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PLA: Difference between revisions
From SnesLab
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The Eyes & Lichty page on PLA has a typo that says the 65x pull instructions "set" the zero and negative flags; it should say "affect." | The Eyes & Lichty page on PLA has a typo that says the 65x pull instructions "set" the zero and negative flags; it should say "affect." | ||
The [[negative flag]] will then match the most significant bit of the pulled value. The [[zero flag]] will indicate whether the pulled value is zero. | |||
===== Cycle Penalty ===== | ===== Cycle Penalty ===== | ||
Revision as of 21:50, 27 June 2024
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Stack (Pull) | 68 | 1 byte | 4 cycles* | ||||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| N | V | M | X | D | I | Z | C | |
| . | . | . | . | . | . | |||
PLA (PulL Accumulator) is a 65x instruction that pulls the value at the top of the stack into the accumulator. PLA increments the stack pointer before the pull. If the accumulator is 16 bits wide, the low byte is pulled and then the high byte is pulled.
The Eyes & Lichty page on PLA has a typo that says the 65x pull instructions "set" the zero and negative flags; it should say "affect."
The negative flag will then match the most significant bit of the pulled value. The zero flag will indicate whether the pulled value is zero.
Cycle Penalty
- PLA takes one extra cycle if the accumulator is 16 bits wide.
See Also
External Links
- Eyes & Lichty page 483, on PLA: https://archive.org/details/0893037893ProgrammingThe65816/page/n509
- Labiak page 167 on PLA: https://archive.org/details/Programming_the_65816/page/n177
- MCS6500 Manual page 118 on PLA: https://archive.org/details/mos_microcomputers_programming_manual/page/n137
- Carr page 268 on PLA: https://archive.org/details/6502UsersManual/page/n281
- Leventhal page 3-83 on PLA: https://archive.org/details/6502-assembly-language-programming/page/n132
- snes9x implementation of https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1982