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DEC (SPC700): Difference between revisions
From SnesLab
(→See Also: DEX, DEY) |
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|'''Speed''' | |'''Speed''' | ||
|+ | |+ | ||
| | |[[Accumulator Addressing | Accumulator]] | ||
|9C | |9C | ||
|1 byte | |1 byte | ||
|2 cycles | |2 cycles | ||
|+ | |+ | ||
| | |[[Direct Page Addressing | Direct Page]] | ||
|8B | |8B | ||
|2 | |2 bytes | ||
|4 cycles | |4 cycles | ||
|+ | |+ | ||
| | |[[Direct Page Indexed by X]] | ||
|9B | |9B | ||
|2 | |2 bytes | ||
|5 cycles | |5 cycles | ||
|+ | |+ | ||
| | |[[Absolute Addressing | Absolute]] | ||
|8C | |8C | ||
|3 bytes | |3 bytes | ||
|5 cycles | |5 cycles | ||
|+ | |+ | ||
| | |[[Implied]] (type 1) | ||
|1D | |1D | ||
|1 byte | |1 byte | ||
|2 cycles | |2 cycles | ||
|+ | |+ | ||
| | |[[Implied]] (type 1) | ||
|DC | |DC | ||
|1 byte | |1 byte | ||
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{| class="wikitable" style="float:right;clear:right;width:30%" | {| class="wikitable" style="float:right;clear:right;width:30%" | ||
!colspan="8"|Flags | !colspan="8"|Flags Affected | ||
|+ | |||
|[[Negative Flag|N]] | |||
|[[Overflow Flag|V]] | |||
|[[Direct Page Flag|P]] | |||
|[[Break Flag|B]] | |||
|[[Half-Carry Flag|H]] | |||
|[[Interrupt Enable Flag|I]] | |||
|[[Zero Flag|Z]] | |||
|[[Carry Flag|C]] | |||
|+ | |+ | ||
|N | |N | ||
|. | |. | ||
|. | |. | ||
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|. | |. | ||
|. | |. | ||
|Z | |||
|. | |. | ||
|} | |} | ||
'''DEC''' is an [[SPC700]] instruction that decrements its operand. | '''DEC''' is an [[SPC700]] instruction that decrements its operand by one. | ||
==== Syntax ==== | |||
<pre> | |||
DEC A | |||
DEC dp | |||
DEC dp+X | |||
DEC !abs | |||
DEC X | |||
DEC Y | |||
</pre> | |||
The above are official, but some people prefer alternate mnemonics like: | |||
<pre> | |||
DEA | |||
DEX | |||
DEY | |||
</pre> | |||
=== See Also === | === See Also === | ||
| Line 67: | Line 85: | ||
* [[DEX]] | * [[DEX]] | ||
* [[DEY]] | * [[DEY]] | ||
* [[SBC (SPC700)]] | |||
* [[SBC]] | |||
=== External Links === | === External Links === | ||
* Official Super Nintendo development manual on DEC: [https://archive.org/details/SNESDevManual/book1/page/n232 Appendix C-7 of Book I] | * Official Super Nintendo development manual on DEC: [https://archive.org/details/SNESDevManual/book1/page/n232 Appendix C-7 of Book I] | ||
* anomie: https://github.com/yupferris/TasmShiz/blob/8fabc9764c33a7ae2520a76d80ed7220bb939f12/spc700.txt#L415 | |||
[[Category:ASM]] | [[Category:ASM]] | ||
[[Category:SPC700]] | [[Category:SPC700]] | ||
[[Category:Addition and Subtraction Commands]] | [[Category:Addition and Subtraction Commands]] | ||
Latest revision as of 13:57, 30 July 2024
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Accumulator | 9C | 1 byte | 2 cycles | ||||
| Direct Page | 8B | 2 bytes | 4 cycles | ||||
| Direct Page Indexed by X | 9B | 2 bytes | 5 cycles | ||||
| Absolute | 8C | 3 bytes | 5 cycles | ||||
| Implied (type 1) | 1D | 1 byte | 2 cycles | ||||
| Implied (type 1) | DC | 1 byte | 2 cycles | ||||
| Flags Affected | |||||||
|---|---|---|---|---|---|---|---|
| N | V | P | B | H | I | Z | C |
| N | . | . | . | . | . | Z | . |
DEC is an SPC700 instruction that decrements its operand by one.
Syntax
DEC A DEC dp DEC dp+X DEC !abs DEC X DEC Y
The above are official, but some people prefer alternate mnemonics like:
DEA DEX DEY
See Also
External Links
- Official Super Nintendo development manual on DEC: Appendix C-7 of Book I
- anomie: https://github.com/yupferris/TasmShiz/blob/8fabc9764c33a7ae2520a76d80ed7220bb939f12/spc700.txt#L415