Siemens ADVANCE NETWORK COMMUNICATIONS BOARD/DATANET 20005 User Manual download pdf (Page 64)

DataNET Troubleshooting Guiding, Continued

If the ANCB_DN port LED is never green, or intermittently flashes

between green and red, there may be a signal quality problem. Signal

levels should be examined to determine if a particular port has a signal

too large or too small relative to the other ports on the HUB. If a link fails

to connect at all, place the port in a test mode which will cause activity to

occur every ~50 milliseconds instead of every ~5 seconds as on an

unconnected link.

Signal Quality

Problems

To place the unit in a test mode use the CLI commands to take the link

offline (port stop n) and initiate the test mode (test n). At this time, an

oscilloscope may be taken to the site of the slave device and connected

to monitor the signal. The signal received at the slave should be between

~0.75 v p-p and 5 v p-p. A signal smaller than ~0.75 v p-p is generally

not adequate. The impedance matching jumpers can be changed to

correct some signal level issues.

Placing Unit in Test Mode

If the condition of excessive signal loss can not be corrected by jumper

settings, it may indicate inadequate cable properties (i.e. too long or

wrong type of cable).

The port can be taken off test mode and put back to normal operation

with the “test off” and “port start n” commands.

54 • Troubleshooting 2000592-001

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Siemens ADVANCE NETWORK COMMUNICATIONS BOARD/DATANET 20005 User Manual Page 64