| Pin | Name | Direction | Description |
|---|
| 1 | RESET | Input | Resets the system (active high) |
| 2 | GND | --- | Signal groud |
| 3 | D7 | Input | Data bus, bit 7 (least significant) |
| 4 | CRUCLK* | Output | Inversion of TMS9900 CRUCLOCK pin |
| 5 | D6 | Input | |
| 6 | CRUIN | Input | CRU input to TMS9900 |
| 7 | D5 | Input | |
| 8 | A15 | Output | Address bus, bit 15 / also CRU output bit |
| 9 | D4 | Input | |
| 10 | A13 | Output | |
| 11 | D3 | Input | |
| 12 | A12 | Output | |
| 13 | D2 | Input | |
| 14 | A11 | Output | |
| 15 | D1 | Input | |
| 16 | A10 | Output | |
| 17 | D0 | Input | Data bus, bit 0 (most significant) |
| 18 | A9 | Output | |
| 19 | VCC | --- | +5 Volts power supply |
| 20 | A8 | Output | |
| 21 | GS* | Output | Grom select. Active low is addr in >9800-9FFF |
| 22 | A7 | Output | |
| 23 | A14 | Output | Address bus, bit 14. Select mode: low=data / high=addr |
| 24 | A3 | Output | |
| 25 | DBIN | Output | Active high = read memory |
| 26 | A6 | Output | |
| 27 | GRC | Output | GROM clock: color burst of VDP 9918A |
| 28 | A5 | Output | |
| 29 | VDD | --- | -5 Volts power supply |
| 30 | A4 | Output | |
| 31 | GR | Input | Active high = GROM ready |
| 32 | WE* | Output | Active low = write enable (derived from TMS9900 WE*) |
| 33 | VSS | --- | |
| 34 | ROMG* | Output | Active low if addr in >6000-7FFF |
| 35 | GND | --- | Ground |
| 36 | GND | --- | Ground |
