169 (NORD-1 card)
169 Cambridge control, is a card that is used in the NORD-1 CPU.
It is a controller for interfacing the EXPANDARAM-18 core memory.
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The card is made in the standard NORD-1 card format.
|CPU model||Crate position|
The logic diagram is documented in drawing 2A69.
Switches and indicators
There are no switches or indicators on this board, but there is a strap field on the front. The four top positions are grounded and the four inputs have pullups.
Counting from the top :
- MT4 Goes to the edge connector 45 (MCIR0) but is also used internally on the card. This signal is also controlled by the MC0 signal from the edge connector 49.
- MT3 (Test I/O) : Goes straight to the edge connector 55 (MT30)
- MT2 : Goes straight to the edge connector 54 (MT20)
- MT1 (Repeated single) : Goes straight to the edge connector 53 (MT10)
Preliminary : The function seems to be to translate and ensure the timing of the control signals are correct. To do that it uses four JK-flip-flops (74107) and two one shots (74121) along with logical gates.
The card has a free running oscillator at about 2.5 MHz consisting of four inverters (3C) and RC circuits.
This list contains the logic circuits used, passive components are not listed.
- 2 x 7400 quad 2-input NAND gate
- 1 x 7401 quad 2-input NAND gate with open collector outputs
- 2 x 7402 quad 2-input NOR gate
- 5 x 7404 hex inverter
- 3 x 7410 triple 3-input NAND gate
- 2 x 7420 dual 4-input NAND gate
- 5 x 7440 dual 4-input NAND buffer
- 1 x 7450 dual 2-wide 2-input AND-OR-invert gate (one gate expandable)
- 2 x 74107 dual J-K flip-flop with clear
- 2 x 74121 monostable multivibrator
- HARDWARE MANUAL NORD 1
- Hardware in NORD-1 Serial 47