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3.1.11.4
Supply voltage status
The two green LED's in the controller supply section, display the status of the
supply voltage. The left LED (A) indicates the status of the 24 V supply for
the coupler. The other LED ('B' or 'C') displays the status of the field side
supply (i.e., the power jumper contacts).
LED
A
Green
OFF
B or C
Green
OFF
3.1.12 Fault behavior
3.1.12.1
Fieldbus failure
When a Modbus TCP fieldbus failure occurs (e.g., the Ethernet cable is
removed or broke), the outputs that are controlled by the fieldbus port remain
in their current state by default. If this behavior is undesirable, a fieldbus
watchdog timer can be programmed to monitor Fieldbus communications.
The watchdog monitors the data transfer between the master controls and the
PFC. In the event of a watchdog timeout (i.e., there is a Fieldbus failure), the
PFC can be programmed to control the state of the outputs, based on your
application needs. In the case of fault free communications, the watchdog
timer will not timeout, since after each successful data transfer the watchdog
timer is reset.
Monitoring the watchdog time in the PFC is done by using the function block
'FBUS_ERROR_INFORMATION' in the control program. This function is
part of the "mod_com.lib" library.
Fig. 3.1-17: Function block for determining a fieldbus failure
'FBUS_ERROR' (BOOL) = FALSE = no fault
'ERROR' (WORD)
WAGO-I/O-SYSTEM 750
ETHERNET TCP/IP
Meaning
Operating voltage for the system exists.
No operating voltage for the system.
Operating voltage for the power jumper
contacts exists.
No operating voltage for the the power
jumper contacts.
= TRUE = fieldbus failure
= 0
= 1
Fieldbus Controller
Fieldbus Controller 750-872/020-000
Trouble shooting
Check the supply voltage (24V
and 0V).
Check the supply voltage (24V
and 0V).
= no fault
= fieldbus failure
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g012926x
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