Design Installation Guide Owner's manual

Publication DNET-UM072C-EN-P - July 2004
5-4 Correct and Prevent Network Problems
bus traffic problems • nodes stop communicating
• device times out
• check scanner configuration to ensure scan
rate is set correctly
− inter-scan/delay scan interval too short
can cause device timeouts
− inter-scan/delay scan interval too long
can reduce system performance and
make inefficient use of available
bandwidth
• check change-of-state devices consuming
excessive bandwidth
• increase production inhibit time or change
these devices to polling, cyclic, or bit strobe
communication
• check for nodes with excessive bandwidth or
a much-higher than average MAX value
bus power 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
• check network power voltage at the node
• check common mode voltage
• check for output devices (e.g., contactors)
powered from the network
• check for interference caused by network
cables routed too closely to high-voltage and
RF lines
• use an oscilloscope to check the power
supply trace for ripple increasing over time
against the baseline
• check cables for intermittent operation by
shaking, bending or twisting the suspected
cable or connection and checking
peak-to-peak voltages
shield voltage problems • nodes operate intermittently
• properly configured slave devices are not
detected by the scanner
• check shield voltage
• check for additional V- or shield wire
connections
• check for loose connections (in particular,
field-attachable connections)
• ensure that only shield and V- wires are
connected together at earth ground and the
power supply
problem symptom do this