Fail-Safe signal module (SM) I/O configuration
5.4 Configuring SM 1226 F-DQ 4 x 24 VDC DQ and channel parameters
S7-1200 Functional Safety Manual
112 Manual, 02/2015, A5E03470344-AA
Table 5- 5 SM 1226 F-DQ 4 x 24 VDC channel parameters
Activated Select the check box to activate the channel.
Deselect the check box and the unused
channel is deactivated.
If you deactivate a channel, you also deacti-
vate its diagnostic function.
Check box select-
ed
Check box:
• Selected
• Deselected
Channel failure
acknowledge
Controls whether the channel is automatically
reintegrated after a fault clears, or requires an
acknowledgement (manual) in the user pro-
gram. Refer to "Reactions to faults"
(Page 115) for the reintegration procedure.
Manual
• Automatic
• Manual
Maximum readback time The maximum readback time is a user-
configured parameter that assigns the maxi-
mum time allowed for an output to reach the
new state (ON or OFF) due to a process
value change without generating an error.
Also, this is the maximum width of a diagnos-
tic test pulse applied to verify that an output
can be turned OFF while it is ON. The time of
the OFF pulse should be as long as possible,
but short enough so that the actuator cannot
2.0 ms 1 ms to 400 ms,
in 0.1 ms increments
Maximum readback time
switch on test
The maximum readback time switch on test is
a user-configured parameter that assigns the
maximum time for which the P-switch or the
M-switch of a channel that is currently in OFF
state can be switched ON during a bit pattern
test step. The F-DQ DC tests the P- and M-
switches on a channel such that only one
switch is turned on at a time. Unless there is a
fault in the system (for example, actuator
shorted to ground), the actuator is not ener-
gized during either the P- or M-switch on
tests. Under single fault conditions (either
internal or external to the SM), test pulses
applied to either the P- or the M-switch of
channels in the OFF state can repeatedly
energize the actuator. You must select the
parameter so that the duration of such pulses
is too short to cause the actuator to react and,
therefore, cannot have a hazardous effect on
the equipment under control.
1.0 ms 0.5 ms to 5 ms,
in 0.1 ms increments
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