We've just updated MediaWiki and its underlying software. If anything doesn't look or work quite right, please mention it to us. --RanAS
BPL: Difference between revisions
From SnesLab
(additional cycles) |
(→External Links: MCS page) |
||
| (12 intermediate revisions by the same user not shown) | |||
| Line 7: | Line 7: | ||
|'''Speed''' | |'''Speed''' | ||
|+ | |+ | ||
| | |[[Program Counter Relative]] | ||
|10 | |10 | ||
|2 byte | |2 byte | ||
| Line 16: | Line 16: | ||
!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]] | ||
|+ | |+ | ||
|. | |. | ||
| Line 35: | Line 35: | ||
|} | |} | ||
'''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." | '''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 === | === See Also === | ||
* [[BMI]] | |||
* [[BNE]] | * [[BNE]] | ||
* [[BPL (SPC700)]] | * [[BPL (SPC700)]] | ||
| Line 43: | Line 50: | ||
=== External Links === | === External Links === | ||
* [[Eyes & Lichty]] page on BPL: https://archive.org/details/0893037893ProgrammingThe65816/page/n460 | * [[Eyes & Lichty]] page 434 on BPL: https://archive.org/details/0893037893ProgrammingThe65816/page/n460 | ||
* [[Labiak]] page on BPL: https://archive.org/details/Programming_the_65816/page/ | * [[Labiak]] page 124 on BPL: https://archive.org/details/Programming_the_65816/page/n134 | ||
* [[MCS6500 Manual]] page on BPL: https://archive.org/details/mos_microcomputers_programming_manual/page/n55 | * [[MCS6500 Manual]] page 40 on BPL: https://archive.org/details/mos_microcomputers_programming_manual/page/n55 | ||
* [[Carr]] page on BPL: https://archive.org/details/6502UsersManual/page/n264 | * [[Carr]] page 251 on BPL: https://archive.org/details/6502UsersManual/page/n264 | ||
* [[Leventhal]] page on BPL: https://archive.org/details/6502-assembly-language-programming/page/n97 | * [[Leventhal]] page 3-48 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 | * snes9x implementation of BPL: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1385 | ||
[[Category:ASM]] | [[Category:ASM]] | ||
[[Category:Inherited from 6502]] | [[Category:Inherited from 6502]] | ||
[[Category:Conditional Branches]] | |||
[[Category:Two-byte Instructions]] | |||
Latest revision as of 04:16, 6 December 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 434 on BPL: https://archive.org/details/0893037893ProgrammingThe65816/page/n460
- Labiak page 124 on BPL: https://archive.org/details/Programming_the_65816/page/n134
- MCS6500 Manual page 40 on BPL: https://archive.org/details/mos_microcomputers_programming_manual/page/n55
- Carr page 251 on BPL: https://archive.org/details/6502UsersManual/page/n264
- Leventhal page 3-48 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