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BCS: Difference between revisions
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{| class="wikitable" style="float:right;clear:right;width:40%" | |||
{| class="wikitable" style="float:right;clear:right;width: | |||
!colspan="8"|Basic Info | !colspan="8"|Basic Info | ||
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|'''Speed''' | |'''Speed''' | ||
|+ | |+ | ||
| | |[[Program Counter Relative]] | ||
|B0 | |B0 | ||
|2 | |2 bytes | ||
|2 cycles | |2 cycles | ||
|} | |} | ||
{| class="wikitable" style="float:right;clear:right;width:30%" | {| class="wikitable" style="float:right;clear:right;width:30%" | ||
!colspan="9"|Flags | !colspan="9"|Flags Affected | ||
|+ | |+ | ||
|N | |[[Negative Flag|N]] | ||
|V | |[[Overflow Flag|V]] | ||
|M | |[[M Flag|M]] | ||
|X | |[[X Flag|X]] | ||
|D | |[[Decimal Flag|D]] | ||
|I | |[[I Flag|I]] | ||
|Z | |[[Zero Flag|Z]] | ||
|C | |[[Carry Flag|C]] | ||
|+ | |+ | ||
|. | |. | ||
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|. | |. | ||
|} | |} | ||
'''BCS''' (Branch if Carry Set) is a 65x instruction that performs a jump if the [[carry flag]] is set. An alternate mnemonic is "BGE." | |||
If carry is clear, control simply falls through to the next instruction. | |||
No flags are affected. | |||
==== Syntax ==== | |||
<pre> | |||
BCS nearlabel | |||
BGE nearlabel | |||
</pre> | |||
==== Cycle Penalties ==== | |||
* BCS takes one additional cycle if the branch is taken | |||
* BCS takes another extra cycle in [[emulation mode]] if that branch taken crosses a page boundary. | |||
=== See Also === | === See Also === | ||
* [[BCC]] | * [[BCC]] | ||
* [[BVC]] | |||
* [[BVS]] | |||
* [[XCE]] | |||
* [[BCS (Super FX)]] | |||
* [[BGE (Super FX)]] | |||
=== External Links === | |||
* [[Eyes & Lichty]], [https://archive.org/details/0893037893ProgrammingThe65816/page/429 page 429] on BCS | |||
* [[Labiak]], [https://archive.org/details/Programming_the_65816/page/n129 page 119] on BCS | |||
* 4.1.2.4 on [[MCS6500 Manual]], [https://archive.org/details/mos_microcomputers_programming_manual/page/n55 page 40] on BCS | |||
* [[Carr]], [https://archive.org/details/6502UsersManual/page/n261 page 248] on BCS | |||
* [[Leventhal]], [https://archive.org/details/6502-assembly-language-programming/page/n93 page 3-44] on BCS | |||
* snes9x implementation of BCS: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1365 | |||
[[Category:ASM]] | [[Category:ASM]] | ||
[[Category:Inherited from 6502]] | |||
[[Category:Conditional Branches]] | |||
[[Category:Two-byte Instructions]] | |||
[[Category:Two-cycle Instructions]] | |||
Latest revision as of 02:39, 10 August 2024
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Program Counter Relative | B0 | 2 bytes | 2 cycles | ||||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| N | V | M | X | D | I | Z | C | |
| . | . | . | . | . | . | . | . | |
BCS (Branch if Carry Set) is a 65x instruction that performs a jump if the carry flag is set. An alternate mnemonic is "BGE."
If carry is clear, control simply falls through to the next instruction.
No flags are affected.
Syntax
BCS nearlabel BGE nearlabel
Cycle Penalties
- BCS takes one additional cycle if the branch is taken
- BCS takes another extra cycle in emulation mode if that branch taken crosses a page boundary.
See Also
External Links
- Eyes & Lichty, page 429 on BCS
- Labiak, page 119 on BCS
- 4.1.2.4 on MCS6500 Manual, page 40 on BCS
- Carr, page 248 on BCS
- Leventhal, page 3-44 on BCS
- snes9x implementation of BCS: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1365