Accumulator

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

• ADC
• SBC
• LDA
• STA
• PHA
• PLA
• TAX
• TAY
• TXA
• TYA
• Accumulator Addressing

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