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|'''Speed'''
|'''Speed'''
|+
|+
|immediate
|[[Immediate]]
|49
|49
|2 bytes
|2/3 bytes
|2 cycles*
|2 cycles*
|+
|+
|absolute
|[[Absolute]]
|4D
|4D
|3 bytes
|3 bytes
|4 cycles*
|4 cycles*
|+
|+
|absolute long
|[[Absolute Long Addressing|Absolute Long]]
|4F
|4F
|4 bytes
|4 bytes
|5 cycles*
|5 cycles*
|+
|+
|direct page
|[[Direct Page Addressing|Direct Page]]
|45
|45
|2 bytes
|2 bytes
|3 cycles*
|3 cycles*
|+
|+
|direct page indirect
|[[Direct Page Indirect]]
|52
|52
|2 bytes
|2 bytes
|5 cycles*
|5 cycles*
|+
|+
|direct page indirect long
|[[Direct Page Indirect Long]]
|47
|47
|2 bytes
|2 bytes
|6 cycles*
|6 cycles*
|+
|+
|absolute indexed by X
|[[Absolute Indexed by X]]
|5D
|5D
|3 bytes
|3 bytes
|4 cycles*
|4 cycles*
|+
|+
|absolute long indexed by X
|[[Absolute Long Indexed by X]]
|5F
|5F
|4 bytes
|4 bytes
|5 cycles*
|5 cycles*
|+
|+
|absolute indexed by Y
|[[Absolute Indexed by Y]]
|59
|59
|3 bytes
|3 bytes
|4 cycles*
|4 cycles*
|+
|+
|direct page indexed by X
|[[Direct Page Indexed by X]]
|55
|55
|2 bytes
|2 bytes
|4 cycles*
|4 cycles*
|+
|+
|direct page indexed indirect by X
|[[Direct Page Indexed Indirect by X]]
|41
|41
|2 bytes
|2 bytes
|6 cycles*
|6 cycles*
|+
|+
|direct page indirect indexed by Y
|[[Direct Page Indirect Indexed by Y]]
|51
|51
|2 bytes
|2 bytes
|5 cycles*
|5 cycles*
|+
|+
|direct page indirect long indexed by Y
|[[Direct Page Indirect Long Indexed by Y]]
|57
|57
|2 bytes
|2 bytes
|6 cycles*
|6 cycles*
|+
|+
|stack relative
|[[Stack Relative]]
|43
|43
|2 bytes
|2 bytes
|4 cycles*
|4 cycles*
|+
|+
|stack relative indirect indexed by Y
|[[Stack Relative Indirect Indexed by Y]]
|53
|53
|2 bytes
|2 bytes
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{| class="wikitable" style="float:right;clear:right;width:30%"
{| class="wikitable" style="float:right;clear:right;width:30%"
!colspan="8"|Flags Affected
!colspan="8"|Flags Affected
|+
|[[Negative Flag|N]]
|[[Overflow Flag|V]]
|[[M Flag|M]]
|[[X Flag|X]]
|[[Decimal Flag|D]]
|[[I Flag|I]]
|[[Zero Flag|Z]]
|[[Carry Flag|C]]
|+
|+
|N
|N
|V
|M
|X
|D
|I
|Z
|C
|+
|
|.
|.
|.
|.
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|.
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|.
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|Z
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|}
|}


'''EOR''' is a 65x instruction that performs an [https://mathworld.wolfram.com/XOR.html exclusive or].  In all [[addressing modes]], EOR takes one extra cycle when the accumulator is 16 bits wide.
'''EOR''' is a 65x instruction that performs a bitwise [https://mathworld.wolfram.com/XOR.html exclusive or] between its operand and the accumulator.  The sum is stored in the [[accumulator]].  The size of the accumulator determines whether 8 or 16 bits are EORed.
 
==== Syntax ====
<pre>
EOR #const
EOR addr
EOR long
EOR dp
EOR (dp)
EOR [dp]
EOR addr, X
EOR long, X
EOR addr, Y
EOR dp, X
EOR (dp, X)
EOR (dp), Y
EOR [dp], Y
EOR sr, S
EOR (sr, S), Y
</pre>
 
One example usage of EOR is to flip all the bits of the accumulator:<sup>[10]</sup>
 
<pre>
EOR #$FFFF
</pre>
 
==== Cycle Penalties ====
* In all [[addressing modes]], EOR takes one extra cycle when the accumulator is 16 bits wide.
* In [[direct page addressing]] modes, EOR takes one additional cycle if the low byte of the [[direct page register]] is nonzero.
* In both [[Absolute Indexed]] and DP Indirect Indexed, Y admodes, EOR takes an extra cycle if adding the index crosses a page boundary.


