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STX: Difference between revisions
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'''STX''' (Store X) is a 65x instruction that stores the value of the [[X index register]]. | '''STX''' (Store X) is a 65x instruction that stores the value of the [[X index register]]. | ||
No flags are affected. | |||
===== Cycle Penalties ===== | ===== Cycle Penalties ===== | ||
Revision as of 21:17, 6 July 2024
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Absolute | 8E | 3 bytes | 4 cycles* | ||||
| Direct Page | 86 | 2 bytes | 3 cycles* | ||||
| Direct Page Indexed by Y | 96 | 2 bytes | 4 cycles* | ||||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| N | V | M | X | D | I | Z | C | |
| . | . | . | . | . | . | . | . | |
STX (Store X) is a 65x instruction that stores the value of the X index register.
No flags are affected.
Cycle Penalties
- STX takes one additional cycle when the index registers are 16 bits wide, in all addressing modes.
- In both direct page addressing modes only, STX takes another additional cycle if the low byte of the direct page register is nonzero.
See Also
External Links
- Eyes & Lichty page 505, on STX: https://archive.org/details/0893037893ProgrammingThe65816/page/n531
- Labiak page 186 on STX: https://archive.org/details/Programming_the_65816/page/n196
- MCS6500 Manual page 97 on STX: https://archive.org/details/mos_microcomputers_programming_manual/page/n115
- Carr page 274 on STX: https://archive.org/details/6502UsersManual/page/n287
- Leventhal page 3-97 on STX: https://archive.org/details/6502-assembly-language-programming/page/n146
- snes9x implementation of STX: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1287
- undisbeliever on STX: https://undisbeliever.net/snesdev/65816-opcodes.html#stx-store-index-register-x-to-memory