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Cisco WAN Switching Modules

Field Notice: BCC-3 External Clock - Bad Clock Path Error


June 17, 1997



Problem Description

The BCC-3 LM-2 back card causes a "bad clock path error" for the external clock when the DB15 connector is used for T1/E1 lines.

The BCC-3 back card, LM2, had a jumper option not configured correctly for the external clock input. The issue is related to grounding the shield for the BNC connections. So when the external clock from the DB15 (port 1) is received, one of its differential signals gets grounded causing reflections resulting in the "bad clock path" error.

Products Affected

BPX, BCC-3 LM2

BCC-3 LM2 revision A and B.

Note:?New revision B cards that we are shipping already have modifications on it. Look for the label that reads d97-827

Problem Resolution

BCC-3 LM2 revision C.

Release the RCN-Engineering Change for correcting the jumper option. The fix has been tested in the lab. Testing was completed for up to 600+ feet cable.

Use the BNC connectors for E1 or T1 clocks for testing. These should work fine.

Current LM2 cards will work for up to 40 feet cables. If this is workable for test purposes, this workaround can be used.

For More Information

If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods: