We've just updated MediaWiki and its underlying software. If anything doesn't look or work quite right, please mention it to us. --RanAS
SEP: Difference between revisions
From SnesLab
(flowed SED,SEI,SEC into body) |
(clarify what is meant by directly) |
||
Line 49: | Line 49: | ||
'''SEP''' (Set Status Bits) is a [[65c816]] instruction that sets bits in the [[status register]] that correspond to set bits in the operand. | '''SEP''' (Set Status Bits) is a [[65c816]] instruction that sets bits in the [[status register]] that correspond to set bits in the operand. | ||
SEP is the only way to set the m and x flags directly (but [[PLP]] and [[RTI]] may set them too.)<sup>[1]</sup> But, SEP can't modify those two flags in [[emulation mode]] because they are being forced to be set. | SEP is the only way to set the m and x flags directly without disturbing the [[stack]] (but [[PLP]] and [[RTI]] may set them too.)<sup>[1]</sup> But, SEP can't modify those two flags in [[emulation mode]] because they are being forced to be set. | ||
==== Syntax ==== | ==== Syntax ==== |
Revision as of 17:07, 11 August 2024
Basic Info | |||||||
---|---|---|---|---|---|---|---|
Addressing Mode | Opcode | Length | Speed | ||||
Immediate | E2 | 2 bytes | 3 cycles |
Flags Affected | ||||||||
---|---|---|---|---|---|---|---|---|
N | V | M | X | D | I | Z | C | |
emulation mode | N | V | . | . | D | I | Z | C |
native mode | N | V | M | X | D | I | Z | C |
SEP (Set Status Bits) is a 65c816 instruction that sets bits in the status register that correspond to set bits in the operand.
SEP is the only way to set the m and x flags directly without disturbing the stack (but PLP and RTI may set them too.)[1] But, SEP can't modify those two flags in emulation mode because they are being forced to be set.
Syntax
SEP #%nvmxdizc
If you only want to set one flag, SED, SEI, or SEC are smaller/faster than SEP.
See Also
References
- Eyes & Lichty, page 502 on SEP
- Labiak, page 183 on SEP
- snes9x implementation of SEP: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L3203
- undisbeliever on SEP: https://undisbeliever.net/snesdev/65816-opcodes.html#sep-set-status-bits