DEFINITY Enterprise Communications Server Release 7
Maintenance for R7r
555-230-126 Issue 4
June 1999
Maintenance Object Repair Procedures
9-1704TDM-BUS (TDM Bus)
9
TDM Bus Fault Detection and Isolation
TDM Bus are usually caused by one of the following:
■A defective circuit pack connected to the backplane
■Bent pins on the backp lane
■Defective bus cab les or terminators
It is possible that a circuit pack can cause a TDM Bus fault and still exhibit
trouble-free operation. For example, insertions of a ny circuit pack into a slot wi th
TDM Bus terminations may bend the bac kplane pins and shor t two leads
together. Since the TDM Bus is a shared resource, id entification of the cause of a
TDM Bus fault can be difficult. If a TDM Bus problem is suspected , run the test
tdm P command. If any of the resulting tests fail, you must perform a manual
TDM Bus isolation procedure to identify the cause of the problem.
!WARNING:

Since the TDM Bus fault isolation procedu re involves removing circuit pac ks

and possibly d isconnecting entire c arriers, the procedure is extremely

destructive to the port network that contains the TDM Bus being tested . If

possible, arrange to p erform this proced ure at a time when traffic is

minimal.

As circuit pack s are removed or entire carriers are disco nnected, any active c alls
terminating on those circui t packs or carriers will b e dropped. If you have any
hints about a particul ar circuit pack that may b e causing the TDM Bus problem
investigate those before per forming this proced ure (for example, look at any
circuit packs th at were inserted into the PN just before the TDM bus prob lem
appeared.
When straightening or replacin g backplane p ins in a carrier that contains a
CFY1B Current Limiter, power to the

cabinet

must be removed. When
straightening or replac ing backplan e pins in a carrier that does NOT contai n a
CFY1B Current Limiter, power to that

carrier

must be shut off. Failure to follow this
procedure may result in da mage to circuit pac ks and power supp lies, and can
be hazardous to the technic ian.
NOTE:
Maintenance software requires TN748 or TN420 Tone Detector circuit pac k
to test the TDM Bus. Before starting these proced ures, make sure that one
of these is installed in the port network being investigated .
Procedure 1
This procedure is an attempt to isolate the TDM Bus fault to circuit pac ks that are
essential to the system operation. For each of the following circuit pack s in the
port network where the TDM Bus fault appears, p erform Procedure 1.