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BRA: Difference between revisions
From SnesLab
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BRA has the same timing as other branches, it just has no "branch not taken" case. | |||
===== Cycle Penalty ===== | ===== Cycle Penalty ===== | ||
Revision as of 21:41, 22 July 2024
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Program Counter Relative | 80 | 2 bytes | 3 cycles* | ||||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| N | V | M | X | D | I | Z | C | |
| . | . | . | . | . | . | . | . | |
BRA (BRanch Always) is a 65c816 instruction that performs an unconditional jump. The signed displacement ranges from -128 to 127. The displacement is sign-extended to 16 bits and added to the program counter.
BRA is relocatable. No flags are affected.
Syntax
BRA nearlabel
BRA has the same timing as other branches, it just has no "branch not taken" case.
Cycle Penalty
- BRA takes one additional cycle if the branch crosses a page boundary in emulation mode.
See Also
External Links
- Eyes & Lichty page 435, on BRA: https://archive.org/details/0893037893ProgrammingThe65816/page/435
- Labiak page 125 on BRA: https://archive.org/details/Programming_the_65816/page/n135
- snes9x implementation of BRA: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1390
- Clark, Bruce. http://www.6502.org/tutorials/65c816opcodes.html#6.2.1.1