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ASL: Difference between revisions
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'''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 | '''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). | The size of the accumulator determines how many bits are shifted (8 or 16) not including the clearing zero and carry flag. | ||
==== Syntax ==== | ==== Syntax ==== | ||
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</pre> | </pre> | ||
==== 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. | ||
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* [[Labiak]], [https://archive.org/details/Programming_the_65816/page/n127 page 117] on 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 | * 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 | * [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 | * [[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 | * [[Leventhal]], [https://archive.org/details/6502-assembly-language-programming/page/n90 page 3-41] on ASL | ||
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.
See Also
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