(Recovered from SMWiki, improvements are welcome.)
Revision as of 22:53, 9 November 2019
There are approximately 91 opcodes in ASM. They are divided into different categories.
These instructions load an 8-bit or a 16-bit value into one of the three registers.
|LDA||Load into accumulator from memory|
|LDX||Load into X from memory|
|LDY||Load into Y from memory|
These instructions, usually used with branch commands, compare one of the three registers with a value or memory. (They essentially subtract the value following the compare instruction from the value in the register, affecting the processor flags but not the register itself.)
|CMP||Compare accumulator with memory|
|CPY||Compare Y with memory|
|CPX||Compare X with memory|
These instructions store various values from a register into memory.
STA - Store Accumulator to Memory STX - Store X to Memory STY - Store Y to Memory STZ - Store Zero to Memory
These instructions branch depending on the processor flags' status, except BRA and BRL, which always branch regardless of the processor flags.
BCC - Branch if Carry Clear BCS - Branch if Carry Set BPL - Branch if Plus value BMI - Branch if Minus value BNE - Branch if not Equal/Branch if not zero BEQ - Branch if Equal/Branch if zero BVC - Branch if Overflow Clear BVS - Branch if Overflow Set BRL - Branch Always Long BRA - Branch Always
These instructions perform addition and subtraction with the registers and memory. (Note that there are no opcodes for multiplication and division; special registers must be used for those.)
ADC - Add with carry SBC - Subtract with Carry INC - Increment Accumulator or Memory INX - Increment X INY - Increment Y DEC - Decrement Accumulator or Memory DEX - Decrement X DEY - Decrement Y
Processor flag instructions
These instructions set or clear various processor flags of the SNES.
SEP - Set Processor Status Flag REP - Reset Processor Status Flag SEC - Set Carry Flag SED - Set Decimal Flag SEI - Set Interrupt Flag CLC - Clear Carry Flag CLD - Clear Decimal Flag CLI - Clear Interrupt Flag CLV - Clear Overflow Flag XCE - Exchange Carry and Emulation (swaps bits of emulation flag and carry flag, toggling emulation mode on/off)
These instructions push and pull various bytes on/from the stack, a special designated area of RAM that is located at $01FF-$010B in SMW.
PEA - Push Effective Address (Simply push a 16-bit absolute value on the stack) PEI - Push Effective Indirect Address PER - Push Program Counter Relative PHA - Push Accumulator PHB - Push Data Bank Register PHD - Push Direct Page Register PHK - Push Program Bank Register PHP - Push Processor Status Flags PHX - Push X PHY - Push Y PLA - Pull Accumulator PLB - Pull Data Bank Register PLD - Pull Direct Page Register PLP - Pull Processor Status Flags PLX - Pull X PLY - Pull Y
These operations affect the individual bits of A and/or memory.
AND - AND Accumulator with Memory ASL - Left Shift Accumulator or Memory BIT - Bit Test EOR - Exclusive OR Accumulator with Memory LSR - Shift Right Accumulator or Memory ORA - OR Accumulator with Memory ROL - Rotate Left Accumulator or Memory ROR - Rotate Right Accumulator or Memory TRB - Test and Reset Bit TSB - Test and Set Bit
These opcodes transfer values from register to register (or, in the case of MVN and MVP, from memory to memory).
TAX - Transfer Accumulator to X TAY - Transfer Accumulator to Y TCD - Transfer Accumulator to Direct Page TCS - Transfer Accumulator to Stack pointer TDC - Transfer Direct Page to Accumulator TSC - Transfer Stack Pointer to Accumulator TSX - Transfer Stack Pointer to X TXA - Transfer X to Accumulator TXS - Transfer X to Stack Pointer TXY - Transfer X to Y TYA - Transfer Y to Accumulator TYX - Transfer Y to X MVN - Block Move Negative MVP - Block Move Positive
Program flow instructions
These instructions jump into some other part of the ROM/RAM.
JML - Jump Long JMP - Jump JSL - Jump to Subroutine Long JSR - Jump to Subroutine RTI - Return from Interrupt RTL - Return from Subroutine Long RTS - Return from Subroutine
These are other misc. opcodes.
BRK - Software Break (Sets the B flag in emulation mode, interrupt in native) COP - Coprocessor Empowerment (interrupt) NOP - No operation (does absolutely nothing except waste a cycle of processing time) STP - Stop the Clock (freezes the SNES's processor) WAI - Wait for Interrupt XBA - Exchanges low and high byte of the A register