Siemens SIMATIC S7 Functional Safety Manual page 44

Getting started
2.2 Configuring
3. Return to the "Device view" and select the F-DQ 4x24VDC_1. Under the "Properties" tab,
select the "IO tags" tab. This action displays the "Process value" and "Quality" bits for the
fail-safe module. Here, you can define tags for each channel:
Each Process value bit has an associated Quality bit that reports whether the
corresponding process value is good. Quality bits are ON for good quality and OFF for
bad quality. If an entire module or channel is passivated, the associated Quallity bits are
OFF.
To check the Process value bits and the Quality bits, you must know where these bits are
mapped in the module. For an F-DQ 4x24VDC_1, the first four bits of the output (Q)
image register are the Process value bits, and the first four bits of the input (I) image
register are the Quality bits. For example, if the module starting address is I17.0 and
Q17.0 for the F-DQ 4x24VDC_1, then the Process value bits and corresponding Quality
bits are allocated as shown in the following table:
4. Under the "Properties" tab, select the "General" tab, and then select the "F-parameters"
area. Here, you can change the following parameters or accept the default settings:
– "F-monitoring time": A valid current safety message frame must be received from the
– "F-destination address": A unique PROFIsafe address is critical for every F-IO used in
Leave the settings unchanged for the F-parameters for this example.
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Process value
Q17.0
Q17.1
Q17.2
Q17.3
fail-safe CPU to the F-DQ DC within the F-monitoring time. Otherwise, the F-DQ DC
goes to safe state. The F-monitoring time must be set high enough so that message
frame delays are tolerated and, at the same time, low enough that the process can
react as quickly as possible when a fault occurs and run without impairment. By
default, the F-DQ DC's F-monitoring time is taken from the "Default F-monitoring time
for central F-I/O" parameter of the fail-safe CPU.
a safety system (network and CPU-wide). Refer to the "SIMATIC, Industrial Software,
SIMATIC Safety - Configuring and Programming, Programming and Operating
Manual" (http://support.automation.siemens.com/WW/view/en/54110126/0/en) for
procedures to set and verify unique PROFIsafe addresses in networked systems.
Quality bit
I17.0
I17.1
I17.2
I17.3
S7-1200 Functional Safety Manual
Manual, 02/2015, A5E03470344-AA