Analog Devices ADSP-BF53x Blackfin Reference page 178

Events and Interrupts
If there is not a need for non-interruptible code inside the service routine,
it is good programming practice to enable nesting immediately. This
avoids unnecessary delay to high priority interrupt routines. For example:
isr:
[--SP] = RETI;
[--SP] = (R7:0, P5:0);
[--SP] = ASTAT;
/* place core of service routine here */
ASTAT = [SP++];
(R7:0, P5:0) = [SP++];
RETI = [SP++];
RTI; /* return from interrupt */
isr.end:
See "Nesting of Interrupts" on page 4-51
nesting.
Emulation Events, NMI, and Exceptions use a technique similar to "nor-
mal" interrupts. However, they have their own return register and return
instruction counterparts.
Table 4-9. Return Registers and Instructions
Name Event Class
EMU Emulation
RST Reset
NMI NMI
EVX Exception
Reserved Reserved
IVHW Hardware Error
IVTMR Core Timer
IVG7 Interrupt 7
4-44 ADSP-BF53x/BF56x Blackfin Processor Programming Reference
/* enable nesting */
/* push core registers */
/* push arithmetic status */
/* pop arithmetic status */
/* pop core registers */
/* disable nesting */
Table 4-9 provides an overview.
Return Register
RETE
RETI
RETN
RETX
-
RETI
RETI
RETI
for more details on interrupt
Return
Instruction
RTE
RTI
RTN
RTX
-
RTI
RTI
RTI