WDM: Difference between revisions

Revision as of 17:11, 13 July 2023


Basic Info
Addressing Mode	Opcode	Length	Speed
	42	2 byte	2 cycles


Flags Clobbered
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.

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

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-'''WDM''' (the initials of [https://themenschfoundation.org/who-is-william-d-mensch-jr-aka-bill-mensch/ 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]].
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 !colspan="8"|Basic Info
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+'''WDM''' (the initials of [https://themenschfoundation.org/who-is-william-d-mensch-jr-aka-bill-mensch/ 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 ===