Posted By
crock
on 2021-03-21
12:47:19
 |  Re: Plus/4 issues trying to solve with Diag264
Did you make the loop backs or yourself or did you buy them? If so, where from?
What is the value of the status byte when the cassette test fails?
The status of the ports as you show in your post are correct for when the dongles are attached, as the motor control pulls the sense line low. eg:
WRITE: FF => XXXXXXXX
READ: BB => X.XXX.XX
So, when you say "it doesn't change in any way", do you mean toggling the state of any of the bits when "writing" to the 6529 has no effect on the read value, or just for bit 2? If just for bit 2, this is expected. If you want to test bit 2, you will need to toggle bit 3 of the CPU port, like this:
WRITE: 00 => ----....
READ: D0 => XX.X....
Then, the 6529 port should show:
WRITE: FF => XXXXXXXX
READ: FF => XXXXXXXX
Then you should be able to toggle bit 2:
WRITE: FB => XXXXX.XX
READ: BB => X.XXX.XX
The "advanced port tests" are exactly as the name implies. It's difficult to use them meaningfully without understanding the plus/4 schematics and hardware architecture.
cheers, Rob
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