Analog Devices ADSP-BF535 Blackfin, Hardware Reference Manual

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ADSP-BF535 Blackfin Processor Hardware Reference 4-39
Program Sequencer
As shown in Table 4-11 , exceptions can be services or error conditions.
The value in the Type column indicates whether the exception for that
row is a service or an error condition.
• For services (S), the return address is the address of the instruction
that follows the exception, because a service is never re-executed.
• To allow the program to resume execution on return from a service
routine, the processor state must be preserved before the excepting
instruction.
• For error conditions (E), the return address is the address of the
instruction that caused the exception, because some types of errors,
such as a page fault, require that the offending instruction be
re-executed.
• Determining whether the instruction is re-executed depends on the
excepting instruction and error condition and is determined by the
exception handler. When the instruction should be re-executed,
the return address is used. When the instruction should not be
re-executed, the exception handler must advance the return address
by the instruction length.
•
EXCAUSE[5:0]
is placed in the Sequencer Status register (
SEQSTAT
),
depending on the type of event.