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servicing a higher priority event takes precedence over servicing a lower
priority event. The controller provides support for five different types of
events:
• Emulation – Causes the processor to enter Emulation mode, allow-
ing command and control of the processor via the JTAG interface.
• Reset – Resets the processor.
• Nonmaskable Interrupt (NMI) – The software watchdog timer or
the NMI input signal to the processor generates this event. The
NMI event is frequently used as a power-down indicator to initiate
an orderly shutdown of the system.
• Exceptions – Synchronous to program flow. That is, the exception
is taken before the instruction is allowed to complete. Conditions
such as data alignment violations and undefined instructions cause
exceptions.
• Interrupts – Asynchronous to program flow. These are caused by
input pins, timers, and other peripherals.
Each event has an associated register to hold the return address and an
associated return-from-event instruction. When an event is triggered, the
state of the processor is saved on the supervisor stack.
The processor event controller consists of two stages: the Core Event Con-
troller (CEC) and the System Interrupt Controller (SIC). The CEC works
with the SIC to prioritize and control all system events. Conceptually,
interrupts from the peripherals arrive at the SIC and are routed directly
into the general-purpose interrupts of the CEC.
ADSP-BF53x/BF56x Blackfin Processor Programming Reference
Introduction
1-7
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