| PIN | DESC | FUNCTION |
|---|---|---|
| 1 | Vss | Ground. |
| 2-9 | PA0-PA7 | Peripheral I/O Port A. |
| 10-17 | PB0-PB7 | Peripheral I/O Port B. |
| 18,19 | CB1,CB2 | Peripheral B Control Lines. |
| 20 | Vcc | +5VDC. |
| 21 | IRQ | Interrupt Request. |
| 22 | R/W | Read/Write. |
| 23,24 | CS1,CS2 | Chip Select. |
| 25 | 02 | Phase 2 Internal Clock. |
| 26-33 | D0-D7 | Data Bus. |
| 34 | RES | Reset Input, Low Active. |
| 35-38 | RS0-RS3 | Register Select Inputs. |
| 39,40 | CA1,CA2 | Peripheral A Control Lines. |