Interrupts With and Without Nesting
4-54
ADSP-BF535 Blackfin Processor Hardware Reference
The return-from-interrupt instruction,
RTI
, is sensitive to the state of
RETI[0]
and
SNEN
. When both
RETI[0]
and
SNEN
are set,
RTI
clears only
the global disable bit
IPEND[4]
. However, when self-nesting mode is dis-
abled (
SNEN = 0
),
RTI
clears both
IPEND[4]
and the
IPEND
bit that
corresponds to the current interrupt level.
The
SNEN
bit should be set once in the reset service routine and not
changed again during normal interrupt processing.
Since the LSB of the RETI register is used to store the self-nesting state,
avoid changing the contents of the RETI register when self-nesting is
enabled, except for saving and restoring the register to the stack.
Exception Handling
Interrupts and exceptions treat instructions in the pipeline differently:
• When an interrupt occurs, all instructions in the pipeline are
aborted.
• When an exception occurs, all instructions in the pipeline after the
excepting instruction are aborted. For service exceptions, the
excepting instruction is also aborted.
Because exceptions, NMIs, and emulation events have a dedicated return
register, guarding the return address is optional. Consequently, the push
and pop instructions for exceptions, NMIs, and emulation events do not
affect the interrupt system.
Note, however, the return instructions for exceptions (
RTX
,
RTN
, and
RTE
)
do clear the least significant bit currently set in
IPEND
.
Summary of Contents for ADSP-BF535 Blackfin
Page 80: ...Development Tools 1 26 ADSP BF535 Blackfin Processor Hardware Reference...
Page 312: ...Working With Memory 6 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 332: ...System Interfaces 7 20 ADSP BF535 Blackfin Processor Hardware Reference...
Page 360: ...Dynamic Power Management Controller 8 28 ADSP BF535 Blackfin Processor Hardware Reference...
Page 446: ...Beginning and Ending an SPI Transfer 10 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 522: ...Timing Examples 11 76 ADSP BF535 Blackfin Processor Hardware Reference...
Page 562: ...IrDA Support 12 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 608: ...PCI I O Issues 13 46 ADSP BF535 Blackfin Processor Hardware Reference...
Page 672: ...References 14 64 ADSP BF535 Blackfin Processor Hardware Reference...
Page 810: ...SDRAM Controller SDC 18 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 811: ...ADSP BF535 Blackfin Processor Hardware Reference 18 87 External Bus Interface Unit...
Page 812: ...SDRAM Controller SDC 18 88 ADSP BF535 Blackfin Processor Hardware Reference...
Page 860: ...DMA Bus Debug Registers 20 30 ADSP BF535 Blackfin Processor Hardware Reference...