CPY: Difference between revisions

Latest revision as of 07:51, 19 December 2023


Basic Info
Addressing Mode	Opcode	Length	Speed
Immediate	C0	2 bytes*	2 cycles*
Absolute	CC	3 bytes	4 cycles*
Direct Page	C4	2 bytes	3 cycles*


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

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

CPY assumes its operands are unsigned.

External Links

Eyes & Lichty page 450, on CPY: https://archive.org/details/0893037893ProgrammingThe65816/page/n476
Labiak page 137 on CPY: https://archive.org/details/Programming_the_65816/page/n147
MCS6500 Manual page 99 on CPY: https://archive.org/details/mos_microcomputers_programming_manual/page/n117
Carr page 257 on CPY: https://archive.org/details/6502UsersManual/page/n270
Leventhal page 3-59 on CPY: https://archive.org/details/6502-assembly-language-programming/page/n108
snes9x implementation of CPY: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L442
undisbeliever on CPY: https://undisbeliever.net/snesdev/65816-opcodes.html#cpy-compare-index-register-y-with-memory

@@ Line 1: / Line 1: @@
-'''CPY''' (Compare Y) is a 65x instruction that compares the value of the [[Y index register]].
+{| class="wikitable" style="float:right;clear:right;width:40%"
+!colspan="8"|Basic Info
+|+
+|'''Addressing Mode'''
+|'''Opcode'''
+|'''Length'''
+|'''Speed'''
+|+
+|[[Immediate]]
+|C0
+|2 bytes*
+|2 cycles*
+|+
+|[[Absolute]]
+|CC
+|3 bytes
+|4 cycles*
+|+
+|[[Direct Page Addressing|Direct Page]]
+|C4
+|2 bytes
+|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 22: / Line 44: @@
 |
 |}
+'''CPY''' (Compare Y) is a 65x instruction that compares the value of the [[Y index register]].  Internally, this is done via a subtraction, but the difference is not stored anywhere.  The contents at the effective address and the Y index register both remain unchanged.
+CPY assumes its operands are unsigned.
 === See Also ===
 * [[CPX]]
+* [[CMP]]
+=== External Links ===
+* [[Eyes & Lichty]] page 450, on CPY: https://archive.org/details/0893037893ProgrammingThe65816/page/n476
+* [[Labiak]] page 137 on CPY: https://archive.org/details/Programming_the_65816/page/n147
+* [[MCS6500 Manual]] page 99 on CPY: https://archive.org/details/mos_microcomputers_programming_manual/page/n117
+* [[Carr]] page 257 on CPY: https://archive.org/details/6502UsersManual/page/n270
+* [[Leventhal]] page 3-59 on CPY: https://archive.org/details/6502-assembly-language-programming/page/n108
+* snes9x implementation of CPY: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L442
+* undisbeliever on CPY: https://undisbeliever.net/snesdev/65816-opcodes.html#cpy-compare-index-register-y-with-memory
 [[Category:ASM]]
+[[Category:Group Three Instructions]]
+[[Category:Inherited from 6502]]