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TI-99 OS Development

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#26 Gip-Gip OFFLINE  


    Chopper Commander

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  • 152 posts
  • Location:Georgia, US

Posted Wed May 24, 2017 6:43 PM

I think I have a good layout for the PAD ram so-far. I'll most-likely be programming in assembler (not what I was hoping for) due to the lack of room for a stack. 


>8000->800F: Registers
>8010->801E: Memory device map
>801F->802D: Process callpoints
>802E->807F: Memory map
Memory-device map entry-layout
Word 1 - Start Address
Word 2 - End Address
Word 3 - Read/Write Call
Memory map entry-layout
Word 1 - Start Addr
Word 2 - End Addr
Process callpoint entry-layout
Word 1 - Program Counter (See notes)
Word 2 - Accumulator
Word 3 - Flags
  • The program counter is not immediate, in that it is only used when the task is first accessed, and changes to it will not be recognized until the task gives up control
  • You can only run up to 5 programs at a time, have 41 memory allocations, and 5 memory devices, due to the limitations of the PAD ram.
  • Memory allocations have a fix-length (4-byte) string preceding their start-address. This is their ID

Edited by Gip-Gip, Wed May 24, 2017 7:59 PM.

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