=== See Also ===
=== See Also ===
* [[ORA]]
* [[ORA]]
* [[AND]]
* [[EOR (SPC700)]]
* [[EOR (SPC700)]]
* [[OR (SPC700)]]
* [[XOR (Super FX)]]
* [[XOR (Super FX)]]


=== External Links ===
=== External Links ===
* [[Eyes & Lichty]] page on EOR: https://archive.org/details/0893037893ProgrammingThe65816/page/n480
# [[Eyes & Lichty]], [https://archive.org/details/0893037893ProgrammingThe65816/page/454 page 454] on EOR
* [[Labiak]] page on EOR: https://archive.org/details/Programming_the_65816/page/n151
# [[Labiak]], [https://archive.org/details/Programming_the_65816/page/n151 page 141] on EOR
* [[MCS6500 Manual]] page on EOR: https://archive.org/details/mos_microcomputers_programming_manual/page/n36
# 2.2.4.3 on [[MCS6500 Manual]], [https://archive.org/details/mos_microcomputers_programming_manual/page/n36 page 21] on EOR
* [[Carr]] page on EOR: https://archive.org/details/6502UsersManual/page/n272
# [[Carr]], [https://archive.org/details/6502UsersManual/page/n272 page 259] on EOR
* [[Leventhal]] page on EOR: https://archive.org/details/6502-assembly-language-programming/page/n112
# [[Leventhal]], [https://archive.org/details/6502-assembly-language-programming/page/n112 page 3-63] on EOR
* snes9x implementation of EOR: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L533
# snes9x implementation of EOR: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L533
* undisbeliever on EOR: https://undisbeliever.net/snesdev/65816-opcodes.html#eor-exclusive-or-accumulator-with-memory
# undisbeliever on EOR: https://undisbeliever.net/snesdev/65816-opcodes.html#eor-exclusive-or-accumulator-with-memory
# Pickens, John. http://www.6502.org/tutorials/6502opcodes.html#EOR
# Clark, Bruce. http://www.6502.org/tutorials/65c816opcodes.html#6.1.2.1
# Carr, [https://archive.org/details/6502UsersManual/page/n273 page 260]


[[Category:ASM]]
[[Category:ASM]]
[[Category:Group One Instructions]]
[[Category:Group One Instructions]]
[[Category:Inherited from 6502]]
[[Category:Inherited from 6502]]

Latest revision as of 17:46, 23 August 2024

Basic Info
Addressing Mode Opcode Length Speed
Immediate 49 2/3 bytes 2 cycles*
Absolute 4D 3 bytes 4 cycles*
Absolute Long 4F 4 bytes 5 cycles*
Direct Page 45 2 bytes 3 cycles*
Direct Page Indirect 52 2 bytes 5 cycles*
Direct Page Indirect Long 47 2 bytes 6 cycles*
Absolute Indexed by X 5D 3 bytes 4 cycles*
Absolute Long Indexed by X 5F 4 bytes 5 cycles*
Absolute Indexed by Y 59 3 bytes 4 cycles*
Direct Page Indexed by X 55 2 bytes 4 cycles*
Direct Page Indexed Indirect by X 41 2 bytes 6 cycles*
Direct Page Indirect Indexed by Y 51 2 bytes 5 cycles*
Direct Page Indirect Long Indexed by Y 57 2 bytes 6 cycles*
Stack Relative 43 2 bytes 4 cycles*
Stack Relative Indirect Indexed by Y 53 2 bytes 7 cycles*
Flags Affected
N V M X D I Z C
N . . . . . Z .

EOR is a 65x instruction that performs a bitwise exclusive or between its operand and the accumulator. The sum is stored in the accumulator. The size of the accumulator determines whether 8 or 16 bits are EORed.

Syntax

EOR #const
EOR addr
EOR long
EOR dp
EOR (dp)
EOR [dp]
EOR addr, X
EOR long, X
EOR addr, Y
EOR dp, X
EOR (dp, X)
EOR (dp), Y
EOR [dp], Y
EOR sr, S
EOR (sr, S), Y

One example usage of EOR is to flip all the bits of the accumulator:[10] 

EOR #$FFFF

Cycle Penalties

See Also

External Links

  1. Eyes & Lichty, page 454 on EOR
  2. Labiak, page 141 on EOR
  3. 2.2.4.3 on MCS6500 Manual, page 21 on EOR
  4. Carr, page 259 on EOR
  5. Leventhal, page 3-63 on EOR
  6. snes9x implementation of EOR: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L533
  7. undisbeliever on EOR: https://undisbeliever.net/snesdev/65816-opcodes.html#eor-exclusive-or-accumulator-with-memory
  8. Pickens, John. http://www.6502.org/tutorials/6502opcodes.html#EOR
  9. Clark, Bruce. http://www.6502.org/tutorials/65c816opcodes.html#6.1.2.1
  10. Carr, page 260
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