
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
á
PRELIMINARY
REV. P1.1.7
193
The XRT72L53 Framer IC is a digital device that
takes DS3 payload and overhead bit information from
some terminal equipment, processes this data and ul-
timately, multiplexes this information into a series of
outbound DS3 frames. However, for DS3 coaxial ca-
ble applications, the XRT72L53 Framer IC lacks the
current drive capability to be able to directly transmit
this DS3 data stream through some transformer-cou-
pled coax cable with enough signal strength for it to
comply with the Isolated Pulse Template require-
ments and be received by the remote receiver.
Therefore, in order to get around this problem, the
Framer IC requires the use of an LIU (Line Interface
Unit) IC. An LIU is a device that has sufficient drive
capability, along with the necessary pulse-shaping
circuitry to be able to transmit a signal through the
transmission medium in a manner that it can (1) com-
ply with the DSX-3 Isolated Pulse Template require-
ments and (2) be reliably received by the Remote Ter-
minal Equipment.
Figure 65 presents a circuit draw-
ing depicting the Framer IC interfacing to an LIU
(XRT7300 DS3/E3/STS-1 Transmit LIU).
The Transmit Section of the XRT72L53 contains a
block which is known as the Transmit DS3 LIU Inter-
face block. The purpose of the Transmit DS3 LIU In-
terface block is to take the outbound DS3 data
stream, from the Transmit DS3 Framer block, and to
do the following:
1. Encode this data into one of the following line
codes
a. Unipolar (e.g., Single-Rail)
b. AMI (Alternate Mark Inversion)
c. B3ZS (Bipolar 3 Zero Substitution)
2. And to transmit this data to the LIU IC.
Figure 66 presents a simple illustration of the Trans-
mit DS3 LIU Interface block.
FIGURE 65. APPROACH TO INTERFACING THE XRT72L53 FRAMER IC TO THE XRT73L03 DS3/E3/STS-1 TRANS-
MITTER
LIU (ONE CHANNEL SHOWN)
5V
U1
XRT72L5x
TxPOS
TxNEG
TxLineClk
DMO
ExtLOS
RLOL
LLOOP
RLOOP
TAOS
TxLEV
ENCODIS
REQB
RxPOS
RxNEG
RxLineClk
MOTO
27
RESETB
28
A0
15
A1
16
A2
17
A3
18
A4
19
A5
20
A6
21
A7
22
A8
23
D0
32
D1
33
D2
34
D3
35
D4
36
D5
37
D6
38
D7
39
Rdy_Dtck
6
WRB_RW
7
RDB_DS
10
CSB
8
ALE_AS
9
INTB
13
TxSER
46
TxInClk
43
TxFrame
61
RxSer
86
RxClk
88
RxFrame
90
RxLOS
95
RxOOF
94
RxRED
93
RxAIS
87
NIBBLEINTF
25
U2
XRT73L0x
TPDATA
TNDATA
TCLK
RCLK1
31
RNEG
32
RPOS
33
TTIP
41
TRING
40
MTIP
44
MRING
43
RRING
9
RTIP
8
DMO
RLOS
RLOL
LLB
RLB
TAOS
TxLEV
ENCODIS
REQDIS
T1
1:1
1
5
4
8
T2
1:1
1
5
4
8
R1
36
1
2
R2
36
1
2
R6
37.5
1
2
R3
270
1
2
R4
270
1
2
R5
37.5
1
2
C1
0.01uF
1
2
TxSER
TxInClk
NIBBLEINTF
RESETB
RTIP
RRING
CSB
RW
DS
AS
TxFrame
RxSer
RxClk
RxFrame
RxLOS
RxOOF
RxRED
RxAIS
A[8:0]
TRING
TTIP
INTB
D[7:0]
INTB