100 • Fieldbus Controller 750-841
Fault behavior
3.1.8.5 ‘USR‘-LED
The state of the ‘USR‘ LED is programmable with WAGO-I/O-PRO CAA. Functions in the program library ”Visual.lib“ can be used to control the LED state. One of the many possible uses of this LED is to indicate the RUN/STOP state of your controller.
3.1.8.6 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 controller. The right LED (B or C) displays the status of the field side supply (i.e., the power jumper contacts).
LED |
Meaning |
Trouble shooting |
A |
|
|
green |
Operating voltage for the system exists. |
|
OFF |
No operating voltage for the system. |
Check the supply voltage (24V and 0V). |
B or C |
|
|
green |
Operating voltage for the power jumper contacts |
|
|
exists. |
|
OFF |
No operating voltage for the the power jumper |
Check the supply voltage (24V and 0V). |
|
contacts. |
|
3.1.9 Fault behavior
3.1.9.1 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. 3-16: Function block for determining a fieldbus failure |
g012926x |
WAGO-I/O-SYSTEM 750
ETHERNET TCP/IP
Fieldbus Controller 750-841 • 101
Fault behavior
'FBUS_ERROR' (BOOL) = FALSE = no fault
|
= TRUE = fieldbus failure |
|
'ERROR' (WORD) |
= 0 |
= no fault |
|
= 1 |
= fieldbus failure |
More information
For detailed information to the Watchdog register see the Chapters "MODBUS Functions"; "Watchdog (Fieldbus failure)" and "Watchdog Register".
3.1.9.2 Internal bus fault
When an internal bus fault occurs (e.g., an I/O module is removed), all output modules turn off. Additionally, the "I/O" LED blinks red and generates a fault message. This message is decoded from the blink code, in the form of a fault code and fault argument.
Once the internal bus fault is fixed, the controller is restarted by cycling its power. At this point the transfer of the process data resumes and the outputs are updated.
WAGO-I/O-SYSTEM 750 ETHERNET TCP/IP