CX28394/28395/28398
2.0 Circuit Description
Quad/x16/Octal—T1/E1/J1 Framers
2.6 Loopbacks
2.6 Loopbacks
The device provides a complete set of loopbacks for diagnostics, maintenance,
and troubleshooting for each framer. All loopbacks perform clock and data
switching, if necessary.
2.6.1 Remote Line Loopback
The line loopback loops the RCVR inputs to the XMTR outputs. The loopback
provides BPV transparency and the ability to override the looped data with AIS.
The RCVR data path is not affected by the activation of this loopback. Remote
line loopback is activated by setting the Remote Line Loopback (LLOOP) bit in
the Loopback Configuration register [LOOP; addr 014]. It is possible to operate
the remote line loopback simultaneously with the local framer loopback.
2.6.2 Remote Payload Loopback
The payload loopback loops all DS0 channels from the RCVR input to the XMTR
output. Payload loopback retains time slot integrity, so that numbered time slots
from each receive frame are transferred to the same numbered time slots in the
transmit frame. Transmit overhead bits—F-bits in T1 mode or TS0 in E1
mode—are supplied by transmit frame formatter or by TSB according to TFRM
[addr 072] settings. Existing transmit frame alignment and clock timing are not
altered by [PLOOP; addr 014] activation or deactivation, allowing system
operation with independent receive and transmit timing. Controlled frame slips
are performed in the payload loopback path if receive and transmit clocks are
asynchronous, although these slips are not reported to the processor as slip buffer
errors. Multiframe integrity is not maintained during PLOOP; therefore, DS0 and
signaling channel loopbacks [TPCn; addr 100–11F] must be used to implement
payload loopback if transparent or forced signaling is desired. PLOOP overrides
transmit per-channel remote loopback selection (TLOOP bit in TPCn).
2.6.3 Remote Per-Channel Loopback
The remote per-channel loopback loops the RCVR input DS0 channel to the
XMTR output DS0 channel. The remote per-channel loopback is activated by
setting TLOOP in the Transmit Per-Channel Control register [TPC0 to TPC31;
addr 100 to 11F].
100054E
Conexant
2-59
CONEXANT [ CONEXANT SYSTEMS, INC ]
