ROL

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. If not using accumulator addressing, the low-order byte is located at the effective address and the high-order byte at the effective address plus one.

Syntax

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

Cycle Penalties

• Except in accumulator addressing, ROL takes two extra cycles when the accumulator is 16 bits wide.
• In direct page addressing modes (opcodes 26 and 36), ROL takes another extra cycle if the low byte of the direct page register is nonzero.

The arrow in the Carr textbook diagram does not circle back around.

See Also

• ROR
• ASL
• ROL (SPC700)
• ROL (Super FX)

External Links

• Eyes & Lichty, page 490 on ROL
• lbid page 190 before & after diagram of ROL
• Labiak, page 174 on ROL
• 10.3 on MCS6500 Manual, page 149 on ROL
• Carr, page 269 on ROL
• Leventhal, page 3-85 on ROL
• snes9x implementation of ROL: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1011
• undisbeliever on ROL: https://undisbeliever.net/snesdev/65816-opcodes.html#rol-rotate-left
• Pickens, John. http://www.6502.org/tutorials/6502opcodes.html#ROL
• Clark, Bruce. http://www.6502.org/tutorials/65c816opcodes.html#6.1.3