Author Topic: PCW Expansion port MDIS pin 45  (Read 799 times)

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Offline JonB

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PCW Expansion port MDIS pin 45
« on: 14:34, 03 February 17 »
Hi


Does anyone know what the MDIS line does on the PCW expansion port? It's on pin 45:


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Also, the Z80 /REFSH, /HALT and /NMI lines do not appear to be present on the connector, is that right?

Offline Bryce

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Re: PCW Expansion port MDIS pin 45
« Reply #1 on: 14:36, 03 February 17 »
I would assume from the name that it disables the RAM, but a quick check of the schematics should tell you...

Bryce.

Offline JonB

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Re: PCW Expansion port MDIS pin 45
« Reply #2 on: 14:46, 03 February 17 »
It is connected to Pin 24 of the gate array, if that helps.


Do you have a good schematic of the CPU board? The service manual I have has only got the PCB layout.
« Last Edit: 14:48, 03 February 17 by JonB »

Offline Bryce

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Re: PCW Expansion port MDIS pin 45
« Reply #3 on: 14:57, 03 February 17 »
Yes, send me your e-mail address in a PM and I'll send you a very readable full Service Manual.

I've just checked and:

The CPU NMI has only a single connection from the CPU to the GA (Pin 47)
Halt and Refresh of the CPU aren't connected to anything at all.
MDIS goes directly to NMDIS (Pin 24) of the GA.

Bryce.