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BRK

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Basic Info
Addressing Mode Opcode Length Speed
Stack (Interrupt) 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. In other words, BRK causes an NMI.

Control is routed to the BRK handler, whose address is stored at the BRK vector. In native mode, this vector is at $00:FFE6. In emulation mode, this vector is at $FFFE.

Syntax

BRK
BRK sig
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.

See Also

External Links