
Description of Operation
4-6
ADSP-BF59x Blackfin Processor Hardware Reference
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, the
SIC_ISR
register will seldom, if ever, need to be interrogated.
The
SIC_ISR
register is not affected by the state of the
SIC_IMASK
register
and can be read at any time. Writes to the
SIC_ISR
register have no effect
on its contents.
Peripheral DMA channels are mapped in a fixed manner to the peripheral
interrupt IDs. However, the assignment between peripherals and DMA
channels is freely programmable with the
DMA_PERIPHERAL_MAP
registers.
Table 4-1 on page 4-3
and
Table 4-2 on page 4-11
show the default DMA
assignment. Once a peripheral has been assigned to any other DMA chan-
nel it uses the new DMA channel’s interrupt ID regardless of whether
DMA is enabled or not. Therefore, clean
DMA_PERIPHERAL_MAP
manage-
ment is required even if the DMA is not used. The default setup should be
the best choice for all non-DMA applications.
For dynamic power management, any of the peripherals can be configured
to wake up the core from its idled state to process the interrupt, simply by
enabling the appropriate bit in the
SIC_IWR
register (refer to
Table 4-1 on
page 4-3
and
Table 4-2 on page 4-11
). If a peripheral interrupt source is
enabled in
SIC_IWR
and the core is idled, the interrupt causes the DPMC
to initiate the core wakeup sequence in order to process the interrupt.
Note this mode of operation may add latency to interrupt processing,
depending on the power control state. For further discussion of power
modes and the idled state of the core, see the Dynamic Power Manage-
ment chapter.
The
SIC_IWR
register has no effect unless the core is idled. By default, all
interrupts generate a wakeup request to the core. However, for some
Содержание ADSP-BF59x Blackfin
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