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BMI: Difference between revisions
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'''BMI''' (Branch if Minus) is a 65x instruction that performs a jump if the [[negative flag]] is set. The signed displacement of the target address can range from -128 to 127. | '''BMI''' (Branch if Minus) is a 65x instruction that performs a jump if the [[negative flag]] is set. The signed displacement of the target address can range from -128 to 127. | ||
If the negative flag is clear, control simply falls through to the instruction following BMI. | |||
No flags are affected. | No flags are affected. | ||
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</pre> | </pre> | ||
==== Cycle Penalties ==== | |||
* BMI takes one extra cycle if the branch is taken | * BMI takes one extra cycle if the branch is taken | ||
* BMI takes another extra cycle if that branch crosses a page boundary in [[emulation mode]]. | * BMI takes another extra cycle if that branch crosses a page boundary in [[emulation mode]]. | ||
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* 4.1.2.1 on [[MCS6500 Manual]], [https://archive.org/details/mos_microcomputers_programming_manual/page/n55 page 40] on BMI | * 4.1.2.1 on [[MCS6500 Manual]], [https://archive.org/details/mos_microcomputers_programming_manual/page/n55 page 40] on BMI | ||
* [[Carr]], [https://archive.org/details/6502UsersManual/page/n263 page 250] on BMI | * [[Carr]], [https://archive.org/details/6502UsersManual/page/n263 page 250] on BMI | ||
* [[Leventhal]] | * [[Leventhal]], [https://archive.org/details/6502-assembly-language-programming/page/n96 page 3-47] on BMI | ||
* snes9x implementation of BMI: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1375 | * snes9x implementation of BMI: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1375 | ||
Latest revision as of 06:59, 22 August 2024
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Program Counter Relative | 30 | 2 bytes | 2 cycles* | ||||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| N | V | M | X | D | I | Z | C | |
| . | . | . | . | . | . | . | . | |
BMI (Branch if Minus) is a 65x instruction that performs a jump if the negative flag is set. The signed displacement of the target address can range from -128 to 127.
If the negative flag is clear, control simply falls through to the instruction following BMI.
No flags are affected.
Syntax
BMI nearlabel
Cycle Penalties
- BMI takes one extra cycle if the branch is taken
- BMI takes another extra cycle if that branch crosses a page boundary in emulation mode.
See Also
External Links
- Eyes & Lichty, page 432 on BMI
- Labiak, page 122 on BMI
- 4.1.2.1 on MCS6500 Manual, page 40 on BMI
- Carr, page 250 on BMI
- Leventhal, page 3-47 on BMI
- snes9x implementation of BMI: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1375