Data model

Types

• int - 16 bits
• char - 8 bits
• pointer - 16 bits

Registers

• Callee saved: R0 | A, R2, R4, R5, R8, R9 | IH, R10 | IL.
• Caller saved: R1, R3, R6, R7, R11 | FPH, R12 | FPL.
• System: R13 | SPH, R14 | SPL, R15 | F.

Calling rules:

• Function arguments: first three in R1, R2, R3; the rest on the stack.
• Return value: always in R0 (A).
• Frame pointer: 16-bit value in FPH:FPL.
• Stack pointer: 16-bit value in SPH:SPL; stack starts at 0xBFFF and grows downward.
• Index register: IH:IL is a free 16-bit index pair for addressing.