Epson RC90 Manual page 316

4. Troubleshooting (PROFIBUS DP)
♦ Causes of Error
Possible Cause
 Disconnected
terminating resistors
 Cable disconnection
 Disconnected
connector
 Disconnected signal
wire
 Loose connector
 Loose signal wire
 Noise
(external cause)
 Broken unit
 No cause is
identified.
304
Examination Method
(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.
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
Signal Wire.
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
4.2.3.3 Noise Intrusion.
Replace the trouble unit with a
new one.
→Verify whether the problem is
fixed.
Identify the trouble point by
dividing the network.
→For details, refer to the section
4.2.3.4 Broken Unit
Examination.
RC700 / RC90 Option Fieldbus I/O Rev.14
Countermeasure
Fix the 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.
Connect the connectors
and signal wires again.
Take countermeasures
against noise.
Replace the unit with a
new one.