Siemens SIMATIC NET PROFIBUS manual Troubleshooting, Fault indicated on the system LED

5 LED Indicators and Troubleshooting 5.2 Troubleshooting

5.2 Troubleshooting

This chapter helps you to localize faults after they have been indicated (by LEDs or signal contacts). Please also refer to the description of the LED indicators in 5.1, p. 25.

Fault indicated on the system LED

See description of the LED indicators in 5.1, p. 25.

Fault indicated on CH1

Check the following:

the DIL switch S0 is in Position 1 if the OLM is connected to the electrical star segment of a star topology (see Chap. 3.2 ”Star topology“, p. 12).

the fault is still displayed after removal of the RS485 connector.

Still displayed: Device is defective*.

Replace the OLM.

No longer displayed: The fault lies in the RS485 bus segment.

Check

– all RS485 connectors as described in 4.4.3 ”Connecting the electrical RS 485 bus lines“, p. 22

– the structure and shielding of the RS485 bus segment

– the RS485 bus segment using a PROFIBUS bus monitor

– the configuration of all bus subscribers.

* This is not the case if the monomaster of a PROFIBUS network is connected to the RS485 bus segment which is to be examined. Replace the OLM concerned with another OLM from the network, and then carry out the test described above.

If the OLM still malfunctions when connected elsewhere, the device is defective. Replace the OLM.

If the OLM does not malfunction elsewhere, the fault lies in the RS485 bus segment. Carry out the measures described above.

Fault indicated on CH2 / CH3

1. Check the following:

optically only modules of the same type are connected together (see 3, ”Network topologies“, p. 9)

the optical fiber has been approved for the module type being used, and that it does not exceed the permitted length (see Table 1, p. 6)

the optical ports, which are connected via optical fibers, have been set to the same operating mode (see 4.3, ”Setting compatibility, operating mode and transmitting power“, p. 17)

the settings given in 4.4.1, ”Connecting the optical lines“ (p. 20) have been observed when connecting and laying the optical bus lines.

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