XRT72L50 Datasheet, PDF (463/471 Pages) Exar Corporation – SINGLE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

áç
XRT72L50
SINGLE CHANNEL DS3/E3 FRAMER WITH HDLC CONTROLLER
REV. 1.2.1
7.0 DIAGNOSTIC OPERATION OF THE XRT72L50 FRAMER IC
The XRT72L50 DS3/E3 Framer IC permits the user to command it to operate in the Framer Local Loop-back
Mode. When the user does this then the data will be as follows.
1. Data enters the XRT72L50 via both the Transmit Payload Data Input Interface and the Transmit Overhead
Data Input Interface blocks.
2. This data is processed through the Transmit DS3/E3 Framer block and the Transmit DS3/E3 LIU Interface
block.
3. This Transmit Output data is internally looped-back into the Receive Path via the Receive LIU Interface
block.
4. This data will be processed through the Receive DS3/E3 Framer block and arrive at both the Receive Pay-
load Data Output Interface and Receive Overhead Data Output Interface blocks, where this data outputs to
the terminal equipment.
The Framer Local Loop-back Path is illustrated in Figure 200.
FIGURE 200. THE FRAMER LOCAL LOOP-BACK PATH WITHIN THE XRT72L50 DS3/E3 FRAMER IC
TxO H Fram e
TxOHEnable
TxOH
T xO H C lk
T xO H In s
T xO H In d
TxSer
T xN ib [3 :0]
TxInClk
T xN ib C lk
TxF ram e
TxNibFram e
TxF ram eR ef
A [8 :0 ]
W R_R/W
RD_DS
CS
ALE_AS
Reset
Int
D[7:0]
MOTO
RDY_DTCK
RxOHInd
RxSer
RxNib[3:0]
RxClk
R xF ram e
R xO H F ram e
RxOHEnable
RxOH
R xO H C lk
Transmit
Overhead Input
Interface Block
Transmit
Payload Data
Input
Interface Block
M ic ro proc e s s o r
&
Program mable
Registers
Receive
Payload Data
O u tp u t
Interface Block
Receive
Overhead Input
Interface Block
Transmit DS3/E3
Fram er Block
Transmit LAPD
B uffe r/C o ntroller
Receive LAPD
B uffe r/C o ntroller
Receive DS3/E3
Fram er Block
Transmit LIU
Interface Block
Receive LIU
Interface Block
TxPOS
TxNEG
T x L in eC lk
Framer
Local
Loop-back
Path
RxPOS
RxNEG
RxLineClk
The user can configure the XRT72L50 into the Framer Local-Loop-back Mode by writing a “1” into bit-field 7
(Local Loop-back) within the Framer Operating Mode Register, as illustrated below.
450