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LSR (SPC700)
From SnesLab
| 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