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WDM: Difference between revisions
From SnesLab
(linkify signature byte) |
(official 65c816 datasheet says WDM is implied admode) |
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Revision as of 20:42, 24 July 2023
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Implied (type 3) | 42 | 2 byte | 2 cycles | ||||
| Flags Affected | |||||||
|---|---|---|---|---|---|---|---|
| N | V | M | X | D | I | Z | C |
| . | . | . | . | . | . | . | . |
WDM (the initials of William David Mensch, the designer of the 65c816) is an instruction that reserves its signature byte for future expansion of the instruction set. None of these extra 256 opcodes were ever implemented, so WDM functions essentially as a two-byte NOP.
Trivia
The Labiak textbook does not describe the WDM instruction.
See Also
External Links
- Eyes & Lichty page on WDM: https://archive.org/details/0893037893ProgrammingThe65816/page/n549
- snes9x implementation of WDM: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L3335
- undisbeliever on WDM: https://undisbeliever.net/snesdev/65816-opcodes.html#wdm-reserved-for-future-expansion