When an interrupt OB has been completely executed and there are
further interrupts pending, the system program calls and processes the
OB with the next lowest priority.
The INTERRUPTS processing level is only exited when every active
signal state (low level) of an interrupt line on the S5 bus has been
dealt with and the corresponding OB has been completely processed.
Note
Interrupt-driven program execution cannot be interrupted by the
same interrupt occurring again.
Disabling interrupt-driven
processing
An interrupt-driven program is called at a block or STEP 5 operation
boundary in the cyclic program. This interrupt can cause problems when
a cyclic section of program must be processed within a certain time (e.g.
to achieve a certain reaction time) or when a series of operations must not
be interrupted (e.g. when reading or writing interdependent values).
If a program section must not be interrupted by interrupt-driven
processing, the following strategies are possible:
Interrupts at block boundaries
••
Program this program section so that it does not contain a block
change. Program sections that do not contain a block change can
then not be interrupted.
••
Use OB 122 with which you can disable the processing of process
interrupts for a specific program section. Remember, however, that
the timed interrupts are also disabled (refer to Section 6.3).
••
Program the STEP 5 operation ’IA’ (disable process interrupts).
With the operation ’RA’ (enable process interrupts) you can enable
interrupt processing again.
Between these two operations, no process interrupt-driven
program execution is permitted. The program section between
these two operations cannot be interrupted.
••
’IA’ and ’RA’ are only possible in function blocks (extended
operation set - refer to Section 3.5.4) and only apply to process
interrupts via IB 0.
Note
If a process interrupt is disabled using OB 22 or delayed using
OB 142, the RA operation is not effective.
RUN Mode
CPU 948 Programming Guide
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Содержание CPU 948
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Страница 72: ...Data Blocks CPU 948 Programming Guide 2 42 C79000 G8576 C848 04 ...
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Страница 324: ...Examples of Parameter Assignment CPU 948 Programming Guide 7 18 C79000 G8576 C848 04 ...
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Страница 370: ...Addressable System Data Area CPU 948 Programming Guide 8 46 C79000 G8576 C848 04 ...
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Страница 404: ...Operations with the Base Address Register BR Register CPU 948 Programming Guide 9 34 C79000 G8576 C848 04 ...
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Страница 522: ...PG Functions via the S5 Bus CPU 948 Programming Guide 11 38 C79000 G8576 C848 04 ...
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Страница 546: ...List of Key Words CPU 948 Programming Guide Index 6 C79000 G8576 C848 04 ...