STA

Store Accumulator to Memory

Stores the accumulator into memory.

On all processors, the data written to memory is 8-bit. However, for 16-bit processors with the m flag is clear then the data written 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
None.
Instructions
SyntaxOpcode Available on: # of # of Addressing Mode
(hex) 6502 65C02 65816 bytes cycles
STA addr8D x x x 3 41 Absolute
STA long8F x 4 51 Absolute Long
STA dp85 x x x 2 31, 2 Direct Page
STA (dp)92 x x 2 51, 2 Direct Page Indirect
STA [dp]87 x 2 61, 2 Direct Page Indirect Long
STA addr,X9D x x x 3 41 Absolute Indexed X
STA long,X9F x 4 51 Absolute Long Indexed X
STA addr,Y99 x x x 3 41 Absolute Indexed Y
STA dp,X95 x x x 2 41, 2 Direct Page Indexed X
STA (dp,X)81 x x x 2 61, 2 Direct Page Indexed Indirect X
STA (dp),Y91 x x x 2 51, 2 Direct Page Indirect Indexed Y
STA [dp],Y97 x 2 61, 2 Direct Page Indirect Long Indexed Y
STA sr,S83 x 2 41 Stack Relative
STA (sr,S),Y93 x 2 71 Stack Relative Indirect Indexed Y

Notes:

  1. 65816: Add 1 cycle if m=0 (16-bit memory/accumulator)
  2. 65816: Add 1 cycle if low byte of Direct Page register is not 0

Last modified November 5, 2021: Add instruction categories (6b74ff9)