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T7264

U-Interface 2B1Q Transceiver

Agere -> LSI Corporation 

Data Sheet

April 1998

T7264 U-Interface 2B1Q Transceiver

U-Interface Description

Data is transmitted over the U-interface in 240-bit groups called U frames. Each U frame consists of an 18-bit syn-

chronization word (ISW or SW), 12 blocks of 2B+D data (216 bits), and six overhead bits (M). A U-interface super-

frame consists of eight U frames grouped together. The beginning of a U superframe is indicated by the inverted

sync word (ISW). The six overhead bits from each of the eight U frames, when taken together, form the 48 M bits.

The following diagram shows how U frames, superframes, and M bits are mapped.

ISW[18]

U1

U2

U-FRAME SPAN = 1.5 ms

(2B+D) X 12 [216 bits]

M[6]

U-SUPERFRAME SPAN = 12 ms

U3

U4

U5

U6

U7

U8

U-INTERFACE M BITS [48]

Figure 12. U-Interface Frame and Superframe

5-5171

Of the 48 M bits, 24 bits form the embedded operations channel (eoc) for sending messages from the LT to the NT

and responses from the NT to the LT. There are two eoc messages per superframe with 12 bits per eoc message

(eoc1 and eoc2). Another 12 bits serve as control and status bits (UCS). The last 12 bits form the cyclic redun-

dancy check (crc) which is calculated over the 2B+D data and the M4 bits of the previous superframe. Figure 13

shows the different groups of bits in the superframe.

BIT #

1—18

19—234

235

FRAME #

Sync

12(2B+D)

M1

1

ISW

2

3

4

SW

2B+D

5

6

7

8

236

M2

eoc1

eoc2

237

238

239

240

M3

M4

M5

M6

CONTROL & STATUS (UCS)

crc

Figure 13. U-Interface Superframe Bit Groups

5-5172

Lucent Technologies Inc.

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