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

Source: [The Hardware Book]

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