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

Negative Flag: Difference between revisions

From SnesLab
Jump to: navigation, search
(→‎Reference: hid archive URL)
(more description of LSR)
Line 46: Line 46:
* [[XBA]]
* [[XBA]]


Also, [[LSR]] always clears the negative flag.
Also, [[LSR]] always clears the negative flag because it also shifts a zero into the operand's most significant bit, making it non-negative.


[[BPL]] and [[BMI]] examine the negative flag to decide whether or not to branch.
[[BPL]] and [[BMI]] examine the negative flag to decide whether or not to branch.

Revision as of 22:33, 8 August 2024

The Negative Flag (N) exists on the 65c816 as bit 7 of the status register. Although there are no dedicated SEN or CLN instructions to set or clear it, it can be set with SEP and cleared with REP:

SEP #$80
REP #$80

These instructions also affect the negative flag (this bulleted list being 37 long):

Also, LSR always clears the negative flag because it also shifts a zero into the operand's most significant bit, making it non-negative.

BPL and BMI examine the negative flag to decide whether or not to branch.

See Also

Reference