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Z80 running CP\M

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FreeThinker:

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Thinking back to my RMIT days, I probably should have submitted the Z-80 cross assembler I wrote that ran on a 6809!
It never really crossed my mind as the task was to build a piece of Z-80 hardware.  ::)

As for the undoc'd instructions, they actually make perfect sense when you look at the binary patterns of the opcodes, and the "holes" in the instruction tables.
Yes, this was all part of understanding the real opcodes to build the cross assembler.


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Yes the undocumented opcodes do make perfect sense when you look at the binary pattern ,but unfortunately they do not perform as expected (corruption of the flag reg I seem to remember) which is why they were left out of the official listing, I think the standard workaround was to push and pop the flag reg before and after there use if the flag status was needed to be preserved.

not_Dave:
Ben Ryves got something going on with Z80. you should definitely check it out.

http://benryves.com/journal

asgard:
If you are feeling up to it, you can implement a bank-switched page in the memory space which can be used as a
fast external memory outside the 64K to contain the BDOS image when you are using CP/M.  That way the infamous
BDOS load error can be avoided during warm boots.  It also chews up the FCB table a lot less, if you are using flash
memory for the filesystem.

J.R.

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