOMn
5
CAPPn
4
CAPNn
3
MATn
2
TOGn
1
PWMn
0
ECCFn
Reset Value = X000 0000b
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Table 60. CH Register CH (S:F9h) PCA Counter Register High Value
7 CH 7 Bit Number 7:0 6 CH 6 5 CH 5 4 CH 4 3 CH 3 2 CH 2 1 CH 1 0 CH 0
Bit Mnemonic Description CH 7:0 High byte of Timer/Counter
Reset Value = 0000 00000b Table 61. CL Register CL (S:E9h) PCA counter Register Low Value
7 CL 7 Bit Number 7:0 6 CL 6 5 CL 5 4 CL 4 3 CL 3 2 CL 2 1 CL 1 0 CL 0
Bit Mnemonic Description CL0 7:0 Low byte of Timer/Counter
Reset Value = 0000 00000b
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Analog-to-Digital Converter (ADC)
Th is se ction de scribe s the on -chip 10 bit an alog -to-d ig ita l c onv erte r of th e A/T89C51AC2. Eight ADC channels are available for sampling of the external sources AN0 to AN7. An analog multiplexer allows the single ADC converter to select one from the 8 ADC channels as ADC input voltage (ADCIN). ADCIN is converted by the 10-bit cascaded potentiometric ADC. Two modes of conversion are available: - Standard conversion (8 bits). - Precision conversion (10 bits). For the precision conversion, set bit PSIDLE in ADCON register and start conversion. The device is in a pseudo-idle mode, the CPU does not run but the peripherals are always running. This mode allows digital noise to be as low as possible, to ensure high precision conversion. For this mode it is necessary to work with end of conversion interrupt, which is the only way to wake the device up. If another interrupt occurs during the precision conversion, it will be served only after this conversion is completed.
Features
• • • • • • • • • •
8 channels with multiplexed inputs 10-bit cascaded potentiometric ADC Conversion time 16 micro-seconds (typ.) Zero Error (offset) ± 2 LSB max Positive External Reference Voltage Range (VAREF) 2.4 to 3.0 Volt (typ.) ADCIN Range 0 to 3Volt Integral non-linearity typical 1 LSB, max. 2 LSB Differential non-linearity typical 0.5 LSB, max. 1 LSB Conversion Complete Flag or Conversion Complete Interrupt Selectable ADC Clock
ADC Port 1 I/O Functions Port 1 pins are general I/O that are shared with the ADC channels. The channel select
bit in ADCF register define which ADC channel/port1 pin will be used as ADCIN. The remaining ADC channels/port1 pins can be used as general-purpose I/O or as the alternate function that is available. A conversion launched on a channel which are not selected on ADCF register will not have any effect.
VAREF
VAREF should be connected to a low impedance point and must remain in the range specified in Table 77. If the ADC is not used, it is recommended to connect VAREF to VAGND.
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Figure 45. ADC Description
ADCON.5 ADCON.3
ADEN
ADSST
ADCON.4
ADC CLOCK
ADEOC
CONTROL
ADC Interrupt Request EADC
IEN1.1
AN0/P1.0 AN1/P1.1 AN2/P1.2 AN3/P1.3 AN4/P1.4 AN5/P1.5 AN6/P1.6 AN7/P1.7
000 001 010 011 100 101 110 111
Cai Rai
ADCIN
8
+ SAR 2
ADDH ADDL
AVSS
Sample and Hold R/2R DAC
10
SCH2
ADCON.2
SCH1
ADCON.1
SCH0
ADCON.0
VAREF VAGND
Figure 46 shows the timing diagram of a complete conversion. For simplicity, the figure depicts the waveforms in idealized form and do not provide precise timing information. For ADC characteristics and timing parameters refer to the Section “AC Characteristics” of the A/T89C51AC2 datasheet. Figure 46. Timing Diagram CLK ADEN
TSETUP (1)
ADSST
TCONV (2)
ADEOC
Notes:
1. Tsetup min, see the AC Parameter for A/D conversion. 2. Tconv = 11 clock ADC = 1sample and hold + 10 bit conversion The user must ensure that Tsetup time between setting ADEN and the start of the first conversion.
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ADC Converter Operation
A start of single A/D conversion is triggered by setting bit ADSST (ADCON.3). After completion of the A/D conversion, the ADSST bit is cleared by hardware. The end-of-conversion flag ADEOC (ADCON.4) is set when the value of conversion is available in ADDH and ADDL, it must be cleared by software. If the bit EADC (IEN1.1) is set, an interrupt occur when flag ADEOC is set (see Figure 48). Clear this flag for rearming the interrupt. The bits SCH0 to SCH2 in ADCON register are used for the analog input channel selection.(1)
Note: 1. Always leave Tsetup time before starting a conversion unless ADEN is permanently high. In this case one should wait Tsetup only before the first conversion.
Table 62. Selected Analog input
SCH2 0 0 0 0 1 1 1 1 SCH1 0 0 1 1 0 0 1 1 SCH0 0 1 0 1 0 1 0 1 Selected Analog input AN0 AN1 AN2 AN3 AN4 AN5 AN6 AN7
Voltage Conversion
When the ADCIN is equals to VAREF the ADC converts the signal to 3FFh (full scale). If the input voltage equals VAGND, the ADC converts it to 000h. Input voltage between VAREF and VAGND are a straight-line linear conversion. All other voltages will result in 3FFh if greater than VAREF and 000h if less than VAGND.
Note: ADCIN should not exceed VAREF absolute maximum range (see “Absolute Maximum Ratings” on page 141)
Clock Selection
The ADC clock is the same as CPU. The maximum clock frequency is defined in the DC parmeter for A/D converter. A prescaler is featured (ADCCLK) to generate the ADC clock from the oscillator frequency. if PRS > 0 then fADC = Fperiph / 2 x PRS if PRS = 0 then fADC = Fperiph / 64
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Figure 47. A/D Converter clock
CPU CLOCK
÷2
Prescaler ADCLK
ADC Clock
A/D Converter
CPU Core Clock Symbol
ADC Standby Mode IT ADC Management
When the ADC is not used, it is possible to set it in standby mode by clearing bit ADEN in ADCON register. In this mode its power dissipation is reduced. An interrupt end-of-conversion will occurs when the bit ADEOC is activated and the bit EADC is set. For re-arming the interrupt the bit ADEOC must be cleared by software. Figure 48. ADC Interrupt Structure
ADEOC
ADCON.2
ADCI EADC
IEN1.1
Routines examples
1. Configure P1.2 and P1.3 in ADC channels
// configure channel P1.2 and P1.3 for ADC ADCF = 0Ch // Enable the ADC ADCON = 20h
2. Start a standard conversion
// The variable "channel" contains the channel to convert // The variable "value_converted" is an unsigned int // Clear the field SCH[2:0] ADCON and = F8h // Select channel ADCON | = channel // Start conversion in standard mode ADCON | = 08h // Wait flag End of conversion while((ADCON and 01h)! = 01h) // Clear the End of conversion flag ADCON and = EFh // read the value value_converted = (ADDH
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