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ASL: Difference between revisions
From SnesLab
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!colspan="9"|Flags Affected | !colspan="9"|Flags Affected | ||
|+ | |+ | ||
|N | |[[N Flag|N]] | ||
|V | |[[V Flag|V]] | ||
|M | |[[M Flag|M]] | ||
|X | |[[X Flag|X]] | ||
|D | |[[D Flag|D]] | ||
|I | |[[I Flag|I]] | ||
|Z | |[[Z Flag|Z]] | ||
|C | |[[C Flag|C]] | ||
|+ | |+ | ||
| | | | ||
Revision as of 03:07, 27 November 2023
| 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 X | 1E | 3 bytes | 7 cycles* | ||||
| direct page indexed 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
- Labiak page on ASL: https://archive.org/details/Programming_the_65816/page/n127
- MCS6500 Manual page on ASL: https://archive.org/details/mos_microcomputers_programming_manual/page/n170
- Carr page on ASL: https://archive.org/details/6502UsersManual/page/n260
- Leventhal page 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