STA

Basic Info
Addressing Mode	Opcode	Length	Speed
absolute	8D	3 bytes	4 cycles*
absolute long	8F	4 bytes	5 cycles*
direct page	85	2 bytes	3 cycles*
direct page indirect	92	2 bytes	5 cycles*
direct page indirect long	87	2 bytes	6 cycles*
absolute indexed by X	9D	3 bytes	4 cycles*
absolute long indexed by X	9F	4 bytes	5 cycles*
absolute indexed by Y	99	3 bytes	4 cycles*
direct page indexed by X	95	2 bytes	4 cycles*
direct page indexed indirect by X	81	2 bytes	6 cycles*
direct page indirect indexed by Y	91	2 bytes	5 cycles*
direct page indirect long indexed by Y	97	2 bytes	6 cycles*
stack relative	83	2 bytes	4 cycles*
stack relative indirect indexed by Y	93	2 bytes	7 cycles*

Flags Affected
N	V	M	X	D	I	Z	C
.	.	.	.	.	.	.	.

STA (Store Accumulator) is a 65x instruction that stores the value of the accumulator. In all addressing modes, STA takes one additional cycle when the accumulator is 16 bits wide. In direct page addressing modes, STA takes another additional cycle if the low byte of the direct page register is nonzero.

See Also

• STX
• STY
• STZ

External Links

• Eyes & Lichty page on STA: https://archive.org/details/0893037893ProgrammingThe65816/page/n529
• Labiak page on STA: https://archive.org/details/Programming_the_65816/page/n194
• MCS6500 Manual page on STA: https://archive.org/details/mos_microcomputers_programming_manual/page/n20
• Carr page on STA: https://archive.org/details/6502UsersManual/page/n286
• Leventhal page on STA: https://archive.org/details/6502-assembly-language-programming/page/n145
• snes9x implementation of STA: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1219
• undisbeliever on STA: https://undisbeliever.net/snesdev/65816-opcodes.html#sta-store-accumulator-to-memory