80-Bus News

exists by what it is in the correct place, and what isn’t. If you can’t even find the EPROM, then the fault may lie in the /CS decoding, or the enable to the output buffer. It is at times like these that a ’scope (or logic probe) is useful, especially when used in conjunction with a complex test program like:

A tight loop like this allows you to synchronise a ’scope easily, and to follow various signals through the circuit.

If everthing checks out to this point, but problems still exist in executing programs in the EPROMs, then it looks like its a case of switching on wait-states. (Or else revising the modifications to generate an earlier /CS signal.)

Climax Problems (No it’s not that type of Agony column)

It has come to my notice that somebody has problems in trying to use the Climax card in a Gemini Network system. After initial suspicions of the software, it was finally realised that some Network systems had been shipped fitted with a particular model of power-supply which did not provide a -5v supply – a fact that didn’t matter with the supplied boards (GM813 CPU + RAM, IVC, etc). The Climax, however, uses 4116 RAMS (which require a −5V supply), and so when this oversight was rectified.... This struck a chord with me, because I can remember doing something similar several years ago. I hadn’t bothered to wire the -12v supply through the backplane because I didn’t use it, and then some months later came to connect a serial printer to the RS232 interface....

[1] Zienkiewicz A.O. “Modification to ‘TYPE A’ RAM board”, INMC80-5 Oct-Dec 1981