Features |
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• Compatible with MCS-51™ Products |
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• 4K Bytes of User Programmable QuickFlash™ Memory |
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• Fully Static Operation: 0 Hz to 24 MHz |
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• Three-Level Program Memory Lock |
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• 128 x 8-Bit Internal RAM |
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• 32 Programmable I/O Lines |
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• |
Two 16-Bit Timer/Counters |
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Six Interrupt Sources |
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Programmable Serial Channel |
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8-Bit |
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• Low Power Idle and Power Down Modes |
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Description |
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Microcontroller |
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The AT87F51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K |
with 4K Bytes |
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bytes of QuickFlash Programmable Read Only Memory. The device is manufactured |
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using Atmel’s high density nonvolatile memory technology and is compatible with the |
QuickFlash™ |
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industry standard MCS-51™ instruction set and pinout. The on-chip QuickFlash |
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allows the program memory to be user programmed by a conventional nonvolatile |
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memory programmer. By combining a versatile 8-bit CPU with QuickFlash on a mono- |
AT87F51 |
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lithic chip, the Atmel AT87F51 is a powerful microcomputer which provides a highly |
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flexible and cost effective solution to many embedded control applications. |
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(continued) |
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Pin Configurations |
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PDIP |
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P 1 . 0 |
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1 |
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4 0 |
V C C |
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P 1 . 1 |
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2 |
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3 9 |
P 0 . 0 ( A D 0 ) |
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P 1 . 2 |
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3 |
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3 8 |
P 0 . 1 ( A D 1 ) |
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P 1 . 3 |
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4 |
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3 7 |
P 0 . 2 ( A D 2 ) |
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P 1 . 4 |
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5 |
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3 6 |
P 0 . 3 ( A D 3 ) |
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P 1 . 5 |
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6 |
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3 5 |
P 0 . 4 ( A D 4 ) |
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P 1 . 6 |
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7 |
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3 4 |
P 0 . 5 ( A D 5 ) |
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P 1 . 7 |
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3 3 |
P 0 . 6 ( A D 6 ) |
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R S T |
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9 |
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3 2 |
P 0 . 7 ( A D 7 ) |
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8TQFP |
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( R X D ) P 3 . 0 |
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1 0 |
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3 1 E A / V P P |
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( T X D ) P 3 . 1 |
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1 1 |
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3 0 A L E / P R O G |
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) ) ) ) |
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( I N T 0 ) P 3 . 2 |
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1 2 |
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2 9 |
P S E N |
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D0 D1 D2 D3 |
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( I N T 1 ) P 3 . 3 |
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1 3 |
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2 8 |
P 2 . 7 ( A 1 5 ) |
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I N D E X |
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(A (A (A (A |
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( T 0 ) P 3 . 4 |
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1 4 |
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2 7 |
P 2 . 6 ( A 1 4 ) |
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1.4 1.3 1.2 1.1 1.0 C |
CC |
0.0 0.1 0.2 0.3 |
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( T 1 ) P 3 . 5 |
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1 5 |
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2 6 |
P 2 . 5 ( A 1 3 ) |
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C O R N E R |
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( W R ) P 3 . 6 |
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1 6 |
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2 5 |
P 2 . 4 ( A 1 2 ) |
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P P P P P N |
V |
P P P P |
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( R D ) P 3 . 7 |
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1 7 |
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2 4 |
P 2 . 3 ( A 1 1 ) |
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4 4 |
4 2 |
4 0 |
3 8 |
3 6 |
3 4 |
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X TA L 2 |
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1 8 |
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2 3 |
P 2 . 2 ( A 1 0 ) |
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X TA L 1 |
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1 9 |
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2 2 |
P 2 . 1 ( A 9 ) |
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4 3 |
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4 1 3 9 |
3 7 3 5 |
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P 1 . 5 |
1 |
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3 3 |
P 0 . 4 ( A D 4 ) |
G N D |
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2 0 |
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2 1 |
P 2 . 0 ( A 8 ) |
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P 1 . 6 |
2 |
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3 2 |
P 0 . 5 ( A D 5 ) |
