Troubleshooting - Novatech Bitronics M87X Series Manual

8.13.2 Troubleshooting

If the Link LED fails to illuminate, this is an indication that there is trouble with the
connection and communication will not proceed without solving the problem. If a copper
connection is used between the M87x and the hub/switch, check the following items:
Verify that the connectors are fully engaged on each end.

Verify that the cable used is a "straight-through" cable connected to a "normal" port.
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Alternatively, a "cross-over" cable could be connected to an "uplink" port (this could
later cause confusion and is not recommended).
Verify that both the M87x and hub/switch are powered.

Try another cable.
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If a long CAT-5 cable is used, verify that is has never been kinked. Kinking can cause
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internal discontinuities in the cable.
Try removing the jumpers (the factory default).
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If a fiber-optic connection is used:
Verify that the hub/switch matches the Ethernet card port. A 100BASE-FX port will
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NEVER inter-operate with the 10BASE-FL port (fiber auto-negotiation does not exist).
Try swapping the transmit and receive connector on one end.

Verify that the hub/switch uses the proper optical wavelength (10BASE-FL should be

820 nm and 100BASE-FX should be 1300 nm). Note that the Ethernet card may take
up to 12 seconds before it enables the 10BASE-FL transmitter, but it leaves the
transmitter on for about 5 seconds before giving up.
If a copper connection is used to an off-board fiber converter:
Verify that the LINK LED on the converter is lit on at least one side. Both sides need to

be lit for a valid connection to be established.
At least one brand of converters will not output an optical idle unless it receives a

forced 10 Mb copper link pulse (for some reason, auto-negotiation pulses confuse it).
Some hubs/switches will not output an optical idle unless they receive an optical idle.
This then inhibits the converter from outputting a copper link pulse enabling the M87x
to link. In this condition, no device completes the link. To get around this condition,
some device needs to start a valid signal to "get the ball rolling". The M87x Ethernet
card can be manually configured via jumpers for either "Force 10BASE-T half duplex"
or "Force 10BASE-T full duplex" which guarantees that the converter will see a valid 10
Mb copper link pulse. This then causes it to output an optical idle which the hub/switch
turns around to an output optical idle which the converter then turns into a copper idle
signal which then allows the Ethernet card to link and everything works. See the above
section for the proper jumper settings. This method even works if a fiber-to-copper
converter is also used at the hub end (i.e., using copper Ethernet interfaces on both
ends with a fiber-optic cable between them).
Follow the suggestions for the all copper and all fiber system troubleshooting.

If both the LINK LED and the RX LED are both constantly on and the hub/switch indicates
that it is not transmitting, the system is in the "false link" state. One known cause is using
a non-auto negotiating 100BASE-TX hub/switch and setting the jumpers for "force
10BASE-T" mode. Moving the jumpers back to the factory default locations will cure this
problem.
ML0021 August 15, 2018
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