This is a fun project similar to z80fun: An MCS-51 (80C31) microcontroller supported by an AVR, that provides ROM, extended RAM and clock.
- The hardware is wired on a breadboard.
- It's based on a Pro Micro 3.3V/8MHz board.
- The 80C31 runs at 1/26 the speed of the AVR which is about 308kHz.
- There is some MCS-51 example code written in C.
- It can communicate via the 80C31 integrated UART (at 1600 baud).
- And it can compute primes (just press p).
- RAM is essentially limited by the AVR's internal SRAM (2.5kB).
- ROM size is limited by the number of address lines (4kB).
| 8031 | AVR | Pro Micro Pin |
|---|---|---|
| P0.0/AD0 | PB1 | 15 |
| P0.1/AD1 | PB2 | 16 |
| P0.2/AD2 | PB3 | 14 |
| P0.3/AD3 | PB4 | 8 |
| P0.4/AD4 | PF4 | A3 |
| P0.5/AD5 | PF5 | A2 |
| P0.6/AD6 | PF6 | A1 |
| P0.7/AD7 | PF7 | A0 |
| P2.0/A8 | PD2 | RXI |
| P2.1/A9 | PD3 | TXO |
| P2.2/A10 | PD4 | 4 |
| P2.3/A11 | PD7 | 6 |
| ALE | PE6 | 7 |
| /PSEN | PD0 | 3 |
| /RD | PD1 | 2 |
| /WR | PC6 | 5 |
| RST | PB5 | 9 |
| XTAL1 | PB6 | 10 |
| 8031 | peripherals |
|---|---|
| P3.0/RxD | Serial-to-USB converter (3.3V) |
| P3.1/TxD | Serial-to-USB converter (3.3V) |
| P3.4 | LED and resistor in series connected to VCC |
| P3.5 | LED and resistor in series connected to VCC |