CPX: Difference between revisions

Latest revision as of 07:51, 19 December 2023


Basic Info
Addressing Mode	Opcode	Length	Speed
Immediate	E0	2 bytes*	2 cycles*
Absolute	EC	3 bytes	4 cycles*
Direct Page	E4	2 bytes	3 cycles*


Flags Affected
N	V	M	X	D	I	Z	C
	.	.	.	.	.

CPX (Compare X) is a 65x instruction that compares the value of the X index register. Internally, this is done via a subtraction, but the difference is not stored anywhere. The contents at the effective address and the X index register both remain unchanged.

CPX assumes its operands are unsigned.

External Links

Eyes & Lichty page 449, on CPX: https://archive.org/details/0893037893ProgrammingThe65816/page/n475
Labiak page 136 on CPX: https://archive.org/details/Programming_the_65816/page/n146
MCS6500 Manual page 99 on CPX: https://archive.org/details/mos_microcomputers_programming_manual/page/n117
Carr page 256 on CPX: https://archive.org/details/6502UsersManual/page/n269
Leventhal page 3-58 on CPX: https://archive.org/details/6502-assembly-language-programming/page/n107
snes9x implementation of CPX: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L402
undisbeliever on CPX: https://undisbeliever.net/snesdev/65816-opcodes.html#cpx-compare-index-register-x-with-memory

@@ Line 1: / Line 1: @@
-'''CPX''' (Compare X) is a 65x instruction that compares the value of the [[X index register]].
+{| class="wikitable" style="float:right;clear:right;width:40%"
-{| class="wikitable" style="float:right;clear:right;width:30%"
 !colspan="8"|Basic Info
 |+
@@ Line 9: / Line 7: @@
 |'''Speed'''
 |+
-|immediate
+|[[Immediate]]
 |E0
-|2 bytes
+|2 bytes*
-|2 cycles
+|2 cycles*
 |+
-|absolute
+|[[Absolute]]
 |EC
 |3 bytes
-|4 cycles
+|4 cycles*
 |+
-|direct page
+|[[Direct Page Addressing|Direct Page]]
 |E4
 |2 bytes
-|3 cycles
+|3 cycles*
 |}
 {| 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]]
 |+
 |
@@ Line 46: / Line 44: @@
 |
 |}
+'''CPX''' (Compare X) is a 65x instruction that compares the value of the [[X index register]].  Internally, this is done via a subtraction, but the difference is not stored anywhere.  The contents at the effective address and the X index register both remain unchanged.
+CPX assumes its operands are unsigned.
 === See Also ===
 * [[CPY]]
+* [[CMP]]
+=== External Links ===
+* [[Eyes & Lichty]] page 449, on CPX: https://archive.org/details/0893037893ProgrammingThe65816/page/n475
+* [[Labiak]] page 136 on CPX: https://archive.org/details/Programming_the_65816/page/n146
+* [[MCS6500 Manual]] page 99 on CPX: https://archive.org/details/mos_microcomputers_programming_manual/page/n117
+* [[Carr]] page 256 on CPX: https://archive.org/details/6502UsersManual/page/n269
+* [[Leventhal]] page 3-58 on CPX: https://archive.org/details/6502-assembly-language-programming/page/n107
+* snes9x implementation of CPX: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L402
+* undisbeliever on CPX: https://undisbeliever.net/snesdev/65816-opcodes.html#cpx-compare-index-register-x-with-memory
 [[Category:ASM]]
 [[Category:Group Three Instructions]]
 [[Category:Inherited from 6502]]