XRT72L58 Datasheet, PDF (207/486 Pages) Exar Corporation – EIGHT CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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EIGHT CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
XRT72L58
REV. P1.1.2
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.
FIGURE 64. A SIMPLE ILLUSTRATION OF THE TRANSMIT DS3 FRAMER BLOCK AND THE ASSOCIATED PATHS TO
OTHER FUNCTIONAL BLOCKS
Transmit HDLC
Controller/Buffer
Transmit Overhead
Data Input Interface
Transmit Payload Data
Input Interface
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To Transmit DS3 LIU Interface Block
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.
4.2.4.2.1 Generating Alarm Conditions
The Transmit DS3 Framer block permits the user to,
by writing the appropriate data into the on-chip regis-
ters, 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 X-bit (set them to 1)
• Generate the AIS Pattern
• Generate the IDLE pattern
• Generate the LOS pattern
• Generate FERF (Yellow) Alarms, in response to
detection of a Red Alarm condition (via the Receive
Section of the XRT72L58).
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