Appendix E Autopolarity Detection And Correction - Bay Networks 281xSA Using Manual

Appendix E Autopolarity Detection and Correction

893-743-A
All Model 281xSA hub 10BASE-T ports support the automatic polarity
detection and correction function, which detects and automatically corrects for
UTP receive data wire-pair signal inversions. If any receive data wire-pair is
mistakenly reversed in the punchdown block during cable installation, the
Model 281xSA hub port internally corrects for the miswiring and the data path
operates correctly.
The Model 281xSA hub ports monitor the polarity of the receive data wire-pair
only during the power-up sequence or while the Model 281xSA hub port has no
link status (Link LED OFF). While a port is being monitored, two conditions
may occur:
If the port receives one normal data packet (no inversion), wire polarity
is considered good and the monitoring for that port stops until either the
power-up sequence or no link status occurs.
If the port receives either two consecutive inverted data packets or six
consecutive inverted link test pulses, the automatic polarity correction
function is enabled to internally correct for the receive data wire-pair
inversion. Monitoring stops until either the power-up sequence or no link
status occurs.
Because the algorithm monitors both data packets and link test pulses, the
automatic polarity correction is enabled even if no data is present on the link
segment. There is no indication on the Model 281xSA hub that the wires are
reversed, because no user intervention is required to correct this wiring error.
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