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BEQ: Difference between revisions
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|'''Speed''' | |'''Speed''' | ||
|+ | |+ | ||
| | |[[Program Counter Relative]] | ||
|F0 | |F0 | ||
|2 | |2 bytes | ||
|2 cycles | |2 cycles* | ||
|} | |} | ||
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!colspan="9"|Flags Affected | !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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|} | |} | ||
'''BEQ''' (Branch if Equal) is a 65x instruction that performs a jump if the [[zero flag]] is set. | '''BEQ''' (Branch if Equal) is a 65x instruction that performs a jump if the [[zero flag]] is set. If the zero flag is clear, control simply falls through to the instruction following BEQ. | ||
===== Cycle Penalties | No flags are affected. | ||
==== Syntax ==== | |||
<pre> | |||
BEQ nearlabel | |||
</pre> | |||
==== Cycle Penalties ==== | |||
* BEQ takes an extra cycle if the branch is taken | * BEQ takes an extra cycle if the branch is taken | ||
* BEQ takes another extra cycle if the branch taken crosses a [[page]] boundary in [[emulation mode]] | |||
=== See Also === | === See Also === | ||
| Line 45: | Line 53: | ||
=== External Links === | === External Links === | ||
* [[Eyes & Lichty]] | * [[Eyes & Lichty]], [https://archive.org/details/0893037893ProgrammingThe65816/page/430 page 430] on BEQ | ||
* [[Labiak]] | * [[Labiak]], [https://archive.org/details/Programming_the_65816/page/n130 page 120] on BEQ | ||
* [[MCS6500 Manual]] | * 4.1.2.5 on [[MCS6500 Manual]], [https://archive.org/details/mos_microcomputers_programming_manual/page/n56 page 41] on BEQ | ||
* [[Carr]] | * [[Carr]], [https://archive.org/details/6502UsersManual/page/n262 page 249] on BEQ | ||
* [[Leventhal]] | * [[Leventhal]], [https://archive.org/details/6502-assembly-language-programming/page/n93 page 3-44] on BEQ | ||
* snes9x implementation of BEQ: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1370 | * snes9x implementation of BEQ: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1370 | ||
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[[Category:Inherited from 6502]] | [[Category:Inherited from 6502]] | ||
[[Category:Conditional Branches]] | [[Category:Conditional Branches]] | ||
[[Category:Two-byte Instructions]] | |||
Latest revision as of 17:53, 23 August 2024
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Program Counter Relative | F0 | 2 bytes | 2 cycles* | ||||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| N | V | M | X | D | I | Z | C | |
| . | . | . | . | . | . | . | . | |
BEQ (Branch if Equal) is a 65x instruction that performs a jump if the zero flag is set. If the zero flag is clear, control simply falls through to the instruction following BEQ.
No flags are affected.
Syntax
BEQ nearlabel
Cycle Penalties
- BEQ takes an extra cycle if the branch is taken
- BEQ takes another extra cycle if the branch taken crosses a page boundary in emulation mode
See Also
External Links
- Eyes & Lichty, page 430 on BEQ
- Labiak, page 120 on BEQ
- 4.1.2.5 on MCS6500 Manual, page 41 on BEQ
- Carr, page 249 on BEQ
- Leventhal, page 3-44 on BEQ
- snes9x implementation of BEQ: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1370