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STY: Difference between revisions
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!colspan="9"|Flags Affected | !colspan="9"|Flags Affected | ||
|+ | |+ | ||
|N | |[[Negative Flag|N]] | ||
|V | |[[Overflow Flag|V]] | ||
|M | |[[M Flag|M]] | ||
|X | |[[X Flag|X]] | ||
|D | |[[Decimal Flag|D]] | ||
|I | |[[I Flag|I]] | ||
|Z | |[[Zero Flag|Z]] | ||
|C | |[[Carry Flag|C]] | ||
|+ | |+ | ||
|. | |. | ||
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|} | |} | ||
'''STY''' (Store Y) is a 65x instruction that stores the value of the [[Y index register]]. | '''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 === | === See Also === | ||
* [[LDY]] | |||
* [[STA]] | * [[STA]] | ||
* [[STX]] | * [[STX]] | ||
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=== External Links === | === External Links === | ||
* [[Eyes & Lichty]] page 506, on STY: https://archive.org/details/0893037893ProgrammingThe65816/page/n532 | * [[Eyes & Lichty]] page 506, on STY: https://archive.org/details/0893037893ProgrammingThe65816/page/n532 | ||
* [[Labiak]] page on STY: https://archive.org/details/Programming_the_65816/page/n197 | * [[Labiak]] page 187 on STY: https://archive.org/details/Programming_the_65816/page/n197 | ||
* [[MCS6500 Manual]] page on STY: https://archive.org/details/mos_microcomputers_programming_manual/page/n115 | * [[MCS6500 Manual]] page 97 on STY: https://archive.org/details/mos_microcomputers_programming_manual/page/n115 | ||
* [[Carr]] page on STY: https://archive.org/details/6502UsersManual/page/n287 | * [[Carr]] page 274 on STY: https://archive.org/details/6502UsersManual/page/n287 | ||
* [[Leventhal]] page on STY: https://archive.org/details/6502-assembly-language-programming/page/n147 | * [[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 | * 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 | * undisbeliever on STY: https://undisbeliever.net/snesdev/65816-opcodes.html#sty-store-index-register-y-to-memory | ||
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[[Category:Group Three Instructions]] | [[Category:Group Three Instructions]] | ||
[[Category:Inherited from 6502]] | [[Category:Inherited from 6502]] | ||
[[Category:Load/Store Instructions]] |
Latest revision as of 04:21, 6 December 2023
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