T7630 datasheet(49/210 Pages) AGERE

49 / 210 page

Lucent Technologies Inc.

Preliminary Data Sheet

October 2000

T7630 Dual T1/E1 5.0 V Short-Haul Terminator (Terminator-II)

Lucent Technologies Inc.

LIU-Framer Interface (continued)

Table 17 shows the encoding of a string of zeros using B8ZS. B8ZS is recommended when ESF format is used. V

represents a violation of the bipolar rule, and B represents an inserted pulse conforming to the AMI rule.

Table 17. DS1 B8ZS Encoding

CEPT: High-Density Bipolar of Order 3 (HDB3)

The line code used for CEPT is described in ITU Rec. G.703 Section 6.1 as high-density bipolar of order 3 (HDB3).

HDB3 uses a substitution code that acts on strings of four zeros. The substitute HDB3 codes are 000V and B00V,

where V represents a violation of the bipolar rule and B represents an inserted pulse conforming to the AMI rule

defined in ITU Rec. G.701, item 9004. The choice of the B00V or 000V is made so that the number of B pulses

between consecutive V pulses is odd. In other words, successive V pulses are of alternate polarity so that no direct

current (dc) component is introduced. The substitute codes follow each other if the string of zeros continues. The

choice of the first substitute code is arbitrary. A line code error consists of two pulses of the same polarity that is not

defined as one of the two substitute codes. Excessive zeros consist of any zero string length greater than four con-

tiguous zeros. Both excessive zeros and coding violations are indicated as bipolar violations. An example is shown

in Table 18.

Table 18. ITU HDB3 Coding

Frame Formats

The supported North American T1 framing formats are superframe (D4,

SLC-96, and digital data service-DDS)

and extended superframe (ESF). The device can be programmed to support the ITU-CEPT-E1 basic format with

and without CRC-4 multiframe formatting. This section describes these framing formats.

T1 Framing Structures

T1 is a digital transmission system which multiplexes twenty-four 64 kbits/s time slots (DS0) onto a serial link. The

T1 system is the lowest level of hierarchy on the North American T-carrier system, as shown in Figure 20.

Table 19. T-Carrier Hierarchy

Bit Positions

123

456

—

345

678

Before B8ZS

000

0010

100

000

After B8ZS

0B0

B0V

Input Bit Stream

1011

0000

HDB3-coded Data

1011

000V

B00V

HDB3-coded Levels

–0+–

000–

000+

–00–

+00+

–00–

HDB3 with 5 Double BPVs

–0+–

–000

+00+

0– – –

+00+

–00–

1-BPV

3-BPV

5-BPV

T Carrier

DS0 Channels

Bit Rate (Mbits/s)

Digital Signal Level

1.544

DS1

T1-C

3.152

DS1C

6.312

DS2

672

44.736

DS3

4032

274.176

DS4

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