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ROL: Difference between revisions

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===== Cycle Penalties =====
==== Cycle Penalties ====
* Except in [[accumulator addressing]], ROL takes two extra cycles when the accumulator is 16 bits wide.
* Except in [[accumulator addressing]], ROL takes two extra cycles when the accumulator is 16 bits wide.
* In [[direct page addressing]] modes, ROL takes another extra cycle if the low byte of the [[direct page register]] is nonzero.
* In [[direct page addressing]] modes, ROL takes another extra cycle if the low byte of the [[direct page register]] is nonzero.

Latest revision as of 17:44, 23 August 2024

Basic Info
Addressing Mode Opcode Length Speed
Accumulator 2A 1 byte 2 cycles
Absolute 2E 3 bytes 6 cycles*
Direct Page 26 2 bytes 5 cycles*
Absolute Indexed by X 3E 3 bytes 7 cycles*
Direct Page Indexed by X 36 2 bytes 6 cycles*
Flags Affected
N V M X D I Z C
N . . . . . Z C

ROL (Rotate Left) is a 65x instruction that rotates a value and the carry flag left one bit. The most significant bit is shifted into the carry flag. The carry flag is shifted into the least significant bit.

  • When the accumulator is 8 bits wide, 9 bits are rotated.
  • When the accumulator is 16 bits wide, 17 bits are rotated.

Syntax

ROL
ROL A
ROL addr
ROL dp
ROL addr, X
ROL dp, X

Cycle Penalties

816 rol.png

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See Also

External Links