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INC: Difference between revisions
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'''INC''' (Increment) is a 65x instruction that increments the value in the location specified by the operand. The size of the [[accumulator]] determines whether this is an 8 or 16 bit operation. An alternate mnemonic is "INA." | '''INC''' (Increment) is a 65x instruction that increments the value in the location specified by the operand. The size of the [[accumulator]] determines whether this is an 8 or 16 bit operation. An alternate mnemonic when the operand is the accumulator is "INA." | ||
INC ignores the [[decimal mode flag]]. | INC ignores the [[decimal mode flag]]. | ||
Revision as of 20:57, 6 July 2024
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Accumulator | 1A | 1 byte | 2 cycles | ||||
| Absolute | EE | 3 bytes | 6 cycles* | ||||
| Direct Page | E6 | 2 bytes | 5 cycles* | ||||
| Absolute Indexed by X | FE | 3 bytes | 7 cycles* | ||||
| Direct Page Indexed by X | F6 | 2 bytes | 6 cycles* | ||||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| N | V | M | X | D | I | Z | C | |
| . | . | . | . | . | . | |||
INC (Increment) is a 65x instruction that increments the value in the location specified by the operand. The size of the accumulator determines whether this is an 8 or 16 bit operation. An alternate mnemonic when the operand is the accumulator is "INA."
INC ignores the decimal mode flag.
Cycle Penalties
- Except in accumulator addressing, INC takes two extra cycles when the accumulator is 16 bits wide.
- In direct page addressing modes, INC takes an extra cycle if the low byte of the direct page register is nonzero.
See Also
External Links
- Eyes & Lichty page 456, on INC: https://archive.org/details/0893037893ProgrammingThe65816/page/n482
- Labiak page 142 on INC: https://archive.org/details/Programming_the_65816/page/n152
- MCS6500 Manual page 155 on INC: https://archive.org/details/mos_microcomputers_programming_manual/page/n176
- Carr page 260 on INC: https://archive.org/details/6502UsersManual/page/n273
- Leventhal page 3-65 on INC: https://archive.org/details/6502-assembly-language-programming/page/n114
- snes9x implementation of INC: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L627
- undisbeliever on INC: https://undisbeliever.net/snesdev/65816-opcodes.html#inc-increment