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B-6
MAX Administration Guide
Diagnostic Parameters and Commands
Using diagnostics-related VT100 commands
UnCorrupt CRC
Rq Corrupt CRC
UnRq Corrupt CRC
Clr NEBE
Clr FEBE
To execute one of the commands, select it and press Enter.
Note:
Maintenance functions supported by the BRI/LT driver use the BRI-U interface’s
Embedded Operations Channel (EOC). The EOC transfers data from the exchange to the
terminal side and vice versa without occupying either the B or the D channel. The EOC is used
to transmit diagnostic function and signaling information, (obtaining the block errors in close
to real time or performing line diagnostics such as loopback or corrupt CRC, for example.)
The EOC monitor commands are sent in the M1, M2, and M3 bits of the U superframe. (For
more information about usage of the M1, M2, and M3 bits of the superframe, see ANSI
T1-601, from ANSI 1991.
The remote U-interface/echo canceller provides internal counters for far-end and near-end
block errors. A Near-End Block Error (NEBE) indicates that the error has been detected in the
receive direction. A Far-End Block Error (FEBE) identifies errors in the transmission
direction.
You can use the block error counters to monitor transmission quality at the U interface. A
block error is detected each time the calculated checksum of the received data does not
correspond to the control checksum transmitted in the successive superframe. One block error
indicates that one U-superframe has not been transmitted correctly. The block error count does
not provide information regarding the number of bit errors in the U superframe, but states only
that the CRC failed in that superframe. About every 4 seconds, a daemon running in the MAX
unit obtains the remote block error counter values and displays their cumulative value in the
block- error status screens.
The block-error totals are obtained from the remote TA. These cumulative totals are reset when
you clear the block-error buffer(s) from the Line diagnostics submenu, or when you restart the
MAX unit. The totals reset to zero when they reach 65535.
Note:
See the Block Error status display in the BRI/LT status window of the block-error
information displayed.
Line LoopBack
The Line LoopBack command puts the line into loopback mode. When you select the Line
LoopBack command and press Enter, the following screen appears:
Line LoopBack
0=ESC
1=Line X LB
Select 1 to execute the loopback command. Test frames are sent continuously in the D channel
until the command is cancelled. The transmitted frames are each 24 bytes long. The frames
differ in content and should cover every possible bit pattern.
Note:
Only one loopback test can be performed at a time on the same line. If another user
attempts to invoke the loopback command for a line that is already in loopback mode, the
following error message appears: