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WAI: Difference between revisions
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'''WAI''' (WAit for Interrupt) is a 65x instruction that waits until an interrupt is received. The processor consumes less power while waiting. The [[RDY pin]] is pulled low during the third cycle. The interrupt is serviced immediately. | '''WAI''' (WAit for Interrupt) is a 65x instruction that waits until an interrupt is received. The processor consumes less power while waiting. The [[RDY pin]] is pulled low during the third cycle and the bus is freed up. The interrupt is serviced immediately. | ||
If the [[interrupt disable flag]] is set, then the way servicing occurs is for control to simply fall through to the instruction following WAI. | If the [[interrupt disable flag]] is set, then the way servicing occurs is for control to simply fall through to the instruction following WAI. | ||
Revision as of 14:03, 14 December 2023
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Implied (type 3) | CB | 1 byte | 3 cycles | ||||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| N | V | M | X | D | I | Z | C | |
| . | . | . | . | . | . | . | . | |
WAI (WAit for Interrupt) is a 65x instruction that waits until an interrupt is received. The processor consumes less power while waiting. The RDY pin is pulled low during the third cycle and the bus is freed up. The interrupt is serviced immediately.
If the interrupt disable flag is set, then the way servicing occurs is for control to simply fall through to the instruction following WAI.
If that flag clear, control instead goes into the interrupt handler.
See Also
External Links
- Eyes & Lichty page 522, on WAI: https://archive.org/details/0893037893ProgrammingThe65816/page/n548
- Labiak page 203 on WAI: https://archive.org/details/Programming_the_65816/page/n213
- snes9x implementation of WAI: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L3313
- undisbeliever on WAI: https://undisbeliever.net/snesdev/65816-opcodes.html#wai-wait-for-interrupt