BT8376EPF datasheet(114/323 Pages) CONEXANT

114 / 323 page

2.0 Circuit Description

Bt8370/8375/8376

2.11 Loopbacks

Fully Integrated T1/E1 Framer and Line Interface

2-86

Conexant

N8370DSE

2.11 Loopbacks

Bt8370/8375/8376 provides a complete set of loopbacks for diagnostics,

maintenance, and troubleshooting.

2.11.1 Remote Line Loopback

The remote 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. If receive jitter attenuator is also enabled, RJAT is placed in the line

loopback path. TJAT, if enabled, is not present in the line loopback path.

2.11.2 Remote Payload Loopback

The remote payload loopback loops all DS0 channels from the RCVR input to the

XMTR output. Loopback payload retains time slot integrity, such that numbered

time slots from each receive frame are transferred to same numbered time slots in

the transmit frame. Transmit overhead bits—F-bits in T1 mode or TS0 in E1

mode—are supplied by the transmit frame formatter or by the TSB, depending on

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 does not

override by transmit per-channel remote loopback selection (TLOOP bit in

TPCn).

2.11.3 Remote Per-Channel Loopbacks

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].

BT8376EPF Datasheet(PDF) 114 Page - Synaptics Incorporated.