STA

Store Accumulator to Memory

Tags:

6502 instruction

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

Syntax	Opcode	Available on:			# of	# of	Addressing Mode
Syntax	(hex)	6502	65C02	65816	bytes	cycles	Addressing Mode
STA addr	8D	x	x	x	3	4¹	Absolute
STA long	8F			x	4	5¹	Absolute Long
STA dp	85	x	x	x	2	3^{1, 2}	Direct Page
STA (dp)	92		x	x	2	5^{1, 2}	Direct Page Indirect
STA [dp]	87			x	2	6^{1, 2}	Direct Page Indirect Long
STA addr,X	9D	x	x	x	3	4¹	Absolute Indexed X
STA long,X	9F			x	4	5¹	Absolute Long Indexed X
STA addr,Y	99	x	x	x	3	4¹	Absolute Indexed Y
STA dp,X	95	x	x	x	2	4^{1, 2}	Direct Page Indexed X
STA (dp,X)	81	x	x	x	2	6^{1, 2}	Direct Page Indexed Indirect X
STA (dp),Y	91	x	x	x	2	5^{1, 2}	Direct Page Indirect Indexed Y
STA [dp],Y	97			x	2	6^{1, 2}	Direct Page Indirect Long Indexed Y
STA sr,S	83			x	2	4¹	Stack Relative
STA (sr,S),Y	93			x	2	7¹	Stack Relative Indirect Indexed Y

Notes:

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

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