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S7-300 Automation System, Hardware and Installation: CPU 31xC and CPU 31x
A5E00105492-03
11-3
PIQ
transfer
Execute force
job for inputs
Execute force
job for inputs
T PQW
Besy
PII
transfer
User program
Forced value
Forced value
overwritten by
T PQW!
With S7-300 CPUs, forcing is the same as "cyclical modify"
OS: operating system execution
PIQ
transfer
Besy
PII
transfer
Forced value
Execute force
job for outputs
Execute force
job for outputs
Figure 11-1 Principle of forcing in S7-300 CPUs
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Table 11-1
The differences between forcing and modifying variables
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)RUFLQJ
0RGLI\LQJ9DULDEOHV
Memory bit (M)
-
Yes
Timers and counters (T, C)
-
Yes
Data Blocks (DB)
-
Yes
Inputs and outputs (I, Q)
Yes
Yes
Peripheral Inputs (PI)
-
-
Peripheral Outputs (PO)
-
Yes
User program can overwrite modify/force
values
Yes Yes
Maximum number of force values
10
-
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Details on test functions of the software are found in the
67(HOS
and
in the
67(33URJUDPPLQJ0DQXDO
.
Содержание CPU 312
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