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STY
From SnesLab
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Absolute | 8C | 3 bytes | 4 cycles* | ||||
| Direct Page | 84 | 2 bytes | 3 cycles* | ||||
| direct page indexed Y | 96 | 2 bytes | 4 cycles* | ||||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| N | V | M | X | D | I | Z | C | |
| . | . | . | . | . | . | . | . | |
STY (Store Y) is a 65x instruction that stores the value of the Y index register.
Cycle Penalties
- STY takes one additional cycle when the index registers are 16 bits wide, in all addressing modes.
- In both direct page addressing modes only, STY takes another additional cycle if the low byte of the direct page register is nonzero.
See Also
External Links
- Eyes & Lichty page 506, on STY: https://archive.org/details/0893037893ProgrammingThe65816/page/n532
- Labiak page 187 on STY: https://archive.org/details/Programming_the_65816/page/n197
- MCS6500 Manual page 97 on STY: https://archive.org/details/mos_microcomputers_programming_manual/page/n115
- Carr page 274 on STY: https://archive.org/details/6502UsersManual/page/n287
- Leventhal page 3-98 on STY: https://archive.org/details/6502-assembly-language-programming/page/n147
- snes9x implementation of STY: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1302
- undisbeliever on STY: https://undisbeliever.net/snesdev/65816-opcodes.html#sty-store-index-register-y-to-memory