# TI-99/4A Cartridge Port

Available on TI-99/4A computers. On the top

      2                    36
    +----------------------------------+
    | ================================ |
    +----------------------------------+
      1                    35

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

Contributor: Joakim Ögren

Source:
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May be copied and redistributed, partially or in whole, as appropriate.
Document last modified: 2000-07-09