BECKHOFF BC7300 - Manual (Page 18)

Basic Principles
BC7300 18
off. The electronics in the Bus Terminals and in the Bus Coupler are
protected to a large measure against damage, but incorrect function and
damage cannot be ruled out if they are plugged in under power.
The occurrence of a fault in the course of operation does not immediately
trigger the display of error codes by the LEDs. The Bus Coupler must be
requested to diagnose the Bus Terminals. The diagnostic request is
generated after switching on.
MODBUS LEDs LED: on off
WD Watchdog is active Watchdog is not yet running
or the watchdog time has elapsed
RX Receive Data
Data is being received
TX Transmit Data
Data is being transmitted
PLC Program running
LED flashes while a boot project is being created
WD
RX
TX
PLC
MODBUS
If a K-Bus error occurs during operation, the procedures for reaction to a K-
Bus error are executed in accordance with the parameterisation. If the K-
Bus error occurs during booting, the slave is not included in the data
exchange.
Fieldbus errors
WD A fieldbus error only occurs when the watchdog (WD) period has elapsed.
The watchdog is preset to 1000 ms. The WD is activated as soon as a
"write" access has been made to the coupler's process data (WD LED
goes on). After this, another "write" command must be sent to the process
data within the set WD time, in order to start the WD from zero again.
Once a WD error has occurred, data communication can only be restarted
by resetting the coupler (see "Coupler Reset", under Diagnostics).
The maximum watchdog time is 65000 ms, and it can be set by rotary
switch or via the KS2000 software.