Monitoring and Response Times of F-Systems
A.4 F-Related Monitoring Times for S7 F/FH Systems
Safety Engineering in SIMATIC S7
System Manual, 04/2006, A5E00109529-05
A-9
A.4.1
Minimum Monitoring Time for F-Cycle Time
MAX_CYC Parameter in F_CYC_CO
The monitoring time is assigned in the MAX_CYC input parameter of F-block F_CYC_CO.
The F_CYC_CO F-block is automatically inserted by
S7 F Systems in a separate F-runtime
group in the safety program when the safety program is compiled. When the F_CYC_CO
block is positioned, a dialog box is displayed for entering the MAX_CYC parameter.
To ensure that monitoring does not respond when no errors are present, the selected
MAX_CYC must be greater than the maximum cycle time of the associated TCImax time
interrupt OB:
MAX_CYC > TCImax
The maximum cycle time of the associated TCImax time interrupt OB is at least as large as
the configured cycle time of the TCI time interrupt OB . In S7 FH Systems, the maximum
disabling time for priority classes > 15 (TP15) must also be taken into account when
updating.
Extending the Maximum Cycle Time Using CiR:
If "Configuration in RUN (CiR)" is used, the maximum cycle time is extended by the lesser of
the following two values:
•
CiR synchronization time of F-CPU
The CiR synchronization time of the F-CPU is the sum of the CiR synchronization times
for all DP master systems that are to be changed simultaneously. The CiR
synchronization time of a DP master system is displayed in
HW Config in the properties
dialog for the relevant CiR object.
•
Upper limit of CiR synchronization time
The default value for the upper limit is 1 s. You can increase or decrease this value
according to your requirements by calling SFC 104 "CiR".
Thus, the following approximation formulas are applicable:
Formula
Where?
TCImax ≈ TCI + MIN(TCiR; 2500)
2
In S7 F-Systems
TCImax ≈ MAX (TCI; TP15)
1
+ MIN(TCiR; 2500)
2
In S7 FH Systems with time interrupt OB
with special handling
TCImax ≈ TCI + TP15 + MIN(TCiR; 2500)
2
In S7 FH Systems with time interrupt OB
without special handling
1
Use the greater of the two values
2
Use the lesser of the two values
