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ASL: Difference between revisions
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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 is cleared. | '''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 is cleared. | ||
The size of the accumulator determines how many bits are shifted (8 or 16). | |||
==== Syntax ==== | ==== Syntax ==== | ||
Revision as of 12:42, 22 July 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 | |
| . | . | . | . | . | ||||
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 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.
See Also
External Links
- Eyes & Lichty page 427, on ASL: https://archive.org/details/0893037893ProgrammingThe65816/page/427
- lbid page 190, before & after diagram of ASL: https://archive.org/details/0893037893ProgrammingThe65816/page/n216
- Labiak page 117 on ASL: https://archive.org/details/Programming_the_65816/page/n127
- 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: https://archive.org/details/6502UsersManual/page/n260
- 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
- http://www.6502.org/tutorials/6502opcodes.html#ASL