Instruction Format

RIX8 uses a fixed 16-bit instruction width. Every instruction is fetched from external flash.

Bit layout

Every instruction follows this format:

Field	Bits	Width	Description
opcode	15–12	4	Operation selector (16 possible opcodes)
rd	11–9	3	Destination register (R0–R7)
rs1	8–6	3	First source register (R0–R7)
rs2 / imm6	5–0	6	Second source register or 6-bit immediate

The decoding of last 6-bit depends on the specific instruction. For register-register operation, it selects rs2. For immediate operations, it carries a 6-bit constant.