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TI-99/4A Card Slot

60 PIN UNKNOWN CONNECTOR on the computer

        59     Left     1
Front ===================== Rear
        60     Right    2

Pin	Name	Dir	Description
1	+8V		+5V 3-T regulator voltage supply (about +8V)
2	+8V		+5V 3-T regulator voltage supply (about +8V)
3	GND		Ground
4	READYA		System ready (10K pull-up to +5V)
5	GND		Ground
6	RESET*		System reset (active low)
7	GND		Ground
8	SCLK	nc	System clock (not connected)
9	LCP*	nc	CPU indicator 1=TI99 0=2nd generation (not connected)
10	AUDIO		Input audio (=AUDIOIN)
11	RDBENA*		Active low: enable flex cable data bus drivers (1K pull-up)
12	PCBEN	H	PCB enable for burn-in (always High)
13	HOLD*	H	Active low CPU hold request (always High)
14	IAQHA	nc	IAQ [or] HOLDA (logical or)
15	SENILA*	H	Interrupt level A sense enable (always High)
16	SENILB*	H	Interrupt level B sense enable (always High)
17	INTA*		Active low interrupt level A (=EXTINT*)
18	LOAD*	nc	Unmaskable interrupt (not connected)
19	D7		Data bit 7 (LSB)
20	GND		Ground
21	D5		Data bit 5
22	D6		Data bit 6
23	D3		Data bit 3
24	D4		Data bit 4
25	D1		Data bit 1
26	D2		Data bit 2
27	GND		Ground
28	D0		Data bit 0 (MSB)
29	A14		Address bit 14
30	A15		Address bit 15 (LSB). Also CRU output bit.
31	A12		Address bit 12
32	A13		Address bit 13
33	A10		Address bit 10
34	A11		Address bit 11
35	A8		Address bit 8
36	A9		Address bit 9
37	A6		Address bit 6
38	A7		Address bit 7
39	A4		Address bit 4
40	A5		Address bit 5
41	A2		Address bit 2
42	A3		Address bit 3
43	A0		Address bit 0 (MSB)
44	A1		Address bit 1
45	AMB	H	Extra address bit. Always High.
46	AMA	H	Extra address bit. Always High.
47	GND		Ground
48	AMC	H	Extra address bit. Always High.
49	GND		Ground
50	CLKOUT*		Inversion of phase 3 clock (=PHI3*)
51	CRUCLK*		Inversion of TMS9900 CRUCLOCK pin
52	DBIN		Active high = read memory
53	GND		Ground
54	WE*		Write Enable (derived from TMS9900 WE* pin)
55	CRUIN		CRU input bit to TMS9900
56	MEMEN*		Memory access enable (active low)
57	-12V		-12 Volts 3-T regulator supply voltage (about -16V)
58	-12V		-12 Volts 3-T regulator supply voltage (about -16V)
59	+12V		+12 Volts 3-T regulator supply voltage (about +16V)
60	+12V		+12 Volts 3-T regulator supply voltage (about +16V)

Direction is computer relative world.

Notes:

• Signals buffered by 74LS244 in connection card: A0-A15, DBIN, MEMEN*, WE*, CLRCLK*, RESET*, CLKOUT.
• Unbuffered signals: CRUIN, INTA*, AUDIOIN, READY
• Data bus is buffered by two 74LS245 (one at each end of the cable),driven by RDBENA (direction set by DBIN).
• All signals must be re-buffered on each card.
• Always High lines (AMA, AMB, AMC, SENILA*, SENILB*, PCBEN, HOLD*) are pulled up to +5 Volts by 47 Ohms resistors.

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