Low Risk Instruction Set (name pending) - if a CPU architecture was made by an insane person
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README.md

LRIS CPU/ASM specification (wip)

shamelessly ripped off very inspired by 6502 because it's the only thing i kinda know

Registers

Register Purpose Size
ACC Stores the result of any calculation opcodes (if in ACC mode) 1 byte
RAX General purpose register 1 byte
RAY General purpose register 1 byte

Memory

  • Up to 64kib of RAM
  • Up to 64kib of Program ROM

Addressing Modes

Absolute

Directly reads from a 2 byte memory address with instruction.

LDX $0A2F

Note: 1 byte addresses should be padded by the assembler.

Literal

Uses a literal byte, in place of reading from a memory address.

LDX #0A2F

Note: 1 byte addresses should be padded by the assembler.

Opcodes

NOTE: these do not specify a higher level assembly langauge, only the opcodes interpreted by the CPU itself (ie there cannot be 3 increments for the different registers that all use INC)

NOP- No Operation

seriously?

Addressing Action Opcode Size
N/A NOP $00 1 byte

INC - Increment

what do you think it does

Addressing Action Opcode Size
Absolute Increments the value at specified memory address $01 3 bytes
Accumulator Increments the accumulator $02 1 byte
RX Increments the RAX register $03 1 byte
RY Increments the RAY register $04 1 byte

DNC - Decrement

what do you think it does (pt. 2)

Addressing Action Opcode Size
Absolute Decrements the value at specified memory address $05 3 bytes
Accumulator Decrements the accumulator $06 1 byte
RX Decrements the RAX register $07 1 byte
RY Decrements the RAY register $08 1 byte

JIE - Jump If Equal

jumps if something is equal to other something

Addressing Action Opcode Size
Absolute/Literal Sets PRC to value if memory address is equal to other memory address $10 7 bytes
Register/Literal Sets PRC to value if RAX and RAY are equal $11 1 byte

JMP - Jump

jumps unconditionally

Addressing Action Opcode Size
Literal Sets PRC to a literal value $1A 3 bytes
Absolute Sets PRC to the value of a byte in memory $1B 3 bytes
Example:
;OP PRC    ADDR   ADDR
JIE 0x00A2 0x0013 0x0014

LDX - Load [RA]X

loads a value into RAX

Addressing Action Opcode Size
Absolute Loads the value of another byte of memory into RAX $20 3 bytes
Literal Loads a literal byte into RAX $21 2 bytes

LDY - Load [RA]Y

loads a value into RAY

Addressing Action Opcode Size
Absolute Loads the value of another byte of memory into RAY $22 3 bytes
Literal Loads a literal byte into RAY $23 2 bytes

LDA - Load A(ccumulator)

loads a value into the accumulator

Addressing Action Opcode Size
Absolute Loads the value of another byte of memory into ACC $24 3 bytes
Literal Loads a literal byte into ACC $25 2 bytes

LOD - Load Address

loads a value into an address

Addressing Action Opcode Size
Absolute Loads the value of another byte of memory into the memory address $26 5 bytes
Literal Loads a literal byte into the memory address $27 4 bytes

STX - Store [RA]X

stores RAX into a memory address

Addressing Action Opcode Size
Absolute Loads the value of RAX into a byte of memory $2A 3 bytes

STY - Store [RA]Y

stores RAY into a memory address

Addressing Action Opcode Size
Absolute Loads the value of RAY into a byte of memory $2B 3 bytes

STA - Store A(ccumulator)

stores the accumulator into a memory address

Addressing Action Opcode Size
Absolute Loads the value of ACC into a byte of memory $2C 3 bytes

ADD - Adds Two Values

adds two values of various source into a register or memory address

Addressing Action Opcode Size
RAX Adds RAX to the value in ACC, and stores it into ACC $40 1 byte
RAY Adds RAY to the value in ACC, and stores it into ACC $41 1 byte
Absolute/Absolute Adds the values of two memory addresses, and stores it into ACC $42 5 bytes
Absolute/ACC Adds the value of a memory address into the value in ACC, and stores it into ACC $43 3 bytes

SUB - Subtracts Two Values

subtracts two values of various source into a register or memory address

Addressing Action Opcode Size
RAX Subtracts RAX from the value in ACC, and stores it into ACC $45 1 byte
RAY Subtracts RAY from the value in ACC, and stores it into ACC $46 1 byte
Absolute/Absolute Subtracts the first address' value by the second address' value, and stores it into ACC $47 5 bytes
Absolute/ACC Subtracts the value of a memory address from the value in ACC, and stores it into ACC $48 3 bytes

NAD - NAND

if you don't know what a NAND is why are you looking at opcode documentation

Addressing Action Opcode Size
Register Performs a bitwise NAND on RAX and RAY and stores it into ACC $50 1 byte

HLT - Halt Operation

entirely stops execution and attempts to shutdown on hardware

Addressing Action Opcode Size
N/A $FC

DBG - Debug

(in emulators) print a view of memory
(in hardware or an optimizing assembler) NOP

Addressing Action Opcode Size
N/A $FF