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PLCC |
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P 1 . 7 |
3 |
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3 1 |
P 0 . 6 ( A D 6 ) |
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R S T |
4 |
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3 0 |
P 0 . 7 ( A D 7 ) |
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0) 1) 2) 3) |
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( R X D ) P 3 . 0 |
5 |
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2 9 |
E A / V P P |
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N C |
6 |
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2 8 |
N C |
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D D D D |
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(A (A (A (A |
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( T X D ) P 3 . 1 |
7 |
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2 7 |
A L E / P R O G |
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( I N T 0 ) P 3 . 2 |
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2 6 |
P S E N |
I N D E X |
1P.4 |
1P.3 1P.2 1P.1 1P.0 CN |
CVC |
0P.0 0P.1 0P.2 0P.3 |
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( T 0 ) P 3 . 4 |
1 0 |
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2 4 |
P 2 . 6 ( A 1 4 ) |
C O R N E R |
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( I N T 1 ) P 3 . 3 |
9 |
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2 5 |
P 2 . 7 ( A 1 5 ) |
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( T 1 ) P 3 . 5 |
1 1 |
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2 3 |
P 2 . 5 ( A 1 3 ) |
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4 |
2 |
4 4 |
4 2 |
4 0 |
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1 9 |
2 12 2 |
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P 1 . 5 |
7 |
5 |
3 |
1 |
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4 3 4 13 9 |
P 0 . 4 ( A D 4 ) |
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1 21 31 41 51 61 71 8 2 0 |
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.3P6 .3P7 LTA2 LTA1 DNG DNG .2P0 .2P1 .2P2 .2P3 .2P4 |
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P 1 . 6 |
8 |
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3 8 |
P 0 . 5 ( A D 5 ) |
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P 1 . 7 |
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3 7 |
P 0 . 6 ( A D 6 ) |
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R S T 1 0 |
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3 6 |
P 0 . 7 ( A D 7 ) |
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) ) X X |
) ) ) ) ) |
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( R X D ) P 3 . 0 |
1 1 |
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3 5 E A / V P P |
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RW( DR( |
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8A( 9A( 01A( 11A( 21A( |
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N C |
1 2 |
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3 4 |
N C |
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( T X D ) P 3 . 1 |
1 3 |
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3 3 A L E / P R O G |
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( I N T 0 ) P 3 . 2 |
1 4 |
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3 2 P S E N |
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( I N T 1 ) P 3 . 3 |
1 5 |
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3 1 |
P 2 . 7 ( A 1 5 ) |
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( T 0 ) P 3 . 4 |
1 6 |
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3 0 |
P 2 . 6 ( A 1 4 ) |
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( T 1 ) P 3 . 5 |
1 7 |
1 9 2 1 |
2 3 |
2 5 2 72 9 |
P 2 . 5 ( A 1 3 ) |
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1 8 |
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2 0 |
2 2 |
2 4 |
2 6 |
2 8 |
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P3.6 P3.7 TAL2 TAL1 GND NC P2.0 P2.1 P2.2 P2.3 P2.4 |
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RW() DR() X X |
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8A() 9A() 01A() 11A() 21A() |
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Rev. 1012A–02/98 |
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1 |
Block Diagram |
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P0.0 |
- P0.7 |
P2.0 |
- P2.7 |
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VCC |
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PORT 0 DRIVERS |
PORT 2 DRIVERS |
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GND |
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RAM ADDR. |
RAM |
PORT 0 |
PORT 2 |
QUICK |
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REGISTER |
LATCH |
LATCH |
FLASH |
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B |
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STACK |
PROGRAM |
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ACC |
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ADDRESS |
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REGISTER |
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POINTER |
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REGISTER |
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TMP2 |
TMP1 |
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BUFFER |
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PC |
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ALU |
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INCREMENTER |
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INTERRUPT, SERIAL PORT, |
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AND TIMER BLOCKS |
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PROGRAM |
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PSW |
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COUNTER |
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PSEN |
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ALE/PROG |
TIMING |
INSTRUCTION |
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DPTR |
AND |
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REGISTER |
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EA / VPP |
CONTROL |
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RST |
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PORT 1 |
PORT 3 |
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LATCH |
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LATCH |
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OSC |
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PORT 1 DRIVERS |
PORT 3 DRIVERS |
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P1.0 - P1.7 |
P3.0 |
- P3.7 |
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2 |
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AT87F51 |
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The AT87F51 provides the following standard features: 4K bytes of QuickFlash, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator and clock circuitry. In addition, the AT87F51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle M od e s to p s t he C P U w hi l e a l l ow i ng t he R A M , timer/counters, serial port and interrupt system to continue functioning. The Power Down Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset.
