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STA: Difference between revisions

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'''STA''' (Store Accumulator) is a 65x instruction that stores the value of the [[accumulator]].
'''STA''' (Store Accumulator) is a 65x instruction that stores the value of the [[accumulator]].  If the accumulator is 16 bits wide, its low byte is stored at the effective address and its high byte is stored at the effective address plus one.


===== Cycle Penalties =====
===== Cycle Penalties =====
* In all [[addressing modes]], STA takes one additional cycle when the accumulator is 16 bits wide.
* In all [[addressing modes]], STA takes one extra 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.
* In [[direct page addressing]] modes, STA takes another extra cycle if the low byte of the [[direct page register]] is nonzero.


=== See Also ===
=== See Also ===

Revision as of 00:15, 27 November 2023

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. If the accumulator is 16 bits wide, its low byte is stored at the effective address and its high byte is stored at the effective address plus one.

Cycle Penalties

See Also

External Links

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