This chip handles keyboard and tape I/O.
| <---> | Pa3 | 1 |
U
8255 |
40 | PA4 | <---> |
| <---> | PA2 | 2 | 39 | PA5 | <---> | |
| <---> | PA1 | 3 | 38 | PA6 | <---> | |
| <---> | PA0 | 4 | 37 | PA7 | <---> | |
| !RD | 5 | 36 | Vcc | |||
| !CS | 6 | 35 | Reset | |||
| Gnd | 7 | 34 | D0 | |||
| A1 | 8 | 33 | D1 | |||
| A0 | 9 | 32 | D2 | |||
| <---> | PC7 | 10 | 31 | D3 | ||
| <---> | PC6 | 11 | 30 | D4 | ||
| <---> | PC5 | 12 | 29 | D5 | ||
| <---> | PC4 | 13 | 28 | D6 | ||
| <---> | PC3 | 14 | 27 | D7 | ||
| <---> | PC2 | 15 | 26 | !WR | ||
| <---> | PC1 | 16 | 25 | PB7 | <---> | |
| <---> | PC0 | 17 | 24 | PB6 | <---> | |
| <---> | PB0 | 18 | 23 | PB5 | <---> | |
| <---> | PB1 | 19 | 22 | PB4 | <---> | |
| <---> | PB2 | 20 | 21 | PB3 | <---> |
| Offset | Register |
00 |
Data register |
01 |
Index register |
Address = Base + Offset |