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T7264

U-Interface 2B1Q Transceiver

Agere -> LSI Corporation 

Data Sheet

April 1998

T7264 U-Interface 2B1Q Transceiver

K2 Interface Description (continued)

Table 13. DC Octet (Overview)

Octet

DC

Octet # DO/DI

8

DI

Bit 1

ccrc

Bit 2

istp

Bit 3

lpbk

Bit 4

afrst

Bit 5

ldea

Bit 6

1

Bit 7

sksi

Bit 8

xpcy

Table 14. DC Octet (Functions)

Octet

DC

DC

DC

DC

DC

DC

DC

DC

Bit #

1

2

3

4

5

6

7

8

Symbol

Name/Function

ccrc Corrupt Cyclic Redundancy Check. This bit is used to corrupt the crc information

transmitted by the transceiver to the U-interface.

0—Corrupt crc generation as long as bit is low.

1—Generate correct crc (normal).

istp Initiate Start-Up. This bit is used to notify the transceiver of an activation request.

Should be set to a 1 during loopback. If xact = 1, istp is ignored; if xact = 0:

0—Initiate start-up (activation request).

1—Reset state (transceiver inactive).

lpbk Local Loopback.

0—Loopback.

1—Normal.

Loop back the complete 160 kbits/s U-interface bit stream at the analog output. Loop-

back turns off echo canceler and reconfigures the descrambler. Device should be re-

set and line disconnected before loopback test; istp should be set to a 1 during

loopback.

afrst Adaptive Filter Reset.

0—Normal.

1—Reset.

2B+D and UM set equal to 1 on DO. Reset halts loop transmission and clears the

transceiver's adaptive filter coefficients, overriding all other transceiver control sig-

nals. This provides the same functionality as the RESET pin on the T7264, except F

to MTC synchronization (LT) is not lost.

ldea Local Deactivation.

0 — Normal.

1 — Deactivate. DO 2B+D and UM set equal to 1.

Upon receiving ldea = 1 from the system device, the transceiver will save adaptive fil-

ter coefficients. In the LT, the device sends three or four U superframes of dea = 0,

then ceases transmission and enters the idle state. In the NT, the device deactivates

upon signal loss and enters the idle state. In the NT, ldea should be set before the loss

of signal (on second dea = 0) and held until xact goes low for proper deactivation.

— Reserved. For normal operation, this bit must be set to 1.

sksi System-to-K2. This bit may be set high or low without affecting the state of the trans-

ceiver. sksi is reflected back from the T7264 across the K2 interface by means of the

rsksi bit.

xpcy

Transparency.

0—Transparent 2B+D.

1—LT mode 2B+D = 0 transmitted across the U-interface.

1—NT mode 2B+D = 1 transmitted across the U-interface.

This bit only affects the data transmitted on the U-interface. The U-to-K2 interface al-

ways remains transparent after start-up.

Lucent Technologies Inc.

19

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