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RUN Mode
Triggering
User interfaces
OB 2 to OB 5
Priority of process interrupts
4 - 44
The active state of an interrupt line on the S5 bus triggers the
interrupt. The interrupt signal is level-triggered (low level). To
acknowledge the interrupt, please refer to the operating instructions
for the module which triggers the interrupt.
If an interrupt occurs, one of the OBs listed in the following table is
called as the user interface.
Table 4-8
User interfaces for interrupts
Interrupt triggered by
Interrupt signal X
(A, B, C or D, slot-dependent)
Interrupt signal E
Interrupt signal F
Interrupt signal G
If, for example, the interrupt signal 'F' occurs, the system program
calls OB 4.
If the relevant OB is not loaded, program execution is not interrupted.
There is no interrupt-driven program execution.
The default setting means that PROCESS INTERRUPTS have a lower
priority than the TIMED INTERRUPTS level.
A parameter in data block DX 0 allows you to change the default so
that the process interrupts level has a higher priority than the TIMED
INTERRUPTS level.
Within interrupt servicing, the priorities of the individual interrupts
are specified as follows:
• • If there are several interrupts pending, the corresponding
organization blocks are called according to the order of priority
you specify in DX 0 (single priority).
You can specify priority levels 1 to 5 for the four interrupts.
OB called
OB 2
OB 3
OB 4
OB 5
CPU 948 Programming Guide
C79000-G8576-C848-04
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