PRELIMINARY
XRT79L71
354
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
5.3
THE RECEIVE DIRECTION
The next several sections will present an in-depth functional description of all of the blocks that are operating in
the Receive Direction, within the XRT79L71, when configured to operate in the "Clear-Channel E3 Framer"
Mode. Figure 163 presents a functional block diagram of the Receive Direction circuitry within the XRT79L71.
Figure 163 indicates that the Receive Direction circuitry consists of the following functional blocks.
The Receive E3 LIU block
The Receive E3 Framer Block
The Receive LAPD Controller Block
The Receive Payload Data Output Interface Block
The Receive Overhead Data Output Interface Block
5.3.1
THE RECEIVE E3 LIU BLOCK
The Receive E3 LIU Block is the first functiona block (within the Receive Direction) of the XRT79L71 that we
will discuss for Clear-Channel Framer Applications.
Figure 164 presents an illustration of the "Receive
Direction" circuitry whenever the XRT79L71 has been configured to operate in the E3, ITU-T G.751 Clear-
Channel Framer Mode, with the Receive E3 LIU Block highlighted.
FIGURE 163. ILLUSTRATION OF THE FUNCTIONAL BLOCK DIAGRAM OF THE RECEIVE DIRECTION CIRCUITRY WHEN-
EVER THE
XRT79L71 HAS BEEN CONFIGURED TO OPERATE IN THE E3 CLEAR-CHANNEL FRAMER MODE
Receive
Payload Data
Input
Interface
Block
Receive
Payload Data
Input
Interface
Block
Receive
DS3/E3
Framer
Block
Receive
DS3/E3
Framer
Block
Receive
DS3/E3
LIU Block
Receive
DS3/E3
LIU Block
RxSer
RxNib[3:0]
RxClk
RRING
RTIP
Receive
Overhead Data
Input Interface
Block
Receive
Overhead Data
Input Interface
Block
RxOHClk
RxOHInd
RxOH
RxOHEnable
RxOHFrame
RxNibClk
RxFrame
Rx LAPD
Controller
Block
Rx LAPD
Controller
Block
From Microprocessor
Interface Block
Rx LAPD
Buffer
(90 Bytes)
Rx LAPD
Buffer
(90 Bytes)