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TI-99/4A Side Port

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

  2                    44
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  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: ?

Copyright © The Hardware Book Team 1996-2004.
May be copied and redistributed, partially or in whole, as appropriate.
Document last modified: 2002-01-10