XRT7250 datasheet(393/463 Pages) EXAR

393 / 463 page

XRT7250

áç

DS3/E3 FRAMER IC

REV. 1.1.1

374

For E3 applications, the Transmit E3 Framer block au-

tomatically generates and inserts the framing align-

ment bytes (e.g., the "FA1” and “FA2” framing align-

ment bytes) into the Outbound E3 frames. Further,

the Transmit E3 Framer block will automatically com-

pute and insert the EM byte into the Outbound E3

frames. Hence, the Transmit E3 Framer block will not

accept data from the Transmit OH Data Input Inter-

face block for the "FA1”, “FA2” and “EM” bytes.

However, the Transmit E3 Framer block will accept

(and insert) data from the Transmit Overhead Data In-

put Interface for the following byte-fields.

• MA byte

• TR byte

• NR byte

• GC byte

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 or bytes,

then the Transmit E3 Framer block will insert this data

into the appropriate overhead bit/byte-fields, within

the Outbound E3 frames.

6.2.4.2

Detailed Functional Description of the

Transmit E3 Framer Block

The Transmit E3 Framer receives data from the fol-

lowing three sources and combines them together to

form a E3 data stream.

• The Transmit Payload Data Input Interface block.

• The Transmit Overhead Data Input Interface block

• The Transmit HDLC Controller block.

Afterwards, this E3 data stream will be routed to the

Transmit E3 LIU Interface block, for further process-

ing.

Figure 177 presents a simple illustration of the Trans-

mit E3 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 E3 frames, the Transmit E3 Framer

block has the following roles.

• Generating Alarm Conditions

• Generating Errored Frames (for testing purposes)

• Routing Outbound E3 frames to the Transmit E3

LIU Interface block

Each of these additional roles are discussed below.

6.2.4.2.1

Generating Alarm Conditions

The Transmit E3 Framer block permits the user to, by

writing the appropriate data into the on-chip registers,

to override the data that is being written into the

Transmit Payload Data and Overhead Data Input In-

terfaces and transmit the following alarm conditions.

• Generate the Yellow Alarms (or FERF indicators)

• Manipulate the FERF-bit, within the MA byte (set

them to "0")

• Generate the AIS Pattern

• Generate the LOS pattern

• Generate FERF (Yellow) Alarms, in response to

detection of a Red Alarm condition (via the Receive

Section of the XRT7250).

FIGURE 177. A SIMPLE ILLUSTRATION OF THE TRANSMIT E3 FRAMER BLOCK AND THE ASSOCIATED PATHS TO

OTHER

FUNCTIONAL BLOCKS

Transmit

E3 Framer

Block

Transmit

E3 Framer

Block

Transmit HDLC

Controller/Buffer

Transmit Overhead

Data Input Interface

Transmit Payload Data

Input Interface

To Transmit E3 LIU Interface Block

XRT7250 Datasheet(PDF) 393 Page - Exar Corporation

XRT7250 Datasheet(HTML) 393 Page - Exar Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL