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'''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.   
'''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.   


===== Cycle Penalties =====
* When the [[accumulator]] is 8 bits wide, 9 bits are rotated.
* When the accumulator is 16 bits wide, 17 bits are rotated.
 
==== Syntax ====
<pre>
ROL
ROL A
ROL addr
ROL dp
ROL addr, X
ROL dp, X
</pre>
 
==== 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.


[[File:rol.png]]
[[File:816_rol.png]]
 
The arrow in the Carr textbook diagram does not circle back around.


=== See Also ===
=== See Also ===
* [[ROR]]
* [[ROR]]
* [[ASL]]
* [[ROL (SPC700)]]
* [[ROL (SPC700)]]
* [[ROL (Super FX)]]
* [[ROL (Super FX)]]


=== External Links ===
=== External Links ===
* [[Eyes & Lichty]] page 490, on ROL: https://archive.org/details/0893037893ProgrammingThe65816/page/n516
* [[Eyes & Lichty]], [https://archive.org/details/0893037893ProgrammingThe65816/page/490 page 490] on ROL
* lbid page 190 before & after diagram of ROL: https://archive.org/details/0893037893ProgrammingThe65816/page/n216
* lbid [https://archive.org/details/0893037893ProgrammingThe65816/page/190 page 190] before & after diagram of ROL
* [[Labiak]] page 174 on ROL: https://archive.org/details/Programming_the_65816/page/n184
* [[Labiak]], [https://archive.org/details/Programming_the_65816/page/n184 page 174] on ROL
* [[MCS6500 Manual]] page 149 on ROL: https://archive.org/details/mos_microcomputers_programming_manual/page/n170
* 10.3 on [[MCS6500 Manual]], [https://archive.org/details/mos_microcomputers_programming_manual/page/n170 page 149] on ROL
* [[Carr]] page 269 on ROL: https://archive.org/details/6502UsersManual/page/n282
* [[Carr]], [https://archive.org/details/6502UsersManual/page/n282 page 269] on ROL
* [[Leventhal]] page 3-85 on ROL: https://archive.org/details/6502-assembly-language-programming/page/n134
* [[Leventhal]], [https://archive.org/details/6502-assembly-language-programming/page/n134 page 3-85] on ROL
* snes9x implementation of ROL: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1011
* 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
* 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


[[Category:ASM]]
[[Category:ASM]]

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

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

See Also

External Links