# TI-99/4A Side Port

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

      2                    44
    +----------------------------------+
    | ================================ |
    +----------------------------------+
      1                    43

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

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