Interrupts With and Without Nesting
4-50
ADSP-BF535 Blackfin Processor Hardware Reference
Figure 4-16
illustrates that by pushing
RETI
onto the stack, interrupts can
be re-enabled during an ISR, resulting in only a short duration where
interrupts are globally disabled.
Figure 4-16. Nested Interrupt Handling
Interrupts disabled
during this interval.
A1
I3
I0 I1
A8
Note that ISR
return may be
accelerated by
popping RETI ear-
lier, and starting
return address
fetch earlier. The
cost is a longer
per iod during
which interrupt
system is off.
A0
Pipeline
stage
IF1
IF2
DC
AC
EX1
EX2
EX3
WB
ILAT
IPEND
0x0100
0x8000
ILAT
IPEND
0x0000
0x8110
ILAT
IPEND
0x0000
0x8000
Instruction I3 is RTI.
Clear IPEND[8],
IPEND[4], jump to
return address.
Instruction A1 is
return address.
Inter rupt is accepted.
Bit ILAT[8] cleared
and IPEND[8] set.
Return address
placed in RETI. Bit
IPEND[4] set until
RET I is s aved.
Change processor
mode.
Interrupt 8 is
latched, s o bit
ILAT[8] is set. I0
is first instruc-
tion in ISR.
Assume that
low priority
interrupt is cur-
rently being ser-
viced. A0 is the
last executed
instruction.
Dashed lines
indicate abor ts
(A1-A8), which
are r e-issued at
the completion
of the interrupt.
I2
ILAT
IPEND
0x0000
0x8110
Instruction I2 pops
RETI, and sets
IPEND[4] to disable
interrupts until RT I.
Interrupts
disabled during
this interval.
ILAT
IPEND
0x0000
0x8100
Instruction I1 pushes
RETI on stack. Bit
IPEND[4] cleared. All
interrupts of priority
higher than 8 enabled.
Содержание ADSP-BF535 Blackfin
Страница 80: ...Development Tools 1 26 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 312: ...Working With Memory 6 86 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 332: ...System Interfaces 7 20 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 360: ...Dynamic Power Management Controller 8 28 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 446: ...Beginning and Ending an SPI Transfer 10 40 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 522: ...Timing Examples 11 76 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 562: ...IrDA Support 12 40 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 608: ...PCI I O Issues 13 46 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 672: ...References 14 64 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 810: ...SDRAM Controller SDC 18 86 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 811: ...ADSP BF535 Blackfin Processor Hardware Reference 18 87 External Bus Interface Unit...
Страница 812: ...SDRAM Controller SDC 18 88 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 860: ...DMA Bus Debug Registers 20 30 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 908: ...SDRAM Controller External Bus Interface Unit B 36 ADSP BF535 Blackfin Processor Hardware Reference...