5. Troubleshooting
5-44
May
2003
9000-A2-GB33-20
Latching Loopback (9623, 9626)
A latching loopback is a network-initiated DSU Loopback. Once a DSU Loopback
is started, the
iMarc unit remains in loopback until it receives the loopback-release
sequence from the network.
The latching loopback code is a control sequence (as opposed to a bipolar
violation sequence); therefore, user data may cause the
iMarc unit to activate the
loopback.
Main Menu
→
Configuration
→
Network
→
Physical
Disable the DSU Latching Loopback configuration option to stop the latching
loopback when the network did not command the test.
Send 511 (9623, 9626)
This test sends the 511 test pattern over the selected interface. The 511 test
pattern is a pseudo-random bit sequence (PRBS) that is 511 bits long (on the data
ports only). This is a PRBS 2
9
–1 test.
Main Menu
→
Test
→
[Network Physical Tests/Data Port Physical Tests]
→
Send 511
When sending or monitoring a 511 test pattern using an external loopback
connector on the network or DTE port, you must follow the sequence below for
these tests to run correctly.
Procedure
To send a 511 test pattern using an external loopback connector:
1. Remove the network cable so that a No Signal (NS) condition occurs.
2. Start the Send Pattern test.
3. Place the loopback cable on the network or DTE port interface.
4. Start the Monitor 511 test.