XRT73LC00 datasheet(38/53 Pages) EXAR

38 / 53 page

XRT73LC00

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E3/DS3/STS-1 LINE INTERFACE UNIT

REV. P1.0.1

PRELIMINARY

If the XRT73LC00 is operating in the HOST Mode,

the state of ALOS can be polled or monitored by

reading in the contents of Command Register 0. The

bit-format of Command Register 0 is presented be-

low.

If the ALOS bit-field contains a “1”, the XRT73LC00 is

currently declaring an ALOS condition. If the ALOS

bit-field contains a “0”, the device is NOT currently de-

claring an ALOS condition.

Disabling the ALOS Detector

It is useful to disable the ALOS Detector in the

XRT73LC00 for debugging purposes. If the

XRT73LC00 is operating in the HOST Mode, the

ALOS Detector can be disabled by writing a “1” into

the ALOSDIS bit-field in Command Register 2 as de-

picted below.

NOTE: Setting both the ALOSDIS and DLOSDIS bit-fields

to “1” disables LOS Declaration in the XRT73LC00.

2. The Digital LOS (DLOS) Declaration/Clear-

ance Criteria

The XRT73LC00 declare a Digital LOS (DLOS) con-

dition if the XRT73LC00 detects 160±32 or more con-

secutive “0’s” in the incoming data.

The XRT73LC00 clears DLOS if it detects four con-

secutive sets of 32 bit-periods each of which contains

at least 10 “1’s” (e.g., average pulse density of greater

than 33%).

Monitoring the State of DLOS

If the XRT73LC00 is operating in the HOST Mode,

the state of DLOS can be polled or monitored by

reading in the contents of Command Register 0 as

shown.

If the DLOS bit-field contains a “1”, the XRT73LC00 is

currently declaring a DLOS condition. If the DLOS

bit-field contains a “0”, the device is NOT currently de-

claring the DLOS condition.

Disabling the DLOS Detector

It is useful to disable the DLOS Detector in the

XRT73LC00 for debugging purposes. If the

XRT73LC00 is operating in the HOST Mode, the

DLOS Detector can be disabled by writing a “1” into

the DLOSDIS bit-field in Command Register 2.

NOTE: Setting both the ALOSDIS and DLOSDIS bit-fields

to a “1” disables LOS Declaration in the XRT73LC00.

3.6.3

Muting the Recovered Data while the LOS

is being Declared

In some applications it is not desirable for the

XRT73LC00 E3/DS3/STS-1 LIU to recover data and

route it to the Receiving Terminal while the LIU is de-

claring a LOS condition. The LOS Muting feature, if

enabled, causes the XRT73LC00 to halt transmission

of the recovered data to the Receiving Terminal while

the LOS condition is True. In this case, the RPOS

and RNEG output pins are forced to “0”. Once the

LOS condition has been cleared, the XRT73LC00 re-

sumes the transmission of the recovered data to the

Receiving Terminal. The XRT73LC00 allows en-

abling of the Muting Upon LOS feature by either of

the following means.

If the XRT73LC00 is Operating in the Hardware

Mode:

The Muting Upon LOS feature is enabled by pulling

the LOSMUTEN input pin (pin 19) to VDD.

If the XRT73LC00 is Operating in the HOST Mode:

COMMAND REGISTER CR0 (ADDRESS = 0X00)

RLOL

RLOS

ALOS

DLOS

DMO

Read

Only

Read

Only

Read

Only

Read

Only

Read

Only

COMMAND REGISTER CR2 (ADDRESS = 0X02)

Reserved ENDECDIS ALOSDIS DLOSDIS REQDIS

COMMAND REGISTER CR0 (ADDRESS = 0X00)

RLOL

RLOS

ALOS

DLOS

DMO

Read

Only

Read

Only

Read

Only

Read

Only

Read

Only

COMMAND REGISTER CR2 (ADDRESS = 0X02)

Reserved ENDECDIS ALOSDIS DLOSDIS REQDIS

XRT73LC00 Datasheet(PDF) 38 Page - Exar Corporation

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