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BMI: Difference between revisions
From SnesLab
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|'''Speed''' | |'''Speed''' | ||
|+ | |+ | ||
| | |[[Program Counter Relative]] | ||
|30 | |30 | ||
|2 | |2 bytes | ||
|2 cycles | |2 cycles* | ||
|} | |} | ||
{| class="wikitable" style="float:right;clear:right;width:30%" | {| class="wikitable" style="float:right;clear:right;width:30%" | ||
!colspan="9"|Flags | !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: | ||
|} | |} | ||
'''BMI''' (Branch if Minus) is a 65x instruction that performs a jump if the [[negative flag]] is set. | '''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 ==== | |||
<pre> | |||
BMI nearlabel | |||
</pre> | |||
==== 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 === | === See Also === | ||
| Line 42: | Line 55: | ||
=== External Links === | === External Links === | ||
* [[Eyes & Lichty]] | * [[Eyes & Lichty]], [https://archive.org/details/0893037893ProgrammingThe65816/page/432 page 432] on BMI | ||
* [[Labiak]] | * [[Labiak]], [https://archive.org/details/Programming_the_65816/page/n132 page 122] on BMI | ||
* [[MCS6500 Manual]] | * 4.1.2.1 on [[MCS6500 Manual]], [https://archive.org/details/mos_microcomputers_programming_manual/page/n55 page 40] on BMI | ||
* [[Carr]] | * [[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 | ||
[[Category:ASM]] | [[Category:ASM]] | ||
[[Category:Inherited from 6502]] | [[Category:Inherited from 6502]] | ||
[[Category:Conditional Branches]] | |||
[[Category:Two-byte Instructions]] | |||
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