ASL: Difference between revisions

Revision as of 15:39, 7 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 most significant bit is shifted into the carry flag. The least significant bit is cleared.

The size of the accumulator determines how many bits are shifted (8 or 16).

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
MCS6500 Manual page 149 on ASL: https://archive.org/details/mos_microcomputers_programming_manual/page/n170
https://archive.org/details/mos_microcomputers_programming_manual/page/n205
Carr, page 247 on ASL
Leventhal page 3-41 on ASL: https://archive.org/details/6502-assembly-language-programming/page/n90
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 73: / Line 73: @@
 * In [[direct page addressing]] modes, ASL takes another extra cycle if the low byte of the [[direct page register]] is nonzero.
-[[File:asl_816.png]]
+[[File:816_asl.png]]
 === See Also ===