ASL: Difference between revisions

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

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.

External Links

Eyes & Lichty, page 427 on ASL
lbid page 190, before & after diagram of ASL
Labiak, page 117 on ASL
10.2 on MCS6500 Manual, page 149 on ASL
B-4, lbid.
Carr, page 247 on ASL
Leventhal, page 3-41 on ASL
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

@@ Line 1: / Line 1: @@
-'''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.
+{| class="wikitable" style="float:right;clear:right;width:40%"
-{| class="wikitable" style="float:right;clear:right;width:30%"
 !colspan="8"|Basic Info
 |+
@@ Line 9: / Line 7: @@
 |'''Speed'''
 |+
-|accumulator
+|[[Accumulator Addressing|Accumulator]]
 |0A
 |1 byte
 |2 cycles
 |+
-|absolute
+|[[Absolute]]
 |0E
 |3 bytes
-|6 cycles
+|6 cycles*
 |+
-|direct page
+|[[Direct Page Addressing|Direct Page]]
 |06
 |2 bytes
-|5 cycles
+|5 cycles*
 |+
-|absolute indexed X
+|[[Absolute Indexed by X]]
 |1E
 |3 bytes
-|7 cycles
+|7 cycles*
 |+
-|direct page indexed X
+|[[Direct Page Indexed by X]]
 |16
 |2 bytes
-|6 cycles
+|6 cycles*
 |}
-{| class="wikitable" style="width:30%"
+{| class="wikitable" style="float:right;clear:right;width:30%"
-!colspan="9"|Flags Clobbered
+!colspan="9"|Flags Affected
+|+
+|[[N Flag|N]]
+|[[V Flag|V]]
+|[[M Flag|M]]
+|[[X Flag|X]]
+|[[D Flag|D]]
+|[[I Flag|I]]
+|[[Z Flag|Z]]
+|[[C Flag|C]]
 |+
 |N
-|V
-|M
-|X
-|D
-|I
-|Z
-|C
-|+
-|
 |.
 |.
@@ Line 53: / Line 51: @@
 |.
 |.
-|
+|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 ====
+<pre>
+ASL
+ASL A
+ASL addr
+ASL dp
+ASL addr, X
+ASL dp, X
+</pre>
+==== Cycle Penalties ====
+* 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.
+[[File:816_asl.png]]
+=== See Also ===
+* [[LSR]]
+* [[ASL (SPC700)]]
+* [[ROL]]
+=== External Links ===
+* [[Eyes & Lichty]], [https://archive.org/details/0893037893ProgrammingThe65816/page/427 page 427] on ASL
+* lbid [https://archive.org/details/0893037893ProgrammingThe65816/page/190 page 190], before & after diagram of ASL
+* [[Labiak]], [https://archive.org/details/Programming_the_65816/page/n127 page 117] on ASL
+* 10.2 on [[MCS6500 Manual]], [https://archive.org/details/mos_microcomputers_programming_manual/page/n170 page 149] on ASL
+* [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
+* Pickens, John. http://www.6502.org/tutorials/6502opcodes.html#ASL
+* Clark, Bruce. http://www.6502.org/tutorials/65c816opcodes.html#6.1.3
 [[Category:ASM]]