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BEQ: Difference between revisions

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|'''Speed'''
|'''Speed'''
|+
|+
|relative
|[[Program Counter Relative]]
|F0
|F0
|2 byte
|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 Clobbered
!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.
 
No flags are affected.
 
==== Syntax ====
<pre>
BEQ nearlabel
</pre>
 
==== 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 ===
=== See Also ===
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=== External Links ===
=== External Links ===
* [[Eyes & Lichty]] page on BEQ: https://archive.org/details/0893037893ProgrammingThe65816/page/n456
* [[Eyes & Lichty]], [https://archive.org/details/0893037893ProgrammingThe65816/page/430 page 430] on BEQ
* [[Labiak]] page on BEQ: https://archive.org/details/Programming_the_65816/page/n130
* [[Labiak]], [https://archive.org/details/Programming_the_65816/page/n130 page 120] on BEQ
* [[MCS6500 Manual]] page on BEQ: https://archive.org/details/mos_microcomputers_programming_manual/page/n56
* 4.1.2.5 on [[MCS6500 Manual]], [https://archive.org/details/mos_microcomputers_programming_manual/page/n56 page 41] on BEQ
* [[Carr]] page on BEQ: https://archive.org/details/6502UsersManual/page/n262
* [[Carr]], [https://archive.org/details/6502UsersManual/page/n262 page 249] on BEQ
* [[Leventhal]] page on BEQ: https://archive.org/details/6502-assembly-language-programming/page/n93
* [[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


[[Category:ASM]]
[[Category:ASM]]
[[Category:Inherited from 6502]]
[[Category:Inherited from 6502]]
[[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