INMC 80 News


February–April 1981, Issue 3

Page 15 of 55

The link LK1 must be left in the internal position (to select internal decoding IOEXT must now be connected to IORQ. Now with IOEXT lo A2 selects between the internal ports, while IOEXT hi disables the on board ports as it should.

To make this modification disconect pin 2 of IC45 and pin 5 of IC46 by cutting the tracks on the component side, then join these two points together and to the IOEXT line at LK1, on the solder side. You can then build your IO board with the following decoding:

Yours faithfully,

D. Ritchie.

Circuit Diagram for modifying RAM A

See ‘32K – 48K Expansion’ article.

Page 15 of 55