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DEY: Difference between revisions
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!colspan="8"|Basic Info | !colspan="8"|Basic Info | ||
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|'''Speed''' | |'''Speed''' | ||
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| | |[[Implied]] (type 1) | ||
|88 | |88 | ||
|1 byte | |1 byte | ||
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!colspan="8"|Flags | !colspan="8"|Flags Affected | ||
|+ | |||
|[[N Flag|N]] | |||
|[[V Flag|V]] | |||
|[[M Flag|M]] | |||
|[[X Flag|X]] | |||
|[[D Flag|D]] | |||
|[[I Flag|I]] | |||
|[[Z Flag|Z]] | |||
|[[C Flag|C]] | |||
|+ | |+ | ||
|N | |N | ||
|. | |. | ||
|. | |. | ||
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|. | |. | ||
|. | |. | ||
| | |Z | ||
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|} | |} | ||
'''DEY''' is a 65x instruction that decrements the [[Y index register]] by one. DEY ignores the [[decimal flag]]. Unlike [[SBC]], DEY never affects the [[carry flag]]. | |||
==== Syntax ==== | |||
<pre> | |||
DEY | |||
</pre> | |||
=== See Also === | === See Also === | ||
* [[DEC]] | |||
* [[DEX]] | * [[DEX]] | ||
* [[INX]] | * [[INX]] | ||
* [[INY]] | * [[INY]] | ||
* [[DEC (SPC700)]] | |||
* [[DEC (Super FX)]] | |||
=== External Links === | === External Links === | ||
* [[Eyes & Lichty]] | * [[Eyes & Lichty]], [https://archive.org/details/0893037893ProgrammingThe65816/page/453 page 453] on DEY | ||
* [[Labiak]] | * [[Labiak]], [https://archive.org/details/Programming_the_65816/page/n150 page 140] on DEY | ||
* [[MCS6500 Manual]] | * 7.7 on [[MCS6500 Manual]], [https://archive.org/details/mos_microcomputers_programming_manual/page/n116 page 98] on DEY | ||
* [[Carr]] | * [[Carr]], [https://archive.org/details/6502UsersManual/page/n271 page 258] on DEY | ||
* [[Leventhal]] | * [[Leventhal]], [https://archive.org/details/6502-assembly-language-programming/page/n111 page 3-62] on DEY | ||
* snes9x implementation of DEY: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1514 | * snes9x implementation of DEY: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1514 | ||
* Clark, Bruce. http://www.6502.org/tutorials/65c816opcodes.html#6.1.1.3 | |||
[[Category:ASM]] | [[Category:ASM]] | ||
[[Category:Inherited from 6502]] | [[Category:Inherited from 6502]] | ||
[[Category:One-byte Instructions]] | |||
[[Category:Implied Instructions]] | |||
[[Category:Two-cycle Instructions]] | |||
Latest revision as of 20:09, 12 August 2024
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Implied (type 1) | 88 | 1 byte | 2 cycles | ||||
| Flags Affected | |||||||
|---|---|---|---|---|---|---|---|
| N | V | M | X | D | I | Z | C |
| N | . | . | . | . | . | Z | . |
DEY is a 65x instruction that decrements the Y index register by one. DEY ignores the decimal flag. Unlike SBC, DEY never affects the carry flag.
Syntax
DEY
See Also
External Links
- Eyes & Lichty, page 453 on DEY
- Labiak, page 140 on DEY
- 7.7 on MCS6500 Manual, page 98 on DEY
- Carr, page 258 on DEY
- Leventhal, page 3-62 on DEY
- snes9x implementation of DEY: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1514
- Clark, Bruce. http://www.6502.org/tutorials/65c816opcodes.html#6.1.1.3