30997Re: [midatlanticretro] Re: CP/M CBIOS LST question
- May 26, 2013Thanks Herb. You are right in that the virtual devices like LST can be assigned to other physical devices, but not RDR or PUN (at least from what I read). It's not too big of a deal for me to enable the code and try it out. I guess it would be the same as if I had a switch box on a single serial port and selected what device I used.Fun!Rich
--- In email@example.com, Richard Cini <rich.cini@...> wrote:
> All --
> I'm rebuilding my CP/M 2.2 CBIOS and have a question. I have the PUN/RDR
> devices enabled and pointing to the second port on my console card, and I
> have the LST device disabled. I never use the PUN/RDR, so I was wondering if
> there was any reason that I shouldn't change the CBIOS to program the LST
> device to use the same port. I do have a second port on a second serial card
> free if I have to use it.
> Thanks for the advice.
If I recall, the "IOBYTE" function in later BIOS's permitted reassignment of devices among the LST, PUN, RDR and so on. Check the Digital Research manuals on this, or some of the various "how to write BIOS" CP/M books published. One can also look at BIOS listings in various floppy controller manuals and CP/M implementations, to see some interesting implementations. I think IOBYTE was a feature late to CP/M 2.0 and 2.2.
Otherwise, you can always poke I/O code into the BIOS memory area on-the-fly, and if you like it modify your BIOS on-disk. Just leave enough space on the disk image of BIOS, to poke it in, and separately of course from the conin/conout/constat code in the BIOS.
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