BRK: Difference between revisions

Revision as of 07:37, 26 November 2023


Basic Info
Addressing Mode	Opcode	Length	Speed
Stack	00	2 bytes	8 cycles*


Flags Affected
	N	V	M	X / B	D	I	Z	C
65c816 native mode	.	.	.	.	0	1	.	.
6502 emulation mode	.	.	.	1	0	1	.	.

BRK (Break) is a 65x instruction designed to trigger a software interrupt. The byte following the opcode is called the Signature Byte. The state of the interrupt disable flag has no effect on the behavior of BRK.

Cycle Skipped

BRK 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 436, on BRK: https://archive.org/details/0893037893ProgrammingThe65816/page/n462
Labiak page on BRK: https://archive.org/details/Programming_the_65816/page/n136
MCS6500 Manual page on BRK: https://archive.org/details/mos_microcomputers_programming_manual/page/n164
Carr page on BRK: https://archive.org/details/6502UsersManual/page/n265
Leventhal page on BRK: https://archive.org/details/6502-assembly-language-programming/page/n98
snes9x implementation of BRK: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L2547

@@ Line 10: / Line 10: @@
 |00
 |2 bytes
-|7 cycles*
+|8 cycles*
 |}
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 '''BRK''' (Break) is a 65x instruction designed to trigger a software interrupt.  The byte following the opcode is called the [[Signature Byte]].  The state of the [[interrupt disable flag]] has no effect on the behavior of BRK.
-===== Cycle Penalty =====
+===== Cycle Skipped =====
-BRK takes one extra cycle in [[native mode]] as it needs to push the [[program counter bank register]] to the [[stack]].
+BRK takes one fewer cycle in [[emulation mode]] as it doesn't need to push the [[program counter bank register]] to the [[stack]].
 === See Also ===