Rockwell Automation 1788-CNCHKR ControlNet NetChecker User Manual - Manual (Page 17)

ControlNet NetChecker 17
Rockwell Automation Publication 1788-UM001B-EN-P - August 2012
Slow Edges is generally reported when a weak input signal with poor (slow) rising/falling edges is
identified. This may occur with signals received from remote stations on long networks with a
large number of nodes. In this case, Slow Edges detection is not influenced by the threshold
setting on SW3.
Make sure that the cable length versus number of nodes meets the ControlNet specification.
Check for possible high signal attenuation caused by inadequate coaxial media used for the trunk
cable or segments. High resistance at the contact points of the BNC connectors on the trunk
cable may add abnormal signal attenuation. A small amount of Slow Edges can be tolerated on
long networks provided that the bargraph shows that the minimum level is correct.
Slow Edges may also be reported along with Poor Signal Quality and Illegal Framing in the case
of strong impedance mismatches on the network causing a high amount of distortion. In this
situation, the threshold setting may influence the recurrence of the faults.
Reporting Examples
The figures below show examples of the reporting by the NetChecker.
Check the Signal Level by Using the Threshold Setting
In the example at left, the NetChecker reports no fault at the highest sensitivity (low threshold).
The network is OK at the point of test. The status indicator Node On Line is green because
there is a node transmitting at address 07.
The example at right shows faults reported at High Threshold. Generally, this indicates a high
level of reflections on the network: the network may not be correctly terminated, is accidentally
open or shorted, or there is bad contact in a BNC connector. The status indicator Node On Line
is Off because there is no node at address 11.