25 Nov
2015
25 Nov
'15
11:38 a.m.
My reading of the Qbus spec is that P OK and DC OK are
active high. That diagram
They are, for a very logical reason. Remember you can wire-AND open-collector signals
-- that is link them together so that any driver can pull the line low and the line will
only be high if all driver transistors are cut off. Now if you have a large system
with multiple boxes and power supplies then any supply can pull P OK and DC OK low
if there is a problem. Only if all supplies are present and correct will the signals be
high.
-tony