Changes between Version 4 and Version 5 of vtech/cqfd-scientus


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Timestamp:
Aug 11, 2021, 6:05:07 PM (3 years ago)
Author:
pulkomandy
Comment:

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  • vtech/cqfd-scientus

    v4 v5  
    5050
    5151Page at 4000 is used to map 16K segments of the ROM. Each segment begins with a jumptable in the form of several JMP instructions.
     52Page at 8000 can also be used to map segments of the ROM.
     53
     54Some code also checks for writable areas when mapping things. So it appears it's possible to put RAM there too.
     55
     56I'm not sure if $2B and $2C are both used to control the mapping of the whole C000-FFFF area, and how they work together. I expect I will learn more about it as I study the code that is supposed to run from 4000 and 8000, as the main code seems to make almost no use of this higher area directly.
    5257
    5358The section at 2000 onwards is always visible by the CPU and a large part of it is code that selects a bank and then jump to a specific routine inside it. It also contains the subroutines mentionned above (stack management, ...) and some other code (uppercase/lowercase ASCII detection).