Interrupts With and Without Nesting
4-58
ADSP-BF535 Blackfin Processor Hardware Reference
• If a program mistakenly uses
RTX
,
RTN
, or
RTE
to return from an
interrupt, the core branches to the address in the corresponding
return register (
RETX
,
RETN
,
RETE
) and leaves
IPEND
unaffected.
• If a program mistakenly uses
RTI
or
RTX
to return from an NMI
routine, the core branches to the address in the corresponding
return register (
RETI
,
RETX
), and clears the bit in
IPEND
that corre-
sponds to the return instruction.
• In the case of
RTX
, bit
IPEND[3]
is cleared. In the case of
RTI
, the bit
of the highest priority interrupt in
IPEND
is cleared.
Recommendation for Allocating the System Stack
The software stack model for processing exceptions implies that the
Supervisor stack must never generate an exception while the exception
handler is saving its state. However, if the Supervisor stack grows past a
CPLB entry or SRAM block, it may, in fact, generate an exception.
To guarantee that the Supervisor stack never generates an exception—
never overflows past a CPLB entry or SRAM block while executing the
exception handler—calculate the maximum space that all interrupt service
routines and the exception handler occupy while they are active, and then
allocate this amount of SRAM memory.
Latency in Servicing Events
In some DSP architectures, if instructions are executed from external
memory and an interrupt occurs while the instruction fetch operation is
underway, then the interrupt is held off from being serviced until the cur-
rent fetch operation has completed. Consider a processor operating at
300 MHz and executing code from external memory with 100 ns access
times. Depending on when the interrupt occurs in the instruction fetch
operation, the interrupt service routine (ISR) may be held off for around
30 instruction clock cycles. When cache line fill operations are taken into
account, the ISR could be held off for many hundreds of cycles.
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...