BT8376EPF datasheet(145/323 Pages) CONEXANT

145 / 323 page

Bt8370/8375/8376

3.0 Registers

Fully Integrated T1/E1 Framer and Line Interface

3.6 Primary Control and Status Registers

N8370DSE

Conexant

3-27

3.6 Primary Control and Status Registers

Unused bits indicated by a dash (—) are reserved and should be written to 0. Writing to reserved bits has no

effect.

014—Loopback Configuration Register (LOOP)

PLOOP

Enable Remote Payload Loopback—Payload from the receiver replaces the payload on

transmitter output. The loopback payload retains the time slot and frame integrity, so

numbered time slots from each receive frame transfer 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 the transmit system bus, according to TFRM [addr 072]

settings. Existing transmit frame alignment and clock timing is not altered by PLOOP

activation or deactivation, allowing system operation with independent receive and transmit

timing. Controlled frame slips are performed in the payload loopback path if the 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 channel

loopbacks [TPCn; addr 100–11F] must be used to implement payload loopbacks when

transparent or forced signaling is desired. PLOOP does not override by the transmit

per-channel selections (TPCn).

0 = no loopback

1 = payload loopback

LLOOP

Enable Remote Line Loopback—Dual-rail unipolar data from RLIU (or RJAT) is internally

connected to TLIU. The recovered clock from RPLL (or JCLK from RJAT) is internally

connected to the transmitter. Loopback data retains BPV transparency. Data input from the

transmit system bus continues to pass through the transmitter, but is ignored at ZCS encoder

outputs. Data passage from RLIU block to RSB block is unaffected. LLOOP and FLOOP can

be simultaneously active to support line and network loopbacks simultaneously.

0 = no loopback

1 = line loopback

FLOOP

Enable Local Framer Loopback—Dual-rail unipolar data from the transmit ZCS encoder is

internally connected to receive ZCS decoder inputs. The signals from the transmit clock input

(TCKI) is internally connected to the receive clock output (RCKO). Externally applied data on

RTIP/RRING inputs is ignored. XTIP/XRING output data is unaffected. If RCKO is selected

as the TCKI clock source [CMUX; addr 01A], an alternate transmit clock source must be

provided when this loopback is activated. Possible configurations include selecting the TCKI

pin or CLADO as the transmit clock source, or programming the JAT in the transmit direction

and setting JFREE to enable the free-running 10 MHz reference [JAT_CR register; addr 002].

0 = no loopback

1 = framer loopback

————

PLOOP

LLOOP

FLOOP

ALOOP

BT8376EPF Datasheet(PDF) 145 Page - Synaptics Incorporated.

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