I am using EhBasic as an "OS" in my homemade 6502 computer. It works fine,but now I try to incorporate some own code, to run peripherals I used in my design.
Now I am trying to add support for 8242 AT keyboard controller. For that I need a "cell" in a memory, where I can store received scancodes. Can you pint me a fragment of a memory space I can use without interfering with normal operation of EhBasic? Is it possible to use some location in Zero Page or is it entirely reserved for EhBasic?

I do something very similar, as I suppose many other do too.

You can change ram_base to give you as much memory as you need. It is set at $0300 as a default. If you need 512 bytes of memory set it to $0500 and you can be sure that $0300-$04FF will be available to you.

I also put my routines in ROM between BASIC and the vector area, then use CALL and USR() to run them. If I need to set up more parameters than I can pass with USR() I will just poke them into RAM before calling the routine.

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Bill

You can safely use zero page locations $30 to $3F or $E2 to $EE. There are others also, but these are the ones I use the most.

Daryl

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Please visit my website -> https://sbc.rictor.org/

I don't use it anymore, but when I ported EhBASIC to my system, I found it only used Zero page locations < $90. That leaves lots for your own use. My own OS uses $90 through $FF so it fitted really well. I used the 65C02 port though but I doubt the original one would be any different.

Quick check now, it seems the version I have has a different way to define ZP variables - every variable is defines as the last one +1, so check the sources.

Cheers,

-Gordon

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Gordon Henderson.
See my Ruby 6502 and 65816 SBC projects here: https://projects.drogon.net/ruby/