8051 Atmel AT89C51 Microcontroller
8051 Atmel AT89C51 Microcontroller is an 8-bit microcontroller and belongs to Atmels 8051 families. ATMEL 89C51 has 4KB of Flash programmable and erasable read-only memory (PEROM) and 128 bytes of RAM. It can be erased and program to a maximum of 1000 times.
In 40 pin AT89C51, there are four ports designated as P1, P2, P3, and P0. All these ports are 8-bit bi-directional ports i.e., they can be used as both input and output ports. Except for P0 which needs external pull-ups, the rest of the ports have internal pull-ups. When 1s are written to these port pins, they are pulled high by the internal pull-ups and can be used as inputs. These ports are also a bit addressable and so their bits can also be accessed individually.
Port P0 and P2 are also used to provide low byte and high byte addresses, respectively, when connected to external memory. Port 3 has multiplexed pins for special functions like serial communication, hardware interrupts, timer inputs, and read/write operation from external memory. AT89C51 has an inbuilt UART for serial communication. It can be programmed to operate at different baud rates. Including two timers hard interrupts, it has a total of six interrupts.
Pin Description
| Pin Number | Pin Name | Description |
| 1 | P1.0 | 0th pin of PORT P1 |
| 2 | P1.1 | 1st pin of PORT P1 |
| 3 | P1.2 | 2nd pin of PORT P1 |
| 4 | P1.3 | 3rd pin of PORT P1 |
| 5 | P1.4 | 4th pin of PORT P1 |
| 6 | P1.5 | 5th pin of PORT P1 |
| 7 | P1.6 | 6th pin of PORT P1 |
| 8 | P1.7 | 7th pin of PORT P1 |
| 9 | RST | Reset pin of the Microcontroller |
| 10 | (RXD) P3.0 | 0th pin of PORT P3 or Receiver pin of Microcontroller |
| 11 | (TXD) P3.1 | 1st pin of PORT P3 or Transmitter pin of Microcontroller |
| 12 | (INT0) P3.2 | 2nd pin of PORT P3 or External Interrupt 0 of MCU |
| 13 | (INT1) P3.3 | 3rd pin of PORT P3 or External Interrupt 1 of MCU |
| 14 | (T0) P3.4 | 4th pin of PORT P3 or Timer 0 interrupt of MCU |
| 15 | (T1) P3.5 | 5th pin of PORT P3 or Timer 1 interrupt of MCU |
| 16 | (WR) P3.6 | 6th pin of PORT P3 or Write to External data memory pin |
| 17 | (RD) P3.7 | 7th pin of PORT P3 or Read from External data memory pin |
| 18 | XTAL2 | External crystal pin 2 of Microcontroller |
| 19 | XTAL1 | External crystal pin 1 of Microcontroller |
| 20 | GND | Ground pin of MCU |
| 21 | P2.0(A8) | 0th pin of PORT P2 or High-order Address bit 8 of MCU |
| 22 | P2.1(A9) | 1st pin of PORT P2 or High-order Address bit 9 of MCU |
| 23 | P2.2(A10) | 2nd pin of PORT P2 or High-order Address bit 10 of MCU |
| 24 | P2.3(A11) | 3rd pin of PORT P2 or High-order Address bit 11 of MCU |
| 25 | P2.4(A12) | 4th pin of PORT P2 or High-order Address bit 12 of MCU |
| 26 | P2.5(A13) | 5th pin of PORT P2 or High-order Address bit 13 of MCU |
| 27 | P2.6(A14) | 6th pin of PORT P2 or High-order Address bit 14 of MCU |
| 28 | P2.7(A15) | 7th pin of PORT P2 or High-order Address bit 15 of MCU |
| 29 | PSEN | Program store enable pin, Read external program memory |
| 30 | ALE/PROG | Address Latch Enable/ Program Pulse input for flashing |
| 31 | EA/VPP | Access Enable voltage/Program enable voltage |
| 32 | P0.7(AD7) | 7th pin of PORT P0 or Low-order Address bit 7 of MCU |
| 33 | P0.6(AD6) | 6th pin of PORT P0 or Low -order Address bit 6 of MCU |
| 34 | P0.5(AD5) | 6th pin of PORT P0 or Low -order Address bit 5 of MCU |
| 35 | P0.4(AD4) | 6th pin of PORT P0 or Low -order Address bit 4 of MCU |
| 36 | P0.3(AD3) | 3rd pin of PORT P0 or Low -order Address bit 3 of MCU |
| 37 | P0.2(AD2) | 2nd pin of PORT P0 or Low -order Address bit 2 of MCU |
| 38 | P0.1(AD1) | 1st pin of PORT P0 or Low -order Address bit 1 of MCU |
| 39 | P0.0(AD0) | 0th pin of PORT P0 or Low -order Address bit 0 of MCU |
| 40 | Vcc | Supply pin of MCU |
Features
| AT89C51 Simplified Features | |
| CPU | 8-bit 8051 |
| Number of Pins | 40 |
| Operating Voltage (V) | 2 to 5.5 V |
| Number of I/O pins | 32 |
| ADC Module | Nil |
| Timer/Counter Module | 16-bit(2) |
| Comparators | Nil |
| DAC Module | Nil |
| Communication Peripherals | UART(1) |
| External Oscillator | 3MHz to 24Mhz |
| Internal Oscillator | Yes |
| Program Memory Type | Flash |
| Program Memory (KB) | 4K |
| RAM Bytes | 128 8-bit |
| Data EEPROM | Nil |
Specification:
- Compatible with MCS-51 Products
- 4K Bytes of In-System Reprogrammable Flash Memory
- Endurance: 1,000 Write/Erase Cycles
- Fully Static Operation: 0 Hz to 24 MHz
- Three-Level Program Memory Lock
- 128 x 8-Bit Internal RAM
- 32 Programmable I/O Lines
- Two 16-Bit Timer/Counters
- Six Interrupt Sources
- Programmable Serial Channel
- Low Power Idle and Power Down Modes
Reviews
There are no reviews yet.