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Accumulator: Difference between revisions
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An '''Accumulator''' is a very fast register inside a processor that acts as a mathematical scratch pad. | An '''Accumulator''' is a very fast register inside a processor that acts as a mathematical scratch pad. | ||
The [[65c816]]'s accumulator can be either 8 or 16 bits in size, as configured by the | The [[65c816]]'s accumulator can be either 8 or 16 bits in size, as configured by the [[m flag]]. [[Labiak]] calls this 16-bit memory mode. When the [[direct page]] is coincident with the [[zero page]], [[TDC]] is a good way to zero it. | ||
The high byte ("B") is still retained even when the accumulator is 8 bits wide and can be accessed with [[XBA]]. | The high byte ("B") is still retained even when the accumulator is 8 bits wide and can be accessed with [[XBA]]. | ||
Revision as of 00:32, 10 August 2024
An Accumulator is a very fast register inside a processor that acts as a mathematical scratch pad.
The 65c816's accumulator can be either 8 or 16 bits in size, as configured by the m flag. Labiak calls this 16-bit memory mode. When the direct page is coincident with the zero page, TDC is a good way to zero it.
The high byte ("B") is still retained even when the accumulator is 8 bits wide and can be accessed with XBA.
The S-SMP's accumulator is always 8 bits wide.
See Also
References
- Eyes & Lichty, page 27
- subparagraph 8.1.1 A Register on page 3-8-4 of Book II of the official Super Nintendo development manual