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Mark1960 · 12th Feb 2023, 5:40 pm

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.

12th Feb 2023, 5:40 pm	#180
Mark1960 Octode Join Date: Mar 2020 Location: Kitchener, Ontario, Canada Posts: 1,298	Re: Yet another MK14 tape interface (ESP32). 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.