Memory/Accumulator Select: Difference between revisions

Revision as of 00:45, 10 August 2024

The Memory/Accumulator Select (M) flag is bit 5 of the 65c816's processor status register. It indicates whether the accumulator is 8 or 16 bits wide:

When clear, the accumulator is 16 bits wide. It can only be clear in native mode.
When set, the accumulator is 8 bits wide, but the high byte (B) is still retained. This is the case after reset because the processor is in emulation mode.

It can be affected by:

It affects the behavior of (possibly incomplete list):

But it does not affect XBA, TDC, or TCD.

There are no BMS or BMC instructions that examine this flag.

Revision as of 23:14, 9 August 2024 (view source) Xetheria (talk \| contribs) (ORA, AND, EOR) ← Older edit		Revision as of 00:45, 10 August 2024 (view source) Xetheria (talk \| contribs) (shorten sentence) Newer edit →
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	The '''Memory/Accumulator Select''' (M) flag ~~exists in~~ the [[~~processor status register~~]] ~~(bit 5) of the~~ [[~~65c816~~]]. It indicates whether the [[accumulator]] is 8 or 16 bits wide:		The '''Memory/Accumulator Select''' (M) flag is bit 5 of the [[65c816]]'s [[processor status register]]. It indicates whether the [[accumulator]] is 8 or 16 bits wide:

	* When clear, the accumulator is 16 bits wide. It can only be clear in [[native mode]].		* When clear, the accumulator is 16 bits wide. It can only be clear in [[native mode]].