LDA

Load Accumulator from Memory
Tags:

Load the accumulator with data from memory.

On all processors, the data loaded from memory is 8-bit. However, for 16-bit processors with the m flag is clear then the data added is 16-bit with the low-order 8-bits at the effective address and the high-order 8-bits at the effective address plus one.

Flags Affected
Flags
n-----z-
nSet if most-significant bit of result is set
zSet if result is zero
Instructions
SyntaxOpcode Available on: # of # of Addressing Mode
(hex) 6502 65C02 65816 bytes cycles
LDA #constA9 x x x 21 22 Immediate
LDA addrAD x x x 3 42 Absolute
LDA longAF x 4 52 Absolute Long
LDA dpA5 x x x 2 32, 3 Direct Page
LDA (dp)B2 x x 2 52, 3 Direct Page Indirect
LDA [dp]A7 x 2 62, 3 Direct Page Indirect Long
LDA addr,XBD x x x 3 42, 4 Absolute Indexed X
LDA long,XBF x 4 52 Absolute Long Indexed X
LDA addr,YB9 x x x 3 42, 4 Absolute Indexed Y
LDA dp,XB5 x x x 2 42, 3 Direct Page Indexed X
LDA (dp,X)A1 x x x 2 62, 3 Direct Page Indexed Indirect X
LDA (dp),YB1 x x x 2 52, 3, 4 Direct Page Indirect Indexed Y
LDA [dp],YB7 x 2 62, 3 Direct Page Indirect Long Indexed Y
LDA sr,SA3 x 2 42 Stack Relative
LDA (sr,S),YB3 x 2 72 Stack Relative Indirect Indexed Y

Notes:

  1. 65816: Add 1 byte if m=0 (16-bit memory/accumulator)
  2. 65816: Add 1 cycle if m=0 (16-bit memory/accumulator)
  3. 65816: Add 1 cycle if low byte of Direct Page register is not 0
  4. Add 1 cycle if adding index crosses a page boundary
Last modified November 5, 2021: Add instruction categories (6b74ff9)