Siemens SIMATIC S5-115U, User Manual

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Integral Blocks S5-115U Manual
11.2 Organization Blocks
Besides function blocks, organization blocks are also integrated in the CPUs of the S5-115U
programmable controller.
11.2.1 OB31 Scan Time Triggering
A scan time monitor monitors the program scan time. If program scanning takes longer than the
specified scan monitoring time (e.g., 500 msec.), the CPU enters the
"
STOP
"
mode.
This situation can occur, for instance, when
•
The control program is too long.
• The program enters a continuous loop.
The scan time monitor can be started at any point in the control program using the OB31 call
(JU OB31), i.e. the scan monitoring time is restarted.
Prerequisite: SYSTEM OPERATIONS enabled on the programmer.
The scan monitoring time can be set in the following ways:
•
In system data word 96 (EAC0
H
) (see Chapter 2)
• In DB1 (see Section 11.3).
11.2.2 OB160 Variable Time Loop
OB160 simulates operation execution times. This makes you independent of the different opera-
tion execution times of the various CPUs and you can program wait times uniformly for all CPUs of
the S5-115U range.
Proceed as follows:
The waiting time must be loaded into the ACCUM in
µ
sec. (range: 120 to 65535 or 78
H
to FFFF
H
).
Example:
A waiting time of one millisecond is to be programmed.
L KF +1000
JU OB 160.
Please note the following when programming OB160:
A process interrupt (OB2 to OB5) and the timed interrupt (OB6) can interrupt the waiting time
(provided no interrupt disable (IA) has been programmed). The waiting time stops during the in-
terrupt! Similarly, the waiting time is increased by running PG/OP operations. The times set are
therefore minimum times!
OBs 10 to 13 cannot interrupt OB160!
*In the case of CPU 944: 190 µ s
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EWA 4NEB 811 6130-02b