| Pin | Name | Direction | Description |
|---|
| 1 | VCC | --- | +5 Volts power supply |
| 2 | SBE | Output | Low if addr in >9000-94xx (sound port) |
| 3 | RESET* | Output | System reset (active low) |
| 4 | EXTINT* | Input | External interrupt (active low) |
| 5 | A5 | Output | Address bus, bit 5 |
| 6 | A10 | Output | - |
| 7 | A4 | Output | - |
| 8 | A11 | Output | - |
| 9 | DBIN | Output | Active high = read memory |
| 10 | A3 | Output | - |
| 11 | A12 | Output | - |
| 12 | READY | Input | Active high = memory is ready |
| 13 | LOAD* | Input | Unmaskable interrupt (=> BLWP @>FFFC) |
| 14 | A8 | Output | - |
| 15 | A13 | Output | - |
| 16 | A14 | Output | - |
| 17 | A7 | Output | - |
| 18 | A9 | Output | - |
| 19 | A15 | Output | Address bus, lsb. Also CRU output bit. |
| 20 | A2 | Output | - |
| 21 | GND | --- | Ground |
| 22 | CRUCLK* | Output | Inversion of TMS9900 CRUCLOCK pin |
| 23 | GND | --- | Ground |
| 24 | PHI3* | Output | Inversion of phase 3 clock |
| 25 | GND | --- | Ground |
| 26 | WE* | Output | Write Enable (derived from TMS9900 WE* pin) |
| 27 | GND | --- | Ground |
| 28 | MBE* | Output | Active low if addr in >4000-5FFF (card ROMs) |
| 29 | A6 | Output | - |
| 30 | A1 | Output | - |
| 31 | A0 | Output | Address bus, bit 0 (most significant) |
| 32 | MEMEN* | Output | Memory access enable (active low) |
| 33 | CRUIN | Input | CRU input bit to TMS9900 |
| 34 | D7 | Input | Data bus, bit 7 (least significant) |
| 35 | D4 | Input | - |
| 36 | D6 | Input | - |
| 37 | D0 | Input | Data bus, bit 0 (most significant) |
| 38 | D5 | Input | - |
| 39 | D2 | Input | - |
| 40 | D1 | Input | - |
| 41 | IAQ | Input | Interrupt acknowledged by TMS9900 |
| 42 | D3 | Input | - |
| 43 | VDD | --- | -5 Volts power supply |
| 44 | AUDIOIN | Input | To sound generator AUDIO IN pin |
