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'''ASL''' (Arithmetic Shift Left) is a 65x instruction that shifts a value by left one bit (multiplication by two).  The most significant bit is shifted into the [[carry flag]].  The least significant bit becomes a zero.
'''ASL''' (Arithmetic Shift Left) is a 65x instruction that shifts every bit of a value left one bit (multiplication by two).  The least significant bit is cleared.  The most significant bit is shifted into the [[carry flag]].  The previous value of the carry flag is lost (unlike with [[ROL]]).
 
The size of the accumulator determines how many bits are shifted (8 or 16) not including the clearing zero and carry flag.
 
==== Syntax ====
<pre>
ASL
ASL A
ASL addr
ASL dp
ASL addr, X
ASL dp, X
</pre>


===== Cycle Penalties =====
==== Cycle Penalties ====
* Except in [[accumulator addressing]], ASL takes two extra cycles when the accumulator is 16 bits wide
* Except in [[accumulator addressing]], ASL takes two extra cycles when the accumulator is 16 bits wide
* In [[direct page addressing]] modes, ASL takes another extra cycle if the low byte of the [[direct page register]] is nonzero.
* In [[direct page addressing]] modes, ASL takes another extra cycle if the low byte of the [[direct page register]] is nonzero.
[[File:816_asl.png]]


=== See Also ===
=== See Also ===
* [[LSR]]
* [[LSR]]
* [[ASL (SPC700)]]
* [[ASL (SPC700)]]
* [[ROL]]


=== External Links ===
=== External Links ===
* [[Eyes & Lichty]] page 427, on ASL: https://archive.org/details/0893037893ProgrammingThe65816/page/n453
* [[Eyes & Lichty]], [https://archive.org/details/0893037893ProgrammingThe65816/page/427 page 427] on ASL
* [[Labiak]] page on ASL: https://archive.org/details/Programming_the_65816/page/n127
* lbid [https://archive.org/details/0893037893ProgrammingThe65816/page/190 page 190], before & after diagram of ASL
* [[MCS6500 Manual]] page on ASL: https://archive.org/details/mos_microcomputers_programming_manual/page/n170
* [[Labiak]], [https://archive.org/details/Programming_the_65816/page/n127 page 117] on ASL
* [[Carr]] page on ASL: https://archive.org/details/6502UsersManual/page/n260
* 10.2 on [[MCS6500 Manual]], [https://archive.org/details/mos_microcomputers_programming_manual/page/n170 page 149] on ASL
* [[Leventhal]] page on ASL: https://archive.org/details/6502-assembly-language-programming/page/n90
* [https://archive.org/details/mos_microcomputers_programming_manual/page/n205 B-4], lbid.
* [[Carr]], [https://archive.org/details/6502UsersManual/page/n260 page 247] on ASL
* [[Leventhal]], [https://archive.org/details/6502-assembly-language-programming/page/n90 page 3-41] on ASL
* undisbeliever on ASL: https://undisbeliever.net/snesdev/65816-opcodes.html#asl-arithmetic-shift-left
* undisbeliever on ASL: https://undisbeliever.net/snesdev/65816-opcodes.html#asl-arithmetic-shift-left
* Pickens, John. http://www.6502.org/tutorials/6502opcodes.html#ASL
* Clark, Bruce. http://www.6502.org/tutorials/65c816opcodes.html#6.1.3


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

Latest revision as of 17:45, 23 August 2024

Basic Info
Addressing Mode Opcode Length Speed
Accumulator 0A 1 byte 2 cycles
Absolute 0E 3 bytes 6 cycles*
Direct Page 06 2 bytes 5 cycles*
Absolute Indexed by X 1E 3 bytes 7 cycles*
Direct Page Indexed by X 16 2 bytes 6 cycles*
Flags Affected
N V M X D I Z C
N . . . . . Z C

ASL (Arithmetic Shift Left) is a 65x instruction that shifts every bit of a value left one bit (multiplication by two). The least significant bit is cleared. The most significant bit is shifted into the carry flag. The previous value of the carry flag is lost (unlike with ROL).

The size of the accumulator determines how many bits are shifted (8 or 16) not including the clearing zero and carry flag.

Syntax

ASL
ASL A
ASL addr
ASL dp
ASL addr, X
ASL dp, X

Cycle Penalties

816 asl.png

See Also

External Links