EOR: Difference between revisions

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

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.

External Links

Eyes & Lichty, page 454 on EOR
Labiak, page 141 on EOR
2.2.4.3 on MCS6500 Manual, page 21 on EOR
Carr, page 259 on EOR
Leventhal, page 3-63 on EOR
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
Pickens, John. http://www.6502.org/tutorials/6502opcodes.html#EOR
Clark, Bruce. http://www.6502.org/tutorials/65c816opcodes.html#6.1.2.1
Carr, page 260

@@ Line 1: / Line 1: @@
-'''EOR''' is a 65x instruction that performs an [https://mathworld.wolfram.com/XOR.html exclusive or].
+{| class="wikitable" style="float:right;clear:right;width:50%"
+!colspan="8"|Basic Info
+|+
+|'''Addressing Mode'''
+|'''Opcode'''
+|'''Length'''
+|'''Speed'''
+|+
+|[[Immediate]]
+|49
+|2/3 bytes
+|2 cycles*
+|+
+|[[Absolute]]
+|4D
+|3 bytes
+|4 cycles*
+|+
+|[[Absolute Long Addressing|Absolute Long]]
+|4F
+|4 bytes
+|5 cycles*
+|+
+|[[Direct Page Addressing|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*
+|}
 {| class="wikitable" style="float:right;clear:right;width:30%"
-!colspan="8"|Flags Clobbered
+!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
-|V
-|M
-|X
-|D
-|I
-|Z
-|C
-|+
-|
 |.
 |.
@@ Line 19: / Line 101: @@
 |.
 |.
-|
+|Z
 |.
 |}
+'''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 ===
 * [[ORA]]
+* [[AND]]
+* [[EOR (SPC700)]]
+* [[OR (SPC700)]]
+* [[XOR (Super FX)]]
+=== External Links ===
+# [[Eyes & Lichty]], [https://archive.org/details/0893037893ProgrammingThe65816/page/454 page 454] on EOR
+# [[Labiak]], [https://archive.org/details/Programming_the_65816/page/n151 page 141] on EOR
+# 2.2.4.3 on [[MCS6500 Manual]], [https://archive.org/details/mos_microcomputers_programming_manual/page/n36 page 21] on EOR
+# [[Carr]], [https://archive.org/details/6502UsersManual/page/n272 page 259] on EOR
+# [[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
+# 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:Group One Instructions]]
+[[Category:Inherited from 6502]]