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Old 12th Feb 2023, 5:56 pm   #181
ortek_service
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Default Re: Yet another MK14 tape interface (ESP32).

Quote:
Originally Posted by Mark1960 View Post
FF9-FFF are used to store users pointers and registers before and after calling users code. They are addressed using PC relative addressing from the low area of prom code to avoid using pointers as that would corrupt the user codes pointers. It seems the cassette loader was reusing the address for P1.
Thanks for info on what these are used for. So does that mean 0FF9-0FFF should never really have been used by user programs, if needing to return to the monitor? (And SCIOS v1 also used these?)

It might be useful to have an enhanced Memory-map diagram of:
http://81.174.146.201/acorn/Acorn%20...mory%20Map.pdf - that includes the parts reserved by the OS etc (like IIRC Siclair had in the original Spectrum manual)
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