Freescale Semiconductor StarCore SC140 - Manual (Page 684)

A-370 SC140 DSP Core Reference Manual
RTS
RTS
Return From Subroutine (AGU)
RTS
Description
Note: Because RTS uses the RAS mechanism, returning from an exception using RTS is illegal. The result
is undefined.
Status and Conditions that Affect Instruction
Status and Conditions Changed by Instruction
None.
Example
rts
Operation Assembler Syntax
If (RAS valid), then RAS
→ PC;
else (SP – 8)
→ PC;
always SP – 8
→ SP
RTS
RTS
Returns from a subroutine. If the RAS is valid, the PC is restored from the RAS. Otherwise, the PC is
popped from the active stack in memory as a 32-bit long word. The stack pointer always decrements by 8,
RAS becomes invalid, and program execution continues at the address specified in the PC.
Register Address Bit Name Description
SR[18] EXP Determines which stack pointer is used.
Register/Memory Address Before After
SR $00E4 0000
ESP $0000 2008 $0000 2000
($2000) $0000 0018
RAS $0000 0018
PC $0000 0026 $0000 0018