Description of Operation
4-8
ADSP-BF537 Blackfin Processor Hardware Reference
of whether the particular interrupt is enabled at the peripheral itself. At
reset, the contents of
SIC_IMASK
are all 0s to mask off all peripheral inter-
rupts. Turning off a system interrupt mask and enabling the particular
interrupt is performed by writing a 1 to a bit location in
SIC_IMASK
.
The SIC includes a read-only system interrupt status register (
SIC_ISR
)
with individual bits which correspond to one of the peripheral interrupt
sources. See
. When the SIC detects the interrupt,
the bit is asserted. When the SIC detects that the peripheral interrupt
input has been deasserted, the respective bit in the system interrupt status
register is cleared. Note for some peripherals, such as programmable flag
asynchronous input interrupts, many cycles of latency may pass from the
time an interrupt service routine initiates the clearing of the interrupt
(usually by writing a system MMR) to the time the SIC senses that the
interrupt has been deasserted.
Depending on how interrupt sources map to the general-purpose interrupt
inputs of the core, the interrupt service routine may have to interrogate
multiple interrupt status bits to determine the source of the interrupt.
One of the first instructions executed in an interrupt service routine
should read
SIC_ISR
to determine whether more than one of the peripher-
als sharing the input has asserted its interrupt output. The service routine
should fully process all pending, shared interrupts before executing the
RTI, which enables further interrupt generation on that interrupt input.
L
When an interrupt’s service routine is finished, the RTI instruction
clears the appropriate bit in the
IPEND
register. However, the rele-
vant
SIC_ISR
bit is not cleared unless the service routine clears the
mechanism that generated the interrupt.
Many systems need relatively few interrupt-enabled peripherals, allowing
each peripheral to map to a unique core priority level. In these designs,
SIC_ISR
will seldom, if ever, need to be interrogated.
Summary of Contents for Blackfin ADSP-BF537
Page 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Page 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 876: ...Programming Examples 14 36 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 938: ...Programming Examples 15 62 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...