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RTI: Difference between revisions
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=== External Links === | === External Links === | ||
* [[Eyes & Lichty]] page 492, on RTI: https://archive.org/details/0893037893ProgrammingThe65816/page/492 | * [[Eyes & Lichty]] page 492, on RTI: https://archive.org/details/0893037893ProgrammingThe65816/page/492 | ||
* [[Labiak]] | * [[Labiak]], [https://archive.org/details/Programming_the_65816/page/n186 page 176] on RTI | ||
* [[MCS6500 Manual]] page 132 on RTI: https://archive.org/details/mos_microcomputers_programming_manual/page/n152 | * [[MCS6500 Manual]] page 132 on RTI: https://archive.org/details/mos_microcomputers_programming_manual/page/n152 | ||
* [[Carr]] page 270 on RTI: https://archive.org/details/6502UsersManual/page/n283 | * [[Carr]] page 270 on RTI: https://archive.org/details/6502UsersManual/page/n283 | ||
Revision as of 04:25, 6 August 2024
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Stack (RTI) | 40 | 1 byte | 7 cycles* | ||||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| N | V | M | X | D | I | Z | C | |
| 65c816 native mode | N | V | M | X | D | I | Z | C |
| 6502 emulation mode | N | V | . | . | D | I | Z | C |
RTI (ReTurn from Interrupt) is a 65x instruction used to return control from an interrupt handler. It does this by first pulling the status flags off of the stack and then the program counter too. In native mode, the program bank register is pulled after that for a total of 4 bytes. In emulation mode, 3 bytes are pulled.
Syntax
RTI
Pitfalls
- RTI should only be run when the e flag is in the same state as when the interrupt fired
- RTI cannot even tell whether the interrupt actually occurred or not
- RTI does not increment the program counter after pulling it like RTS and RTL do
Cycle Skipped
RTI takes one fewer cycle in emulation mode as the program bank register doesn't need to be pulled from the stack.
See Also
External Links
- Eyes & Lichty page 492, on RTI: https://archive.org/details/0893037893ProgrammingThe65816/page/492
- Labiak, page 176 on RTI
- MCS6500 Manual page 132 on RTI: https://archive.org/details/mos_microcomputers_programming_manual/page/n152
- Carr page 270 on RTI: https://archive.org/details/6502UsersManual/page/n283
- Leventhal page 3-89 on RTI: https://archive.org/details/6502-assembly-language-programming/page/n138
- snes9x implementation of RTI: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L3272
- undisbeliever on RTI: https://undisbeliever.net/snesdev/65816-opcodes.html#rti-return-from-interrupt
- Pickens, John. http://www.6502.org/tutorials/6502opcodes.html#RTI
- Clark, Bruce. http://www.6502.org/tutorials/65c816opcodes.html#6.3.2
- lbid, APPENDIX: EMULATION MODE, http://www.6502.org/tutorials/65c816opcodes.html#APPENDIX: