We've just updated MediaWiki and its underlying software. If anything doesn't look or work quite right, please mention it to us. --RanAS

XBA

From SnesLab
Revision as of 15:12, 11 August 2024 by Xetheria (talk | contribs) (XBA only way to access B byte)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search
Basic Info
Addressing Mode Opcode Length Speed
Implied (type 1) EB 1 byte 3 cycles
Flags Affected
N V M X D I Z C
N . . . . . Z .

XBA is a 65c816 instruction that exchanges the high byte (B) and low byte (typically called A) of the C accumulator. It works even in 6502 emulation mode. In 65816 native mode, its standard mnemonic is still "XBA" even when the accumulator is 16-bits wide. An alternative mnemonic is "SWA."

XBA can be used to convert big endian data to little endian and vice versa. XBA appears to be the only way to access the high B byte when the M flag is set.

The negative flag will match the most significant bit of the new low byte (A) of the accumulator. The zero flag will be set if and only if the new low byte (A) of the accumulator is zero, otherwise it is cleared.

Syntax

XBA
SWA

Even though the hidden B byte is colloquially considered to be second accumulator, XBA still isn't considered to use accumulator addressing.

xba.png

See Also

External Links