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Siemens TX-I/O™ Module system – Functions and operation CM110561en_08
Building Technologies Digital input functions 2018-10-25
• The signal is read at regular intervals and debounced on hardware level
• An additional debounce time is available: 0…25.5 s (default = 0 s)
• Pulses of more than 20 ms from pushbuttons are registered and kept ready for
polling
• Desigo XWORKS plus: Only D20 (N/O) is available. Inversion (D20R, N/C) must
be realized via inverting in the parameterization.
• P-Bus BIM : The configuration (D20. D20R) sets the contact type (N/O or N/C)
• The meaning of the I/O status LED can be parameterized (TXM1.8D only):
Normal = green (default) / Alarm = Red / Service = Yellow.
• The signal operation can be selected: Contact_NO (default), Contact_NC)
• As a result
– The I/O status LED is activated.
– The process value is communicated over the bus
– The LCD is activated
Digital inputs cannot be overridden locally. The override button has no effect, and if an
attempt is made to operate it, an error is displayed.
• The I/O status LED shows the source signal
• The LCD panel (if available) shows the source signal type (status contact, N/O or
N/C contact) and the state of the contact:
N/C contact
Process value island bus
Process value
LCD-Display
I/O status LED
closed
open
active
inactive
10561z155
ON
OFF
N/O
N/C
> 20 ms
200 ms
P-Bus Polling
N/O
> 20 ms
Diagram: Cause and effect
For details, especially in relation to flashing pattern and errors: refer to the section "Dis-
play, operation and diagnostics" in the TX-I/O™ Engineering and installation guide [6].
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