Chapter 6 System Testing Gen 3 Site Controller System Manual
Remotely Looping Back the T1 Site Controller for BER Testing
6-20 68P80801E30-A 5/1/2002
Remotely Looping Back the T1 Site
Controller for BER Testing
SR7.0 or later Boot ROM software provides T1 loop-back features not
available in previous releases. System operators should be aware that
previous system releases did not support loop-back when the site controller
was operating from boot ROMs. With SR7.0 or later boot ROM flash loads,
the site controller no longer resets after it has been put into loop-back . The
system operator must send the appropriate loop-down commands to end the
loop-back.
Loop-back capability has always existed for the site controller when it
operates under software downloaded from the OMC. Performing a
loop-back test breaks the data links between the MSO and the EBTS.
The site controller downloaded software includes a timer with a default
value of one hour. When the links have been broken for one hour, this timer
initiates a site controller reset and clears the loop-back. The value of this
timer can be changed to run a longer loop-back test. This timer does not
effect loop-backs when site controller is operating under Boot ROM
software.
Two Types of T1 Loop-Back
Line Loop-Back
Line Loop-Back connects the received data from the network to the line
driver. The data passes through the site controller unchanged. Framing
errors, CRC errors, bipolar violations, and data errors pass back to the
network as they were received.
Payload Loop-Back
Payload Loop-Back takes data received from the line and loops it back
through the framer chip. This process loops back the data on the 24 DS0s,
but generates new framing bits and CRC. The loop-back removes bipolar
violations. A new data stream is created for the Facility Data Link.
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