LDA (LoaD Accumulator)¶

A = [operand]

LDA (LoaD Accumulator) is an instruction that loads a value from memory into the accumulator register (A). The operand can be either an immediate value, a memory location specified by its address, or a memory location specified by an indexed indirect or indirect indexed address.

The result is stored in the accumulator, and the Zero and Negative flags are set based on the result.

Addressing Modes¶

Mode	Syntax	Bytes	Cycles
Immediate	LDA #const	`A9 nn`	2
ZeroPage	LDA zp	`A5 nn`	3
ZeroPage+X	LDA zp,x	`B5 nn`	4
Absolute	LDA addr	`AD ll hh`	4
Absolute+X	LDA addr,x	`BD ll hh`	4-5
Absolute+Y	LDA addr,y	`B9 ll hh`	4-5
(Indirect+X)	LDA (zp,x)	`A1 nn`	6
(Indirect)+Y	LDA (zp),y	`B1 nn`	5-6

Flags Affected¶

N (Negative) – Set if the loaded value has the most significant bit set (i.e., is negative); otherwise, it is cleared.
Z (Zero) – Set if the loaded value is zero; otherwise, it is cleared.

Examples¶

Load a Constant into the Accumulator¶

    LDA #10    ; load A with constant 10

Load a Value from a Memory Location¶

    LDA $20    ; load A with the value at memory location $20

Load a Value from a Memory Location with an Offset¶

    LDX #2     ; load X with 2
    LDA $10,X  ; load A with the value at memory location $12 ($10 + X)