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RTS: Difference between revisions
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'''RTS''' (Return from Subroutine) is a 65x instruction used to return control from a subroutine that was called from the same [[bank]]. | '''RTS''' (Return from Subroutine) is a 65x instruction used to return control from a subroutine that was called from the same [[bank]]. | ||
RTS pulls the [[return address]] from the [[stack]], but increments the value by one before loading it into the [[program counter]]. | RTS pulls the [[return address]] from the [[stack]], but increments the value by one before loading it into the [[program counter]]. In other words, RTS unwinds what [[JSR]] did to the stack. The [[stack pointer]] is incremented twice: during cycle 3 and cycle 4. | ||
No flags are affected. | No flags are affected. | ||
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RTS | RTS | ||
</pre> | </pre> | ||
[[File:rts.png]] | |||
Forgetting to RTS can cause [[derailment]] as control falls through the end of the subroutine into the next one or garbage. | Forgetting to RTS can cause [[derailment]] as control falls through the end of the subroutine into the next one or garbage. | ||
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* Pickens, John. http://www.6502.org/tutorials/6502opcodes.html#RTS | * Pickens, John. http://www.6502.org/tutorials/6502opcodes.html#RTS | ||
* Clark, Bruce. http://www.6502.org/tutorials/65c816opcodes.html#6.2.2.2 | * Clark, Bruce. http://www.6502.org/tutorials/65c816opcodes.html#6.2.2.2 | ||
* https://archive.org/details/mos_microcomputers_programming_manual/page/n128 | |||
Latest revision as of 20:00, 10 August 2024
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Stack (RTS) | 60 | 1 byte | 6 cycles | ||||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| N | V | M | X | D | I | Z | C | |
| . | . | . | . | . | . | . | . | |
RTS (Return from Subroutine) is a 65x instruction used to return control from a subroutine that was called from the same bank.
RTS pulls the return address from the stack, but increments the value by one before loading it into the program counter. In other words, RTS unwinds what JSR did to the stack. The stack pointer is incremented twice: during cycle 3 and cycle 4.
No flags are affected.
Syntax
RTS
Forgetting to RTS can cause derailment as control falls through the end of the subroutine into the next one or garbage.
See Also
External Links
- Eyes & Lichty, page 496 on RTS
- Labiak, page 178 on RTS
- 8.2 on MCS6500 Manual, page 108 on RTS
- Carr, page 271 on RTS
- Leventhal, page 3-90 on RTS
- snes9x implementation of RTS: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L2982
- Pickens, John. http://www.6502.org/tutorials/6502opcodes.html#RTS
- Clark, Bruce. http://www.6502.org/tutorials/65c816opcodes.html#6.2.2.2
- https://archive.org/details/mos_microcomputers_programming_manual/page/n128