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BPL
From SnesLab
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Program Counter Relative | 10 | 2 bytes | 2 cycles* | ||||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| N | V | M | X | D | I | Z | C | |
| . | . | . | . | . | . | . | . | |
BPL (Branch if PLus) is a 65x instruction that performs a jump if the negative flag is clear. Note that zero is considered positive in the 65x architecture, so this instruction's behavior might be more accurately be described as "branch if non-negative."
The signed displacement of the target address can range from -128 to 127.
If the negative flag is set, control simply falls through to the instruction following BPL.
No flags are affected.
Syntax
BPL nearlabel
Cycle Penalties
- BPL takes one additional cycle if the branch is taken
- BPL takes another extra cycle if that branch taken crosses a page boundary in emulation mode.
See Also
External Links
- Eyes & Lichty, page 434 on BPL
- Labiak, page 124 on BPL
- 4.1.2.2 on MCS6500 Manual, page 40 on BPL
- Carr, page 251 on BPL
- Leventhal, page 3-48 on BPL
- snes9x implementation of BPL: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1385