Mem pmod

Overview

SanicCPU32 (defined hereafter as SC32) is a 32-bit little-endian RISC with an integer ALU, support for up to 23-bit memory (in the current implementation), and 32 general purpose registers.

Instruction encoding

• Format 1 (Reg-reg arithmetic, indirect load/store):

  • AAAAACCCCCEEEEE

• Format 2 (Immediate arithmetic, direct load/store):

  • AAAAABBBDDDDDDDDDDDDDDDDDDDDDDDD

• Format 3 (Call):

  • AAAAADDDDDDDDDDDDDDDDDDDDDDDD

• Format 4 (Call indirect, Shift Right, POP, NOT):

  • AAAAACCCCC

• Format 5 (Load immediate upper):

  • AAAAACCCCCFFFFFFFFFFFFFFFF

• Format 6 (SMOV):

  • AAAAACCCCCGGGGG

• Format 7 (Branch):

  • AAAAAHHHDDDDDDDDDDDDDDDDDDDDDDDD

• Format 8 (Branch indirect):

  • AAAAAHHHCCCCC

• Legend

  • A: Always Opcode
  • B: 3-bit register index
  • C: 5-bit register index if the specific instruction supports it
  • D: 24-bit immediate for specific instructions that take that.
  • E: 5-bit register index for 2nd operand
  • F: 16-bit immediate
  • G: 5-bit special register index
  • H: 3-bit Branch condition

Instructions

TODO

Calling convention

There isn't a specific stack pointer register.

The ABI, though, uses the following:

R0 - function return R1 - return memory address R2 - stack pointer R3 -