Pin Description
VCC
Supply voltage.
GND
Ground.
Port 0
Port 0 is an 8-bit open drain bidirectional I/O port. As an output port each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as highimpedance inputs.
Port 0 may also be configured to be the multiplexed loworder address/data bus during accesses to external program and data memory. In this mode P0 has internal pullups.
Port 0 also receives the code bytes during QuickFlash programming, and outputs the code bytes during program verification. External pullups are required during program verification.
Port 1
Port 1 is an 8-bit bidirectional I/O port with internal pullups. The Port 1 output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins they are pulled high by the internal pullups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pullups.
Port 1 also receives the low-order address bytes during QuickFlash programming and verification.
Port 2
Port 2 is an 8-bit bidirectional I/O port with internal pullups. The Port 2 output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins they are pulled high by the internal pullups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pullups.
Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses (MOVX @ DPTR). In this application it uses strong internal pullups
AT87F51
when emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register.
Port 2 also receives the high-order address bits and some control signals during QuickFlash programming and verification.
Port 3
Port 3 is an 8-bit bidirectional I/O port with internal pullups. The Port 3 output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins they are pulled high by the internal pullups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL) because of the pullups.
Port 3 also serves the functions of various special features of the AT87F51 as listed below:
Port Pin |
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P3.0 |
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RXD (serial input port) |
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P3.1 |
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TXD (serial output port) |
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P3.2 |
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(external interrupt 0) |
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INT0 |
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P3.3 |
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(external interrupt 1) |
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INT1 |
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P3.4 |
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T0 (timer 0 external input) |
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P3.5 |
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T1 (timer 1 external input) |
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P3.6 |
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(external data memory write strobe) |
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WR |
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P3.7 |
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(external data memory read strobe) |
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RD |
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Port 3 also receives some control signals for QuickFlash programming and verification.
RST
Reset input. A high on this pin for two machine cycles while the oscillator is running resets the device.
ALE/PROG
Address Latch Enable output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input (PROG) during QuickFlash programming.
In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency, and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped during each access to external Data Memory.
If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode.
PSEN
Program Store Enable is the read strobe to external program memory.
3
When the AT87F51 is executing code from external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory.
EA/VPP
External Access Enable. EA must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset.
EA should be strapped to VCC for internal program executions.
This pin also receives the 12-volt programming enable voltage (VPP) during QuickFlash programming.
XTAL1
Input to the inverting oscillator amplifier and input to the internal clock operating circuit.
XTAL2
Output from the inverting oscillator amplifier.
Oscillator Characteristics
XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier which can be configured for use as an on-chip oscillator, as shown in Figure 1. Either a quartz crystal or ceramic resonator may be used. To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1 is driven as shown in Figure 2. There are no requirements on the duty cycle of the external clock signal, since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high and low time specifications must be observed.
It should be noted that when idle is terminated by a hard ware reset, the device normally resumes program execution, from where it left off, up to two machine cycles before the internal reset algorithm takes control. On-chip hardware inhibits access to internal RAM in this event, but access to the port pins is not inhibited. To eliminate the possibility of an unexpected write to a port pin when Idle is terminated by reset, the instruction following the one that invokes Idle should not be one that writes to a port pin or to external memory.
Figure 1. Oscillator Connections
C2
XTAL2
C1
XTAL1
GND
Note: C1, C2 = 30 pF ± 10 pF for Crystals
= 40 pF ± 10 pF for Ceramic Resonators
Figure 2. External Clock Drive Configuration
Idle Mode
In idle mode, the CPU puts itself to sleep while all the onchip peripherals remain active. The mode is invoked by software. The content of the on-chip RAM and all the special functions registers remain unchanged during this mode. The idle mode can be terminated by any enabled interrupt or by a hardware reset.
