Paradise Datacom P300 Series, Руководство по установке и эксплуатации

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P300H P300 Series Modem Installation and Operating Handbook Page 132
When the processor reads the BER counters once per second (errors, number of bits etc), it has to freeze the counts in order to
read the results accurately (in case the counters increment whilst being read). This reading of the counters takes less than 0.1% of
the time, but does mean that the BERT is `blind` for a small proportion of the time and some individual errors may not be counted.
However the BER is 100% accurate because as well as counting Errors, the BERT also counts PRBS bits received, and calculates
the BER as <Errors> / <Count of bits received> (ie both are in proportion). This would
not be the case if we did not count the bits
received, and simply assumed that the error rate was <Errors> / (<Time> x <Rate>).
This may not sit comfortably on first reading, but you are probably happy with the concept that a PRBS multiplexed in with the main
data channel at say 5% of the main data rate will provide the same BER reading as for the main data channel itself. You would
probably agree that the result would be no different if the PRBS content was dropped to say 4% of the main data channel, implying
that reducing the bits available to measure the BER by 20% will have no effect on the validity of the BER reading. The argument for
the Internal BERT is no different, >99.9% of the bits available for BER measurement are used, with the other <0.1% lost as the
processor reads the hardware registers.
6.17 SETUP MENU
See Setup - Initial Configuration Menu on page 56
6.18 ACTION MENU
Action: 1=Buffer Centre
2=Slip counter reset 3=1:1 Give away control
Action Menu
The options on this menu are fairly self explanatory, however for completeness:
ÞËÚÚÛÎ
ÝÛÒÌÎÛ
Forces the Rx buffer to re-centre, and will cause a burst of errors. This is
automatically performed when the Rx traffic goes from fail to OK if the option
under
ÝØßÒÙÛô ËÍÛÎóÑÐÌô ÑÐÛÎßÌ×ÑÒô ßÝÌ×ÑÒÍô ÞËÚÚÛÎ ßËÌÑ ÝÛÒÌÎÛ
is enabled.
ÍÔ×Ð ÝÑËÒÌ
ÎÛÍÛÌ
This resets the counts of underflows and overflows on the
ͬ¿¬«-
status
screens
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When two Modem's are configured as a 1:1 pair, this can be selected on the
on-line unit, to handover control to the off-line unit.