4.4.2
Specifying Time and
Interrupt-Driven Program
Execution
With time and interrupt-driven program execution, various types are
available which can at present only be used as alternatives (i.e. not
mixed). You decide which of the types of processing you want to use
by setting the parameter in data block DX 0 (refer to Chapter 7).
"Process interrupts via IB 0"
The execution mode "process interrupts via IB 0" has the following
features:
•• only possible in single processor operation,
•• the nesting of higher priority program levels is only possible at
block boundaries,
•• the delayed interrupt (processed by OB 6) cannot be used,
•• the time-controlled interrupt (processing by OB 9) cannot be used.
"System interrupts" mode
The "system interrupts" mode is characterized by the following
features:
•• single or multiprocessor mode possible,
•• higher priority program levels are nested at block or command
boundaries,
•• delayed interrupts are processed by OB 6,
•• time-controlled interrupts are processed by OB 9.
Interrupting time and
interrupt-driven program
execution
Time and interrupt-driven program execution can be interrupted or
aborted regardless of the parameter setting in DX 0 as follows:
•• when a device fault or program error occurs (at operation
boundaries,
•• by operator intervention:
- stop switch, HALT (at operation boundaries),
- PG function (at checkpoints - refer to Chapter 11),
•• by the stop command STS (at operation boundaries),
•• by a power failure on the central controller or in the expansion unit
(at operation boundaries).
RUN Mode
CPU 948 Programming Guide
4 - 32 C79000-G8576-C848-04
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