Status of External Pins During Idle and Power Down Modes
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Mode |
Program Memory |
ALE |
PSEN |
PORT0 |
PORT1 |
PORT2 |
PORT3 |
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Idle |
Internal |
1 |
1 |
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Data |
Data |
Data |
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Idle |
External |
1 |
1 |
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Float |
Data |
Address |
Data |
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Power Down |
Internal |
0 |
0 |
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Data |
Data |
Data |
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Power Down |
External |
0 |
0 |
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Float |
Data |
Data |
Data |
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4 |
AT87F51 |
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Power Down Mode
In the power down mode the oscillator is stopped, and the instruction that invokes power down is the last instruction executed. The on-chip RAM and Special Function Registers retain their values until the power down mode is terminated. The only exit from power down is a hardware reset. Reset redefines the SFRs but does not change the on-chip RAM. The reset should not be activated before VCC is restored to its normal operating level and must be held active long enough to allow the oscillator to restart and stabilize.
AT87F51
Program Memory Lock Bits
On the chip are three lock bits which can be left unprogrammed (U) or can be programmed (P) to obtain the additional features listed in the table below:
When lock bit 1 is programmed, the logic level at the EA pin is sampled and latched during reset. If the device is powered up without a reset, the latch initializes to a random value, and holds that value until reset is activated. It is necessary that the latched value of EA be in agreement with the current logic level at that pin in order for the device to function properly.
Lock Bit Protection Modes
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Program Lock Bits |
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Protection Type |
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LB1 |
LB2 |
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LB3 |
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1 |
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U |
U |
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U |
No program lock features. |
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2 |
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P |
U |
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U |
MOVC instructions executed from external program memory are disabled from fetching code |
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bytes from internal memory, |
EA |
is sampled and latched on reset, and further programming of the |
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QuickFlash is disabled. |
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3 |
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P |
P |
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U |
Same as mode 2, also verify is disabled. |
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4 |
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P |
P |
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P |
Same as mode 3, also external execution is disabled. |
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Programming the QuickFlash
The AT87F51 is shipped with the on-chip QuickFlash memory array ready to be programmed. The programming interface needs a high-voltage (12-volt) program enable signal and is compatible with conventional third-party Flash or EPROM programmers.
The AT87F51 code memory array is programmed byte-by- byte.
Programming Algorithm: Before programming the AT87F51, the address, data, and control signals should be set up according to the QuickFlash programming mode table and Figures 3 and 4. To program the AT87F51, take the following steps:
1.Input the desired memory location on the address lines.
2.Input the appropriate data byte on the data lines.
3.Activate the correct combination of control signals.
4.Raise EA/VPP to 12V.
5.Pulse ALE/PROG once to program a byte in the QuickFlash array or the lock bits. The byte-write cycle is selftimed and typically takes no more than 1.5 ms. Repeat steps 1 through 5, changing the address and data for the entire array or until the end of the object file is reached.
Data Polling: The AT87F51 features Data Polling to indicate the end of a write cycle. During a write cycle, an attempted read of the last byte written will result in the complement of the written datum on PO.7. Once the write cycle
has been completed, true data are valid on all outputs, and the next cycle may begin. Data Polling may begin any time after a write cycle has been initiated.
Ready/Busy: The progress of byte programming can also be monitored by the RDY/BSY output signal. P3.4 is pulled low after ALE goes high during programming to indicate BUSY. P3.4 is pulled high again when programming is done to indicate READY.
Program Verify: If lock bits LB1 and LB2 have not been programmed, the programmed code data can be read back via the address and data lines for verification. The lock bits cannot be verified directly. Verification of the lock bits is achieved by observing that their features are enabled.
Reading the Signature Bytes: The signature bytes are read by the same procedure as a normal verification of locations 030H, 031H, and 032H, except that P3.6 and P3.7 must be pulled to a logic low. The values returned are as follows.
(030H) = 1EH indicates manufactured by Atmel
(031H) = 87H indicates 87F family
(032H) = 01H indicates 87F51
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