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TI-99/4A Card Slot(Inside PE Box)

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       59       Left       1 Front ===================== Rear       60       Right      2
PinNameDirDescription
1+5V 3-T regulator voltage supply (about +8V)
2-Dito
3GND-Ground
4READYA-System ready (10K pull-up to +5V)
5GND-Ground
6RESET*OUTSystem reset (active low)
7GND-Ground
8SCLKncSystem clock (not connected)
9LCP*ncCPU indicator 1=TI99 0=2nd generation (not connected)
10AUDIOINInput audio (=AUDIOIN)
11RDBENA*INActive low: enable flex cable data bus drivers (1K pull-up)
12PCBENHPCB enable for burn-in (always High)
13HOLD*HActive low CPU hold request (always High)
14IAQHAncIAQ [or] HOLDA (logical or)
15SENILA*HInterrupt level A sense enable (always High)
16SENILB*HInterrupt level B sense enable (always High)
17INTA*INActive low interrupt level A (=EXTINT*)
18LOAD*ncUnmaskable interrupt (not connected)
19D7IN/OUTData bus, bit 7 (least significant)
20GND-Ground
21D5IN/OUT
22D6IN/OUT
23D3IN/OUT
24D4IN/OUT
25D1IN/OUT
26D2IN/OUT
27GND-Ground
28D0IN/OUTData bus, bit 0 (most significant)
29A14OUT
30A15OUTAddress bus, lsb. Also CRU output bit.
31A12OUT
32A13OUT
33A10OUT
34A11OUT
35A8OUT
36A9OUT
37A6OUT
38A7OUT
39A4OUT
40A5OUT
41A2OUT
42A3OUT
43A0OUTAddress but, bit 0 (most significant)
44A1OUT
45AMBHExtra address bit. Always High.
46AMAHExtra address bit. Always High.
47GND-Ground
48AMCHExtra address bit. Always High.
49GND-Ground
50CLKOUT*OUTInversion of phase 3 clock (=PHI3*)
51CRUCLK*OUTInversion of TMS9900 CRUCLOCK pin
52DBINOUTActive high = read memory
53GND-Ground
54WE*OUTWrite Enable (derived from TMS9900 WE* pin)
55CRUININCRU input bit to TMS9900
56MEMEN*OUTMemory access enable (active low)
57-12 Volts 3-T regulator supply voltage (about -16V)
58Dito
59+12 Volts 3-T regulator supply voltage (about +16V)
60Dito

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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