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Instruction fetch should step program counter before fetch #1

@dallday

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@dallday

Hi Rob
Thanks for the Mk14 in python it has been most enlightening reading through your code.

There does seem a slight issue re emulating the SCMP chip. It does the add 1 to program counter before fetching the op-code. The current code fetches the op-code and then adds 1 to the program counter.
The Fix:-
switching around of the instructions in the "fetchIP" function.
removal of the subtract 1 from the Program Counter in the "indexed" function.

This also means that the initial start address is normally 1 less than address of the first op-code. This requires an amendment to all the demo programs.

I suspect this is a work in progress but it has been a great help in getting a MK14 emulator I can understand.

Regards
David

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