TI-99/4A Side Port

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

Pinout

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

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

Note: Direction is computer relative device.

Note: * = active low.

Caution: Bit 0 being MSB is strange.

Contributions

• Joakim Ögren