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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 every bit 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