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PRELIMINARY
XRT79L71
68
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
bit-fields are not processed by the Receive DS3/E3 Framer block, within the XRT79L71, and the Transmit
DS3/E3 Framer block will automatically set these particular bit-fields to "1" within each outbound DS3 frame.
However, to support such a proprietary data link, use the Transmit Overhead Data Input Interface block and the
Receive Overhead Data Output Interface block in order to support the transmission/reception of data via these
and the Receive Overhead Data Output Interface block in detail, respectively.
DL - Path Maintenance Data Link Bits (C-bit Parity Framing Format only)
The purpose of these bit-fields is to support the transmission/reception of the Path Maintenance Data Link
between any two pieces of DS3 Terminal Equipment. The transmission/reception of the PMDL data will be
handled by the Transmit LAPD Controller and the Receive LAPD Controller blocks, respectively.
For information on how the Transmit LAPD Controller and the Receive LAPD Controller handle LAPD/PMDL
4.2
THE TRANSMIT DIRECTION - DS3 CLEAR-CHANNEL FRAMER APPLICATIONS
Now that the basics of the DS3 frame structure have been discussed, the next several sections present an in-
depth functional description of all of the blocks that are operating in the Transmit Direction, within the
XRT79L71, when configured to operate in the Clear-Channel DS3 Framer Mode. Figure 28 presents a
functional block diagram of the Transmit Direction circuitry within the XRT79L71.
Figure 28 indicates that the Transmit Direction circuitry consists of the following functional blocks.
The Transmit Payload Data Input Interface block
FIGURE 28. ILLUSTRATION OF THE FUNCTIONAL BLOCK DIAGRAM OF THE TRANSMIT DIRECTION CIRCUITRY WHEN
THE
XRT79L71 HAS BEEN CONFIGURED TO OPERATE IN THE DS3 CLEAR-CHANNEL FRAMER MODE
Transmit
Payload Data
Input
Interface
Block
Transmit
Payload Data
Input
Interface
Block
Transmit
DS3/E3
Framer
Block
Transmit
DS3/E3
Framer
Block
Tranmit
DS3/E3
LIU Block
Tranmit
DS3/E3
LIU Block
TxSer
TxNib[3:0]
TxInClk
TRING
TTIP
Transmit
Overhead Data
Input Interface
Block
Transmit
Overhead Data
Input Interface
Block
TxOHClk
TxOHIns
TxOHInd
TxOH
TxOHEnable
TxOHFrame
TxNibClk
TxFrame
Tx LAPD
Controller
Block
Tx LAPD
Controller
Block
From Microprocessor
Interface Block
Tx LAPD
Buffer
(90 Bytes)
Tx LAPD
Buffer
(90 Bytes)
Tx FEAC
Processor
Block
Tx FEAC
Processor
Block