Siemens TX-I/O TXM1.8D Functions And Operation page 51

Local override
Display
Response in the
event of a fault
When fault is repaired
Siemens
Building Technologies
• When detected, a new process value is processed.
• The output is a control voltage in the range DC 0... 10 V
or a control current in the range DC 4 ... 20 mA
• The process value is indicated via the I/O status LED,
and on the LCD panel, if available
• The output value can be overridden manually
• Local override has first priority, followed by tool override and (lastly) operation via
process value
• Tool override of an I/O point is indicated by the flashing of the module status LED.
• Pressing the override button in the middle enables/disables the local override.
The yellow "Override" LED indicates that local override is active
• When local override is active:
Pressing "+" increases the value of the analog output by 10%.
Repeated or sustained pressure switches changes the value by several stages until
the function stops at the highest value.
Pressing "–" reduces the value of the analog output by 10%.
Repeated or sustained pressure switches changes the value by several stages until
the function stops at the lowest value.
The I/O status LED and LCD display change accordingly.
• With a change from automatic operation to local override, the process value (and
thus the status of the devices concerned) is retained until the user overrides it.
the same applies after resumption of automatic operation, until the bus master sends
a new process value.
For a full description see page 9.
• The brightness of the I/O status LED varies in proportion to the output value
• If an LCD panel is available, it indicates the signal type
(DC 0 ... 10 V, DC 4 ... 20 mA) and displays the value in graphic form.
For details, especially in relation to flashing pattern and errors: refer to the section
"Display, operation and diagnostics" in the TX-I/O™ Engineering and installation guide
[6].
• The process values on the bus are monitored for compliance with their admissible
range
• The DC 24 V module supply voltage is monitored
• Faults are indicated to the bus master
• In the event of bus failure the module keeps the last valid value.
• If the DC 24 V bus supply fails, the output signal always goes to 0. When the supply
is restored, the signal remains at 0 until a valid process value becomes available.
• in the case of bus failure:
The behavior can be parameterized for each I/O point:
– Backup Mode = Keep
– Backup Mode = No (default)
– Backup Mode = Value
P-bus BIM: The module keeps the last valid values
Operation in the same state as before the fault:
automatic operation, remote override or local override
TX-I/O™ Module system – Functions and operation
Analog output functions
Last active value
Smallest value (0V, 4mA)
Configurable value (Backup Value)
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CM110561en_08
2018-10-25