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CPY: Difference between revisions
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'''CPY''' (Compare Y) is a 65x instruction that compares the value of the [[Y index register]]. | '''CPY''' (Compare Y) is a 65x instruction that compares the value of the [[Y index register]]. Internally, this is done via a subtraction, but the difference is not stored anywhere. The contents at the effective address and the Y index register both remain unchanged. | ||
CPY assumes its operands are unsigned. | |||
=== See Also === | === See Also === | ||
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* [[Eyes & Lichty]] page 450, on CPY: https://archive.org/details/0893037893ProgrammingThe65816/page/n476 | * [[Eyes & Lichty]] page 450, on CPY: https://archive.org/details/0893037893ProgrammingThe65816/page/n476 | ||
* [[Labiak]] page 137 on CPY: https://archive.org/details/Programming_the_65816/page/n147 | * [[Labiak]] page 137 on CPY: https://archive.org/details/Programming_the_65816/page/n147 | ||
* [[MCS6500 Manual]] page on CPY: https://archive.org/details/mos_microcomputers_programming_manual/page/n117 | * [[MCS6500 Manual]] page 99 on CPY: https://archive.org/details/mos_microcomputers_programming_manual/page/n117 | ||
* [[Carr]] page 257 on CPY: https://archive.org/details/6502UsersManual/page/n270 | * [[Carr]] page 257 on CPY: https://archive.org/details/6502UsersManual/page/n270 | ||
* [[Leventhal]] page 3-59 on CPY: https://archive.org/details/6502-assembly-language-programming/page/n108 | * [[Leventhal]] page 3-59 on CPY: https://archive.org/details/6502-assembly-language-programming/page/n108 | ||
Latest revision as of 07:51, 19 December 2023
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Immediate | C0 | 2 bytes* | 2 cycles* | ||||
| Absolute | CC | 3 bytes | 4 cycles* | ||||
| Direct Page | C4 | 2 bytes | 3 cycles* | ||||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| N | V | M | X | D | I | Z | C | |
| . | . | . | . | . | ||||
CPY (Compare Y) is a 65x instruction that compares the value of the Y index register. Internally, this is done via a subtraction, but the difference is not stored anywhere. The contents at the effective address and the Y index register both remain unchanged.
CPY assumes its operands are unsigned.
See Also
External Links
- Eyes & Lichty page 450, on CPY: https://archive.org/details/0893037893ProgrammingThe65816/page/n476
- Labiak page 137 on CPY: https://archive.org/details/Programming_the_65816/page/n147
- MCS6500 Manual page 99 on CPY: https://archive.org/details/mos_microcomputers_programming_manual/page/n117
- Carr page 257 on CPY: https://archive.org/details/6502UsersManual/page/n270
- Leventhal page 3-59 on CPY: https://archive.org/details/6502-assembly-language-programming/page/n108
- snes9x implementation of CPY: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L442
- undisbeliever on CPY: https://undisbeliever.net/snesdev/65816-opcodes.html#cpy-compare-index-register-y-with-memory