ADSP-BF53x/BF56x Blackfin Processor Programming Reference
4-51
Program Sequencer
“Example Code for an Exception Handler” on page 4-68
uses the same
principle to handle an exception with normal interrupt priority level.
Nesting of Interrupts
Interrupts are handled either with or without nesting, individually. For
more information, see
“Return Registers and Instructions” on page 4-42
.
Non-nested Interrupts
If interrupts do not require nesting, all interrupts are disabled during the
interrupt service routine. Note, however, that emulation, NMI, and
exceptions are still accepted by the system.
When the system does not need to support nested interrupts, there is no
need to store the return address held in
RETI
. Only the portion of the
machine state used in the interrupt service routine must be saved in the
Supervisor stack. To return from a non-nested interrupt service routine,
only the
RTI
instruction must be executed, because the return address is
already held in the
RETI
register.
Figure 4-8
shows an example of interrupt handling where interrupts are
globally disabled for the entire interrupt service routine.
Nested Interrupts
If interrupts require nesting, the return address to the interrupted point in
the original interrupt service routine must be explicitly saved and subse-
quently restored when execution of the nested interrupt service routine
has completed. The first instruction in an interrupt service routine that
supports nesting must save the return address currently held in
RETI
by
pushing it onto the Supervisor stack (
[--SP] = RETI
). This clears the glo-
bal interrupt disable bit
IPEND[4]
, enabling interrupts. Next, all registers
that are modified by the interrupt service routine are saved onto the
Содержание ADSP-BF53x Blackfin
Страница 38: ...Conventions xxxviii ADSP BF53x BF56x Blackfin Processor Programming Reference...
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Страница 324: ...Instruction Overview 7 20 ADSP BF53x BF56x Blackfin Processor Programming Reference...
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Страница 742: ...Instruction Overview 19 54 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 752: ...Examples 20 10 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 780: ...Product Identification Register 21 28 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 790: ...ADSP BF535 Flags A 10 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 800: ...Performance Monitor Registers B 10 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 994: ...Instructions Listed By Operation Code C 194 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 1042: ...Index I 40 ADSP BF53x BF56x Blackfin Processor Programming Reference...