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4. Troubleshooting (DeviceNet)

4.1.3 Procedures for Examining Possible Causes

4.1.3.1 Connection 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.

Te s t e r

Measure resistance between signal wires with tester.

Ω

Blue (CAN L)Red (CAN H)

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

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Epson EM07ZS1647F Specifiche Pagina 110