Volume 1, Number 3 – November 1981

Page 21 of 33

the switch to a high-impedance state. In the case of a 2708, only pin 20 can be used to select the chip.

The circuit can be used to switch between two sets of graphics held in a single 4K EPROM – a 2532. Only one 24-pin socket is required, and the output from the flip-flop is again connected to pin 18 of this socket – but in this case this is the top address line, switching between the two sets of 2K graphics data in the ROM. If the standard Nascom-2 graphics data is stored in the bottom 2K of the chip, pin 18 should be connected to pin 8 of the 74LS00.


1 wirewrap 24-pin socket
1 standard 24-pin socket
1 14-pin socket
1 10 kohm resistor

  FIG. 1  

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