A 3-letter opcode for the 6502 processor. It is the most frequently used operation (a close second is probably the STA instruction). This opcode loads an 8-bit value in the main register (also called the Accumulator).

Back to the 6502 opcodes metanode

A 6502 instruction that loads a new value into the A register.
  • Function: N => A
  • Updates flags: S . . . . . Z .
  • Opcode numbers:
    (d,x) $A1
    dp    $A5
    imm   $A9
    abs   $AD
    a,x   $BD
    a,y   $B9
    (d),y $B1
    d,x   $B5
    

LDA imm is likely the most common 6502 instruction. If you've dumped a ROM image of an unknown CPU's program, and it contains lots of A9 bytes (especially if they're spaced five bytes apart), you may be looking at a 6502 binary.

Similar: LDX | LDY | STA
See also: 6502 instructions | 6502 addressing modes

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