4. Troubleshooting (DeviceNet)
4.1.3 Procedures for Examining Possible Causes
4.1.3.1Connection Problem (Disconnected Terminating Resistors, Cable Disconnection, Disconnected Connector, Disconnected Signal Wire)
(1)Ensure that two terminating resistors are connected to both ends of the network.
(2)Turn OFF the communications power supply.
(3)Measure resistance between CAN_H and CAN_L wires of the absent slave using the tester.
Tester
Measure resistance between signal wires with tester.
Ω
Red (CAN H) | Blue (CAN L) |
Resistance | Determination |
0 Ω | Shot circuit |
Under 50 Ω | Three or more terminating resistors on one network |
50 to 70 Ω | Normal |
70 to 120 Ω | Error (cable disconnection or disconnected signal wire on the |
| trunk line) |
Over 120 Ω | Error (cable disconnection or disconnected signal wire on drop |
| line or trunk line → Both CAN_H and CAN_L) |
(4)How to find the trouble point:
-Remove the terminating resistor on one end of the network.
(The resistance at the point where the terminating resistor is connected is 120 Ω.)
-Measure resistance at branch taps of all units.
-The trouble point is where resistance changes from 120 Ω.
-After finding the trouble point, verify the connector and cable conditions.
98 | Fieldbus I/O Rev.6 |
