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LSR (SPC700): Difference between revisions
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!colspan="8"|Basic Info | !colspan="8"|Basic Info | ||
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|'''Speed''' | |'''Speed''' | ||
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| | |[[Accumulator Addressing | Accumulator]] | ||
|5C | |5C | ||
|1 byte | |1 byte | ||
|2 cycles | |2 cycles | ||
|+ | |+ | ||
| | |[[Direct Page Addressing | Direct Page]] | ||
|4B | |4B | ||
|2 bytes | |2 bytes | ||
|4 cycles | |4 cycles | ||
|+ | |+ | ||
| | |[[Direct Page Indexed by X]] | ||
|5B | |5B | ||
|2 bytes | |2 bytes | ||
|5 cycles | |5 cycles | ||
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| | |[[Absolute Addressing | Absolute]] | ||
|4C | |4C | ||
|3 bytes | |3 bytes | ||
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!colspan="8"|Flags | !colspan="8"|Flags Affected | ||
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|[[Negative Flag|N]] | |||
|[[Overflow Flag|V]] | |||
|[[Direct Page Flag|P]] | |||
|[[Break Flag|B]] | |||
|[[Half-Carry Flag|H]] | |||
|[[Interrupt Enable Flag|I]] | |||
|[[Zero Flag|Z]] | |||
|[[Carry Flag|C]] | |||
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|N | |N | ||
|. | |. | ||
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'''LSR''' (Logical Shift Right) is an [[SPC700]] instruction that shifts all 8 bits of its operand one bit to the right, dividing it by two. The least significant bit is shifted into the [[carry flag]]. A zero is shifted into the most significant bit. | |||
The official manual has the bit shift operators for LSR pointing the wrong way. | |||
==== Syntax ==== | |||
<pre> | |||
LSR A | |||
LSR dp | |||
LSR dp+X | |||
LSR !abs | |||
</pre> | |||
[[File:lsr_spc.png]] | |||
LSR is a fast alternative to [[DIV]] when dividing by a power of two. | |||
=== See Also === | |||
* [[ASL (SPC700)]] | |||
* [[LSR]] | |||
=== External Links === | === External Links === | ||
* Official Nintendo | * Official Super Nintendo development manual on LSR: [https://archive.org/details/SNESDevManual/book1/page/n232 Appendix C-7 of Book I] | ||
* anomie: https://github.com/yupferris/TasmShiz/blob/master/spc700.txt#L457 | |||
[[Category:ASM]] | [[Category:ASM]] | ||
[[Category:SPC700]] | [[Category:SPC700]] | ||
[[Category:Shift Rotation Commands]] | [[Category:Shift Rotation Commands]] | ||
Latest revision as of 00:04, 15 August 2024
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Accumulator | 5C | 1 byte | 2 cycles | ||||
| Direct Page | 4B | 2 bytes | 4 cycles | ||||
| Direct Page Indexed by X | 5B | 2 bytes | 5 cycles | ||||
| Absolute | 4C | 3 bytes | 5 cycles | ||||
| Flags Affected | |||||||
|---|---|---|---|---|---|---|---|
| N | V | P | B | H | I | Z | C |
| N | . | . | . | . | . | Z | C |
LSR (Logical Shift Right) is an SPC700 instruction that shifts all 8 bits of its operand one bit to the right, dividing it by two. The least significant bit is shifted into the carry flag. A zero is shifted into the most significant bit.
The official manual has the bit shift operators for LSR pointing the wrong way.
Syntax
LSR A LSR dp LSR dp+X LSR !abs
LSR is a fast alternative to DIV when dividing by a power of two.
See Also
External Links
- Official Super Nintendo development manual on LSR: Appendix C-7 of Book I
- anomie: https://github.com/yupferris/TasmShiz/blob/master/spc700.txt#L457