Loopback Plugs For Testing Interfaces - Allied Telesis AT-AR020 PRI E1/T1 Hardware Reference Manual

Hardware Reference
C613-03023-00 REV N

Loopback Plugs for Testing Interfaces

Loopback plugs are used in conjunction with the Test Facility in the
AlliedWare operating system to test the physical interfaces on all PICs except
the AT-AR026 and AT-AR027. For more information about the Test Facility, see
"Test Facility" on page
Operating System Software Reference.
A loopback plug connects the output pins on the interface to the input pins so
that any data transmitted over the interface is looped back (hence loopback
plug) and received at the same interface.
On interfaces with control signals, these are also looped back. The data
received on the interface is compared with the data transmitted on the interface
to determine whether or not the interface is functioning correctly. In order to
produce a comprehensive test report for the interface being tested, most tests
performed by the Test Facility require a loopback plug to be inserted.
Synchronous interfaces require an external test device to be used in conjunction
with the Test Facility. Use a loopback test to the local DCE.
BRI S/T interfaces that use an MC145574 transceiver require a loopback plug to
test the BRI interface. To determine which type of transceiver a BRI interface
uses, use the command:
show bri test
Figure 24 shows an example of the output screen from the show bri test
command. The transceiver type is listed in the first line of output.
Figure 24: Example output from the show bri test command
Test switches for BRI instance 0 (MC145574 transceiver):
Number Action
------------------------------------------------------
1 Transceiver B1 GCI Transp Loop ........... no
2 Transceiver B2 GCI Transp Loop ........... no
3 Transceiver 2B+D GCI Transp Loop ......... no
4 Transceiver B1 GCI Non-Transp Loop ....... no
5 Transceiver B2 GCI Non-Transp Loop ....... no
6 Transceiver B1 S/T Transp Loop ........... no
7 Transceiver B2 S/T Transp Loop ........... no
8 Transceiver B1 S/T Non-Transp Loop ....... no
9 Transceiver B2 S/T Non-Transp Loop ....... no
10 Transceiver External S/T Loop ............ no
11 Transceiver 96kHz Test Tone .............. no
12 Transceiver Force Activation ...... ...... no
13 Transceiver Ignore D Channel Procs ....... no
14 Transceiver Map E Channel to GCI ......... no
15 Transceiver GCI Free Run ................. no
BRI S/T interfaces that do not use an MC145574 transceiver, and BRI U
interfaces, do not require loopback plugs. The Test Facility will perform an
internal loopback test on these interfaces. To perform an external loopback test,
an external NT mode device is required. To test NT mode operation on the V2
hardware revision of the AR021(S) PIC, use an external TE device.
43, and the Test Facility chapter of the AlliedWare
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