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ROR: Difference between revisions
From SnesLab
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!colspan="9"|Flags Affected | !colspan="9"|Flags Affected | ||
|+ | |+ | ||
|N | |[[N Flag|N]] | ||
|V | |[[V Flag|V]] | ||
|M | |[[M Flag|M]] | ||
|X | |[[X Flag|X]] | ||
|D | |[[D Flag|D]] | ||
|I | |[[I Flag|I]] | ||
|Z | |[[Z Flag|Z]] | ||
|C | |[[C Flag|C]] | ||
|+ | |+ | ||
| | | | ||
Revision as of 03:07, 27 November 2023
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Accumulator | 6A | 1 byte | 2 cycles | ||||
| Absolute | 6E | 3 bytes | 6 cycles* | ||||
| Direct Page | 66 | 2 bytes | 5 cycles* | ||||
| absolute indexed by X | 7E | 3 bytes | 7 cycles* | ||||
| direct page indexed by X | 76 | 2 bytes | 6 cycles* | ||||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| N | V | M | X | D | I | Z | C | |
| . | . | . | . | . | ||||
ROR (Rotate Right) is a 65x instruction that rotates a value and the carry flag right one bit. The least significant bit is shifted into the carry flag. The carry flag is shifted into the most significant bit.
Cycle Penalties
- Except in accumulator addressing, ROR takes two extra cycles when the accumulator is 16 bits wide.
- In direct page addressing modes, ROR takes another extra cycle if the low byte of the direct page register is nonzero.
See Also
External Links
- Eyes & Lichty page 491, on ROR: https://archive.org/details/0893037893ProgrammingThe65816/page/n517
- Labiak page on ROR: https://archive.org/details/Programming_the_65816/page/n185
- MCS6500 Manual page on ROR: https://archive.org/details/mos_microcomputers_programming_manual/page/n171
- Carr page on ROR: https://archive.org/details/6502UsersManual/page/n282
- Leventhal page on ROR: https://archive.org/details/6502-assembly-language-programming/page/n136
- snes9x implementation of ROR: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1070
- undisbeliever on ROR: https://undisbeliever.net/snesdev/65816-opcodes.html#ror-rotate-right