Verilink PRISM 3030 (34-00208.L) Product Manual - Manual (Page 47)

Diagnostics 37
The unit monitors network loopback commands and activates loops based upon
their reception as described in TR 54016 and T1.403. Refer to Figure 3-20 for a
depiction of the loop modes (See also Figure 4-7 and Figure 4-8 on page 59). The
Diagnostics menu allows for loopback and BERT functions as explained in the
following paragraphs.
T1 Network Loop The looping choices are as follows (note that far loops are not allowed during
BERT).
NONE
Network loop not present.
LOOP FAR
Sends loop codes over the network to the far end unit to force it into a NET LLB.
UNLOOP FAR
Sends unloop codes to the far end unit to remove the loop condition.
NET PLB
The payload loopback selection loops the data back toward the network. Framing,
CRC, and FDL are regenerated and all ones are passed to the DTE ports.
NET LLB
The local loopback selection loops data received from the network back toward the
network. Received data is also passed through to the DTE ports as normal.
NET MLB
Network maintenance loopback loops data at the T1 DTE port back toward the
network (passes network data to DTE and return data to network). This affects
only network channels assigned to the T1 DTE.
Multiplexer
BERT
Pattern
Generator
and
Detector
Framing,
CRC, and FDL
Control
Network
Interface
Tx
Rx
DSX1 T1 DTE Port
Receiver
Driver
TX
RXD
DTE Slot X, Port Y
Receiver
Driver
TXD
RXD
FIFO
FIFO
NET LLB
NOTE: Commanded
loops are initiated by
receipt of the appropriate
loop code from the
network or the far end.
Bidirectional fractional port loop
DTE MLB NET PLB DTE LLB
NET MLB
Figure 3-20 Diagnostics Loop Functions