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ASL: Difference between revisions
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* 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:asl.png]] | |||
=== See Also === | === See Also === | ||
Revision as of 18:22, 27 June 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 becomes a zero.
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/n453
- 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