Fig. 4-2 Principle of changing level and the ISTACK
Example of
"Interrupting a basic level with interruptability at block
boundaries":
A timed interrupt occurs while a process interrupt is being serviced.
Since the timed interrupt has a higher priority, the servicing of the
PROCESS INTERRUPT is interrupted at the next block boundary and the
TIMED INTERRUPT level nested in. If an addressing error now occurs
while servicing the timed interrrupt, the timed interrupt servicing is
interrupted immediately at the next operation boundary to nest in the
ADF level.
Program Execution Levels
CPU 948 Programming Guide
4 - 8 C79000-G8576-C848-04
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