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CPX
From SnesLab
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Immediate | E0 | 2/3 bytes | 2 cycles* | ||||
| Absolute | EC | 3 bytes | 4 cycles* | ||||
| Direct Page | E4 | 2 bytes | 3 cycles* | ||||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| N | V | M | X | D | I | Z | C | |
| . | . | . | . | . | ||||
CPX (Compare X) is a 65x instruction that compares the value of the X index register. Internally, this is done via a subtraction, but the difference is not stored anywhere. The index register X is the minuend. The contents at the effective address (when not using immediate data) and the X index register both remain unchanged.
CPX assumes its operands are unsigned.
Syntax
CPX #const CPX addr CPX dp
Cycle Penalties
TODO
See Also
External Links
- Eyes & Lichty page 449, on CPX: https://archive.org/details/0893037893ProgrammingThe65816/page/449
- Labiak page 136 on CPX: https://archive.org/details/Programming_the_65816/page/n146
- MCS6500 Manual page 99 on CPX: https://archive.org/details/mos_microcomputers_programming_manual/page/n117
- Carr page 256 on CPX: https://archive.org/details/6502UsersManual/page/n269
- Leventhal page 3-58 on CPX: https://archive.org/details/6502-assembly-language-programming/page/n107
- snes9x implementation of CPX: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L402
- undisbeliever on CPX: https://undisbeliever.net/snesdev/65816-opcodes.html#cpx-compare-index-register-x-with-memory
- Pickens, John. http://www.6502.org/tutorials/6502opcodes.html#CPX