XRT72L13 datasheet(68/370 Pages) EXAR

68 / 370 page

XRT72L13

MULTIPLEXER/FRAMER IC

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PRELIMINARY

REV. 1.0.6

• Set the “X” bits (within each “outbound” DS2 frame)

to the appropriate value in order to reflect the “DS2

FERF” indicator when conditions warrant.

The XRT72L13 will accept up to 28 DS1 lines or up to

21 E1 lines as inputs to the M12 Multiplexer. Associ-

ated with each of these DS1 or E1 lines is an input

clock signal that the device will use to sample and

latch into the device.

In all, the M12 MUX is capable of MUXing 28 DS1

lines into 7 DS2 lines. Additionally, the M12 MUX is

also capable of MUXing 21 E1 lines into 7 ITU-T

G.747 lines.

1.1.1.2

Operation of the M23 MUX

The M23 MUX, within the XRT72L13 will accept up to

7 DS2 or ITU-T G.747 data streams and will MUX

these signals into a DS3 data stream. Afterwards,

this DS3 data stream will be routed to the "Clear

Channel DS3 Framer" block for further processing.

1.1.1.3

Operation of the "Clear Channel DS3

Framer Block"

Once this data is routed to the "Clear Channel DS3

Framer Block", the DS3 data stream will be encapsu-

lated into a "outbound" DS3 framing structure, and

will be transmitted to an off-chip LIU IC. The Clear

Channel DS3 Framer Block is also responsible for a

variety of other necessary function, such as:

• Transmission of PMDL (Path Maintenance Data

Link) Messages

• Transmission of FEAC (Far-End Alarm & Control)

Messages

• Transmission of the FERF (Far-End Receive Fail-

ure) Indicator

• Transmission of the FEBE (Far-End Block Error)

Indicator

• Computation of P and CP-Bits

1.1.2

In the Receive Direction

When the XRT72L13 is operating in the "Multiplexer/

De-Multiplexer" Mode, the data (in the "Receive Di-

rection") passes through the following block.

• The Clear Channel DS3 Framer Block

• An M23 DEMUX

• An M12 DEMUX

1.1.2.1

Operation of the Clear Channel DS3

Framer Block

The purpose of the "Clear Channel DS3 Framer

Block" is to perform the following functions:

• To verify the P and CP-bits.

• To Terminate the PMDL Messages.

• To Terminate the FEAC Messages

• To Terminate and interpret the FERF Indicator

• To Terminate and interpret the FEBE Indicator.

• To strip off the "Overhead" bytes and route the pay-

load portion of the "inbound" DS3 frame to the M23

DEMUX

1.1.2.2

Operation of the M23 DEMUX

The purpose of the M23 DEMUX, within the

XRT72L13 is to accept this DS3 data stream and de-

multiplex either 7 DS2 or ITU-T G.747 data streams.

Afterwards, these data streams will be routed to the

M12 DEMUX.

1.1.2.3

Operation of the M12 DEMUX

The purpose of the M12 DEMUX, within the

XRT72L13 is to accept either the 7 DS2 or ITU-T

G.747 data streams and to de-multiplex up to 28 DS1

signals or up to 21 E1 signals.

1.1.3

Diagnostic Resources available for MUX/

DEMUX Mode

In all, the XRT72L13 supports two types of loop-back

modes, while it is configured to operate in the "MUX/

DEMUX" Mode.

• DS1/E1 Tributary Loop-Back

• DS2/ITU-T G.747 Tributary Loop-Back

Each of these Loop-Back Modes are briefly dis-

cussed below.

1.1.3.1

DS1/E1 Tributary Loop-Back

Figure 27 presents an illustration of the XRT72L13

operating in the "DS1/E1 Tributary Loop-Back Mode.

XRT72L13 Datasheet(PDF) 68 Page - Exar Corporation

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