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BPL: Difference between revisions
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!colspan="9"|Flags Affected | !colspan="9"|Flags Affected | ||
|+ | |+ | ||
|N | |[[Negative Flag|N]] | ||
|V | |[[Overflow Flag|V]] | ||
|M | |[[M Flag|M]] | ||
|X | |[[X Flag|X]] | ||
|D | |[[Decimal Flag|D]] | ||
|I | |[[I Flag|I]] | ||
|Z | |[[Zero Flag|Z]] | ||
|C | |[[Carry Flag|C]] | ||
|+ | |+ | ||
|. | |. | ||
Revision as of 04:07, 27 November 2023
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Program Counter Relative | 10 | 2 byte | 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.
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 on BPL: https://archive.org/details/0893037893ProgrammingThe65816/page/n460
- Labiak page on BPL: https://archive.org/details/Programming_the_65816/page/n133
- MCS6500 Manual page on BPL: https://archive.org/details/mos_microcomputers_programming_manual/page/n55
- Carr page on BPL: https://archive.org/details/6502UsersManual/page/n264
- Leventhal page on BPL: https://archive.org/details/6502-assembly-language-programming/page/n97
- snes9x implementation of BPL: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1385