COP: Difference between revisions

Revision as of 06:06, 26 November 2023


Basic Info
Addressing Mode	Opcode	Length	Speed
Stack	02	2 bytes	8 cycles*


Flags Affected
N	V	M	X	D	I	Z	C
.	.	.	.	0	1	.	.

COP (Co-Processor) is a 65c816 instruction designed to run a co-processor command. The byte following the opcode is called the Signature Byte. Signature bytes of 80h to FFh are reserved by the Western Design Center. The state of the interrupt disable flag has no effect on the behavior of COP.

Cycle Skipped

COP takes one fewer cycle in emulation mode as it doesn't need to push the program counter bank register to the stack.

External Links

Eyes & Lichty page 447, on COP: https://archive.org/details/0893037893ProgrammingThe65816/page/n473
Labiak page on COP: https://archive.org/details/Programming_the_65816/page/n145
snes9x implementation of COP: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L2738

@@ Line 10: / Line 10: @@
 |02
 |2 bytes
-|7 cycles*
+|8 cycles*
 |}
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 '''COP''' (Co-Processor) is a [[65c816]] instruction designed to run a co-processor command.  The byte following the opcode is called the [[Signature Byte]].  Signature bytes of 80h to FFh are reserved by the Western Design Center.  The state of the [[interrupt disable flag]] has no effect on the behavior of COP.
-=====Cycle Penalty =====
+=====Cycle Skipped =====
-* COP takes one extra cycle in [[native mode]] as it needs to push the [[program counter bank register]] to the [[stack]].
+* COP takes one fewer cycle in [[emulation mode]] as it doesn't need to push the [[program counter bank register]] to the [[stack]].
 === See Also ===