Available on TI-99/4A computers. On the right side
| Pin | Name | Dir | Description |
|---|
| 1 | VCC | - | +5 Volts power supply |
| 2 | SBE | OUT | Low if addr in >9000-94xx (sound port) |
| 3 | RESET* | OUT | System reset (active low) |
| 4 | EXTINT* | IN | External interrupt (active low) |
| 5 | A5 | OUT | Address bus, bit 5 |
| 6 | A10 | OUT | - |
| 7 | A4 | OUT | - |
| 8 | A11 | OUT | - |
| 9 | DBIN | OUT | Active high = read memory |
| 10 | A3 | OUT | - |
| 11 | A12 | OUT | - |
| 12 | READY | IN | Active high = memory is ready |
| 13 | LOAD* | IN | Unmaskable interrupt (=> BLWP @>FFFC) |
| 14 | A8 | OUT | - |
| 15 | A13 | OUT | - |
| 16 | A14 | OUT | - |
| 17 | A7 | OUT | - |
| 18 | A9 | OUT | - |
| 19 | A15 | OUT | Address bus, lsb. Also CRU output bit. |
| 20 | A2 | OUT | - |
| 21 | GND | - | Ground |
| 22 | CRUCLK* | OUT | Inversion of TMS9900 CRUCLOCK pin |
| 23 | GND | - | Ground |
| 24 | PHI3* | OUT | Inversion of phase 3 clock |
| 25 | GND | - | Ground |
| 26 | WE* | OUT | Write Enable (derived from TMS9900 WE* pin) |
| 27 | GND | - | Ground |
| 28 | MBE* | OUT | Active low if addr in >4000-5FFF (card ROMs) |
| 29 | A6 | OUT | - |
| 30 | A1 | OUT | - |
| 31 | A0 | OUT | Address bus, bit 0 (most significant) |
| 32 | MEMEN* | OUT | Memory access enable (active low) |
| 33 | CRUIN | IN | CRU input bit to TMS9900 |
| 34 | D7 | IN/OUT | Data bus, bit 7 (least significant) |
| 35 | D4 | IN/OUT | - |
| 36 | D6 | IN/OUT | - |
| 37 | D0 | IN/OUT | Data bus, bit 0 (most significant) |
| 38 | D5 | IN/OUT | - |
| 39 | D2 | IN/OUT | - |
| 40 | D1 | IN/OUT | - |
| 41 | IAQ | IN | Interrupt acknowledged by TMS9900 |
| 42 | D3 | IN/OUT | - |
| 43 | VDD | - | -5 Volts power supply |
| 44 | AUDIOIN | IN | To sound generator AUDIO IN pin |