XRT72L13 datasheet(207/370 Pages) EXAR

207 / 370 page

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XRT72L13

M13 MULTIPLEXER/CLEAR CHANNEL DS3 FRAMER IC

PRELIMINARY

REV. P1.0.6

195

Bit 5 - RxDS1Clk Gapped (CRC-32) Select

The exact functionality of this bit-field depends upon

whether the user is operating the XRT72L13 in the

“M13-Channelized” or in the “High Speed HDLC Con-

troller” Mode.

M13-Channelized Mode - RxDS1 Gapped Clock

Select

In the “M13-Channelized” Mode, then this bit-field

permits the user to either enable or disable the 28

Digital PLL blocks within the XRT72L13 M13 device.

Setting this bit-field to “0” enables all 28 of these Dig-

ital PLL blocks. In this mode, all 28 (or 21) of the

RxDS1Clk and RxDS1Data output signals will be

smoothed by an internal Digital PLL. This permits the

user to interface the “Receive DS1/E1” Output inter-

face to an external DS1 or E1 LIU IC.

Setting this bit-field to “1” disables all 28 of these Dig-

ital PLL blocks. In this mode, all 28 (or 21) of the

RxDS1Clk and RxDS1Data output signals will NOT

be smoothed by an internal Digital PLL, and will con-

tain gaps.

HDLC Controller Mode - CRC16/32 Select

In the “High Speed HDLC Controller” Mode, this bit-

field permits the user to configure the XRT72L13 to

compute and verify a CRC-16 or CRC-32 value within

the HDLC frame.

Setting this bit-field to “0” configures the XRT72L13 to

compute and verify a CRC-16 value in each HDLC

frame.

Setting this bit-field to “1” configures the XRT72L13 to

compute and verify a CRC-32 value in each HDLC

frame.

Bit 4 - M13 Disable

This bit-field along with “Payload HDLC Controller En-

able” (bit 6) pemits the user to specify whether the

XRT72L13 M13 device is to operate in either of the

following modes.

• The “M13/Channelized” Mode

• The “DS3 Clear Channel Framer” Mode

• The “High Speed HDLC Controller” Mode.

The relationship between these two bit-fields and the

resulting operating operating mode of the XRT72L13

M13 device is tabulated below.

Bit 3 - M13Loopback/Remote Loopback

The exact functionality of this bit-field depends upon

whether the user is operating the XRT72L13 in the

“M13-Channelized” or in the “High Speed HDLC Con-

troller” Mode.

M13-Channelized Mode - M13 Loopback Select

If the XRT72L13 is operating in the “M13 Channel-

ized” Mode, then this bit-field functions as the “M13

Loopback” select bit-field.

Setting this bit-field to “0” disables the “M13 Loop-

back” Mode. In this mode, the Receive M13 Block will

accept data from the Rx DS3 Framer block (Normal

Operation).

PAYLOAD HDLC

CONTROLLER

ENABLE

M13 DISABLE

RESULTING

OPERATING MODE

M13/

Channelized

Mode

DS3 Clear

Channel Framer

Mode

M13/

Channelized

Mode

High Speed

HDLC Controller

Mode

PAYLOAD HDLC

CONTROLLER

ENABLE

M13 DISABLE

RESULTING

OPERATING MODE

M13/

Channelized

Mode

DS3 Clear

Channel Framer

Mode

M13/

Channelized

Mode

High Speed

HDLC Controller

Mode

XRT72L13 Datasheet(PDF) 207 Page - Exar Corporation

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