Design Installation Guide Owner's manual

Publication DNET-UM072C-EN-P - July 2004
Correct and Prevent Network Problems 5-3
Diagnose Common
Problems
Use the following tips to diagnose and correct some of the most commonly
occurring network problems.
TIP
Most devices have some type of status display, such as
LEDs or alpha-numeric message displays. If any of your
devices display error messages, refer to the documentation
provided by the manufacturer to interpret the error codes.
problem symptom do this
common mode problems • nodes near the end of the trunk line stop
communicating after operating normally
• the network communicates only when the
number of nodes is decreased or the trunk
length is reduced
• properly configured slave devices are not
detected by the scanner
• check communications at the end of the
network
• check common mode voltage
• move nodes from the overloaded section to
the less-overloaded section
• shorten the overall length of the network
cable
• move power supply in the direction of the
overloaded section of the network
• move high-current nodes (e.g., valve banks)
close to the power supply
• add a second power supply
• break the network into 2 separate networks
bus errors • node operates intermittently (drops off
suddenly and unexpectedly)
• LEDs or other displays indicate buss off
errors
• Check that baud rates are set correctly. A
device with an incorrectly set baud rate
affects other nodes when the device
attempts to go online.
• replace the suspected faulty device and
re-check error rates
• check cables for intermittent operation by
shaking, bending or twisting the suspected
cable or connection and checking error rates