Nascom News­let­ter

4. O 5 AA   Send AAH to port B.
5. Q 4   This should return 55H.
6. Q 5   This should return AAH.

If a Graphics expansion board is fitted, care must be taken to ensure that the added IC does not short on the underside of the expansion board as it is mounted directly beneath.

The signal arriving from the F.D.C. card is a decode for ports 0 through to F but as there is no decoding involving a3 it means that there is only true decoding for ports 0 to 7.

Although not tested, it can be assumed that this modification will also work when used with a P.I.O. board, allowing the original P.I.O. to be used as well as the newly added ones.

Should you for any reason no longer require this modification, all that is needed is a new 74LS00 plugging in and the I/O link replacing.