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DEC: Difference between revisions
From SnesLab
(additional cycles) |
(accumulator admode always takes 2 cycles) |
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|3A | |3A | ||
|1 byte | |1 byte | ||
|2 cycles | |2 cycles | ||
|+ | |+ | ||
|absolute | |absolute | ||
Revision as of 00:14, 20 November 2023
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| accumulator | 3A | 1 byte | 2 cycles | ||||
| absolute | CE | 3 bytes | 6 cycles* | ||||
| direct page | C6 | 2 bytes | 5 cycles* | ||||
| absolute indexed X | DE | 3 bytes | 7 cycles* | ||||
| direct page indexed X | D6 | 2 bytes | 6 cycles* | ||||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| N | V | M | X | D | I | Z | C | |
| . | . | . | . | . | . | |||
DEC (Decrement) is a 65x instruction that decrements the value in the location specified by the operand. Except in accumulator addressing, DEC takes two extra cycles when the accumulator is 16 bits wide.
See Also
External Links
- Eyes & Lichty page on DEC: https://archive.org/details/0893037893ProgrammingThe65816/page/n477
- Labiak page on DEC: https://archive.org/details/Programming_the_65816/page/n148
- MCS6500 Manual page on DEC: https://archive.org/details/mos_microcomputers_programming_manual/page/n176
- Carr page on DEC: https://archive.org/details/6502UsersManual/page/n270
- Leventhal page on DEC: https://archive.org/details/6502-assembly-language-programming/page/n109
- snes9x implementation of DEC: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L482
- undisbeliever on DEC: https://undisbeliever.net/snesdev/65816-opcodes.html#dec-decrement