XRT7250 datasheet(187/463 Pages) EXAR

187 / 463 page

XRT7250

DS3/E3 FRAMER IC

áç

REV. 1.1.1

168

If the user's local Data Link Equipment activates the

Transmit Overhead Data Input Interface block and

writes data into this interface for these bits, then the

Transmit DS3 Framer block will insert this data into

the appropriate overhead bit-fields, within the out-

bound DS3 frames.

Handling of Data from the Transmit HDLC Con-

troller block

The exact manner in how the Transmit DS3 Framer

handles data from the Transmit HDLC Controller

block depends upon whether the Transmit HDLC

Controller is transmitting BOS (Bit Oriented Signal-

ing) or MOS (Message Oriented Signaling) data.

If the Transmit DS3 HDLC Controller block is not acti-

vated, then the Transmit DS3 Framer block will insert

a “1” into each FEAC and “DL” bit-field, within each

outbound DS3 frame.

If the Transmit DS3 HDLC Controller block is activat-

ed, and is configured to transmit either a “BOS” or

“MOS” type message, then data will be inserted into

the FEAC and “DL” bit-fields as described in Section

3.2.3.

4.2.4.2

Detailed Functional Description of the

Transmit DS3 Framer Block

The Transmit DS3 Framer receives data from the fol-

lowing three sources and combines them together to

form a DS3 data stream.

• The Transmit Payload Data Input Interface block.

• The Transmit Overhead Data Input Interface block

• The Transmit HDLC Controller block.

Afterwards, this DS3 data stream will be routed to the

Transmit DS3 LIU Interface block, for further process-

ing.

Figure 64 presents a simple illustration of the Trans-

mit DS3 Framer block, along with the associated

paths to the other functional blocks within the chip.

In addition to taking data from multiple sources and

multiplexing them, in appropriate manner, to create

the outbound DS3 frames, the Transmit DS3 Framer

block has the following roles.

• Generating Alarm Conditions

• Generating Errored Frames (for testing purposes)

• Routing outbound DS3 frames to the Transmit DS3

LIU Interface block

Each of these additional roles are discussed below.

FIGURE 64. A SIMPLE ILLUSTRATION OF THE TRANSMIT DS3 FRAMER BLOCK AND THE ASSOCIATED PATHS TO

OTHER

FUNCTIONAL BLOCKS

Transmit

DS3 Framer

Block

Transmit

DS3 Framer

Block

Transmit HDLC

Controller/Buffer

Transmit Overhead

Data Input Interface

Transmit Payload Data

Input Interface

To Transmit DS3 LIU Interface Block

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