Monitoring and Response Times of F-Systems
A.3 F-Related Monitoring Times for S7 Distributed Safety
Safety Engineering in SIMATIC S7
System Manual, 04/2006, A5E00109529-05
A-5
A.3.2
Minimum Monitoring Time for Safety-related Communication between the F-CPU
and F-I/O or between I-Slave and Slave via PROFIBUS DP
PROFIsafe Monitoring Time TPSTO
To ensure that monitoring does not respond when no faults are present, the selected
PROFIsafe monitoring time TPSTO must be sufficiently large:
TPSTO > 2 ☓ T 2 ☓ TTR + 2 ☓ TACK
Definition of Times
Time
Definition
Reference
TCImax
Maximum cycle time of relevant
OB
"Minimum Monitoring Time for F-Cycle Time"
TFPROG
Maximum runtime of safety
program
1
-
TDP_DLY
Additional DP time delay of a
PROFIBUS CP
(communications processor)
In
HW Config
: Object properties for CP,
"Operating Mode" tab
TTR
Maximum target rotation time for
the DP master system (relevant
for distributed F-I/O only)
In
HW Config
: Object properties
for DP master system, Bus parameters
TSlave
Only relevant for distributed
F-I/O in ET 200M, ET 200S and
ET 200pro:
Maximum response time of
distributed I/O system, that is,
maximum delay by the IM and
its backplane bus
Refer to the manuals for F-I/O to learn about
how to calculate these times.
TACK
Maximum acknowledgment time
of F-I/O (for F-SMs: in safety
mode)
You can find this time in the technical
specifications of the manuals for the fail-safe
modules or SMs.
1
Only relevant for fail-safe I/O with inputs or outputs
Check to Determine If Configured PROFIsafe Monitoring Time Is Too Short
Refer to the information in the corresponding section on "Minimum Monitoring Time for
Safety-Related Communication between F-CPU and F-I/O" for S7 F/FH systems.
Communication between F-CPU and F-I/O via PROFINET IO
Use the Microsoft Excel file provided with S7 Distributed Safety to calculate the minimum
monitoring time for PROFINET IO. The Excel file is available on the Internet under the
contribution ID 19138505 at
http://support.automation.siemens.com/WW/view/en/11669702/133100.
Read also the comments in the Excel file.
