We've just updated MediaWiki and its underlying software. If anything doesn't look or work quite right, please mention it to us. --RanAS
WDM: Difference between revisions
From SnesLab
(Addressing mode descibed in datasheet) |
|||
| (2 intermediate revisions by the same user not shown) | |||
| Line 38: | Line 38: | ||
=== Trivia === | === Trivia === | ||
* WDM is the only [[implied addressing]] instruction that is more than one | * WDM is the only [[implied addressing]] instruction that is more than one byte long | ||
* The [[Labiak]] textbook does not describe the WDM instruction. | * The [[Labiak]] textbook does not describe the WDM instruction. | ||
| Line 54: | Line 54: | ||
[[Category:65c816 additions]] | [[Category:65c816 additions]] | ||
[[Category:Two-byte Instructions]] | [[Category:Two-byte Instructions]] | ||
[[Category:Implied Instructions]] | |||
[[Category:Two-cycle Instructions]] | |||
Latest revision as of 11:39, 14 December 2023
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Implied (type 3)[4] | 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
- WDM is the only implied addressing instruction that is more than one byte long
- The Labiak textbook does not describe the WDM instruction.
See Also
External Links
- Eyes & Lichty page 523, 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
- Table 5-4 Opcode Matrix of official 65c816 datasheet