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