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STA
From SnesLab
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.
Cycle Penalties
- 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
External Links
- Eyes & Lichty page 503, 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