Parameters/address space
4.3 Explanation of parameters
Digital I/O module F-DI 4+F-DQ 2x24VDC/2A, 4xM12 (6ES7146-5FF00-0BA0)
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Equipment Manual, V1.0, 05/2021, A5E51082342-AA
When you select the channel group as 1oo2, STEP 7 (TIA Portal) enables the parameters in
the first channel of the group and completely disables the parameters in the second channel
of the group. The second channel derives its parameter values from the first channel's
parameter values. When you select the channel group as 1oo1, STEP 7 (TIA Portal) enables all
of the parameters in both channels.
Note
Safety program access to 1oo2 input data
For 1oo2 evaluation, two paired input channels (for example, F-DI 0 and F-DI 2) are
connected to one or two sensors. The F-DI performs the discrepancy analysis and sends the
result to the safety program, at the input address of the low-numbered channel of the pair (F-
DI 0, in the example).
Discrepancy behavior
A 1oo2 input configuration allows a logical difference between the two signals, without
error, for the configured discrepancy time. You assign the value that is supplied to the safety
program in the F-CPU during a discrepancy between two relevant input channels, which
means while discrepancy time is running. You assign the discrepancy behavior as follows:
•
"Supply last valid value"
•
"Supply value 0"
Note
Sensor-actuator response time is increased when you add more input discrepancy time
The discrepancy time adds directly to the maximum response time of a 1oo2 evaluation if the
two signals do not agree in logical state. If you select the "Supply value 0" option, then the
F-DI does not delay a transition from "1" to "0" but can delay the transition from "0" to "1". If
you select the "Supply last valid value" option, then the F-DI can delay both transitions from
"1" to "0' and "0" to "1". The discrepancy time is influenced by sensor specifications,
installation tolerances, and wiring. For best response time, select the smallest discrepancy
time that provides reliable normal operation. Refer to "Response times (Page 83)" for further
information.
Discrepancy time
The two signals in a 1oo2 input configuration will not change exactly at the same time, due
to differences in sensors, contacts, and wiring. You can configure a maximum expected
duration for a mismatch between signals during transition.
Reintegration after discrepancy error
You can assign whether a zero state must be detected on both 1oo2 inputs before a
previously declared discrepancy can be cleared.
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