BT8376EPF datasheet(93/323 Pages) CONEXANT

93 / 323 page

Bt8370/8375/8376

2.0 Circuit Description

Fully Integrated T1/E1 Framer and Line Interface

2.8 Transmitter

N8370DSE

Conexant

2-65

Fs and MFAS errors are controlled by the TMERR bit in the TERROR

by logically inverting the next multiframe bit transmitted.

CAS Multiframe (MAS) errors are controlled by the TSERR bit in the

TERROR register. TSERR commands a single MAS pattern error by logically

inverting the first MAS bit transmitted.

2.8.7 In-Band Loopback Code Generator

The in-band loopback code generator circuitry overwrites the transmit data with

in-band codes of configurable value and length. These codes are sequences with

periods of 1 to 7 bits and may, in some applications, overwrite the framing bit.

The Transmit Inband Loopback Code Configuration register [TLB; addr 077]

controls the functions required for this operation.

A loopback code is generated in the transmit data stream by writing the

loopback code to the Transmit Inband Loopback Code Pattern register [LBP; addr

078], and then by setting the Start Inband Loopback (LBSTART) and Loopback

Length (LB_LEN) bits in the Transmit Inband Loopback Code Configuration

to overwrite framing bits using the UNFRAMED bit. The LB_LEN provides

loopback code pattern lengths of 4 to 7 bits. Patterns of 2 or 3 bits can be achieved

by repeating the pattern in 4- or 6-bit modes, respectively. Framed or unframed all

1s or all 0s can also be achieved by setting the pattern to all 0s or all 1s. The

in-band loopback code generator is applicable only to T1 mode.

2.8.8 ZCS Encoder

The ZCS encoder encodes the single rail clock and data (unipolar) into dual rail

data (bipolar). The Transmit Zero Code Suppression Bits (TZCS[1,0]) in the

Transmitter Configuration register [TCR1; addr 071] selects ZCS and Pulse

Density Violation (PDV) enforcement options for XTIP/XRING and

TPOSO/TNEGO output pins. TZCS supports the following: Alternate Mark

Inversion (AMI), High Density Bipolar of order 3 (HDB3), Bipolar with 8 Zero

Suppression (B8ZS), Pulse Density Violation (PDV), Unassigned Mux Code

(UMC), and Bipolar with 7 Zero Suppression (B7ZS).

NOTE:

ZCS encoding, which alters data content, is performed prior to the CRC

calculation so the outgoing CRC will always be correct.

The AMI line code requires at least 12.5% average 1s density and no more

than 15 consecutive 0s. A 1 is encoded as either a positive or negative pulse; a 0 is

the absence of a pulse. Two consecutive pulses of the same polarity are referred to

as a Bipolar Violation (BPV).

BT8376EPF Datasheet(PDF) 93 Page - Synaptics Incorporated.

BT8376EPF Datasheet(HTML) 93 Page - Synaptics Incorporated.

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