LDA

LDA (short for "LoaD Accumulator") is the mnemonic for a machine language instruction which retrieves a copy from the specified RAM or I/O address, and stores it in the accumulator. The content of the memory location is not affected by the operation.

Addressing modes

Opcode		Addressing mode	Assembler format	Length in bytes	Number of cycles
Dec	Hex
169	A9	Immediate	LDA #nn	2	2
173	AD	Absolute	LDA nnnn	3	4
189	BD	Absolute,X	LDA nnnn,X	3	4*
185	B9	Absolute,Y	LDA nnnn,Y	3	4*
165	A5	Zeropage	LDA nn	2	3
181	B5	Zeropage,X	LDA nn,X	2	4
161	A1	Indexed-indirect	LDA (nn,X)	2	6
177	B1	Indirect-indexed	LDA (nn),Y	2	5*

LDA supports eight different addressing modes, as shown in the table at right. In the assembler formats listed, nn represents a single-byte (8-bit) figure, and nnnn is a two-byte (16-bit) address.
With some addressing forms (marked with an asterisk, *, in the "Number of cycles" column) the execution time for LDA depends on the circumstances: In cases where the indexing requires the CPU to "reach across" a page boundary from the base address, the execution time is 1 cycle longer than listed here.

CPU flags

LDA affects 2 of the CPU's status flags:

• The negative status flag is set if the result is negative, i.e. has it's most significant bit set.
• The zero flag is set if the result is zero, or cleared if it is non-zero.