Thread: Mk14 vdu
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Old 10th Nov 2020, 4:09 pm   #866
SiriusHardware
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Default Re: Mk14 vdu

Quote:
Originally Posted by Mark1960 View Post
I was thinking the address decoding would be duplicated off board rather than share the 8154
Well, let's say you decide to map the extra hardware at 0840, above the range of the registers in the I/O portion of the 8154 but below the block occupied by the 8154 RAM (0880-08FF)

Even though there are no registers in the 8154 residing at that address, the _CE for the 8154 probably selects that IC anywhere within the 0800-087F block so it may clash with anything else you try to map into there. There may even be images of the 8154 I/O registers filling up the 0800-087F block.

That's why I think you would have to either intercept and further decode the 8154 chip select on the MK14 board, or, move the 8154 offboard and do the address decoding for it and the extra hardware there.
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