4. Troubleshooting (PROFIBUS DP)
RC700 / RC90 Option Fieldbus I/O Rev.14 299
♦ Causes of Error
terminating resistors
Cable disconnection
Disconnected
connector
Disconnected signal
wire
(1) Check that terminating
resistors are connected to
both ends of the network.
(2) Measure resistance between
signal wires with device
power supply OFF.
→ Normal: 100 to 120 Ω
Measuring point: Connection
of the trouble unit
For details, refer to the section
4.2.3.1 Connection Problem.
How to find the trouble
point:
Remove the terminating
resistor on one end of the
network. The trouble point
is where resistance
changes from 220 Ω.
Loose signal wire
Check for the connection of
connectors and signal wires.
→ The connectors and signal
wires should be firmly connected.
Checkpoint: all stations and all
branch taps
For details, refer to the section
4.2.3.2 Loose Connector and
and signal wires again.
(external cause)
Check the noise intrusion via the
following paths (1) to (3).
(1) Noise via shield
(2) Induced noise via
communication cable
(3) Device power supply
→ For details, refer to the section
against noise.
Replace the trouble unit with a
new one.
→ Verify whether the problem is
new one.
identified.
Identify the trouble point by
dividing the network.
→ For details, refer to the section
4.2.3.4 Broken Unit