
XRT72L56
SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.2
193
The XRT72L56 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 XRT72L56 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 XRT72L56 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.
F
IGURE
65. A
PPROACH
TO
I
NTERFACING
THE
XRT72L56 F
RAMER
IC
TO
THE
XRT73L03 DS3/E3/STS-1 T
RANS
-
MITTER
LIU (
ONE
CHANNEL
SHOWN
)
RxAVDD_0
RD*
WR*
R4
31.6
R7
4.7k
R2
37.4
RxSERIAL_CLK_0
TxAVDD_0
HW_RESET*
0.01uF
T1
T3001
1
6
3
4
0.01uF
44.736MHz
READY_OUT*
ALE
R3
31.6
A[11:0]
XRT71D03_CS* (Optional)
U2
XRT73L03IV_Ch_0
28
26
29
27
72
71
30
31
51
50
49
33
32
34
47
70
48
73
54
55
57
117
67
42
37
39
61
62
63
64
96
TxAVDD0
TxAGND0
TTIP0
TRING0
RTIP0
RRING0
MTIP0
MRING0
RPOS0
RNEG0
RCLK0
TPDATA_0
TNDATA_0
TCLK_0
RxAVDD0
RxDVDD0
RxAGND0
RxDGND0
RLOS_0
TxOFF_0
LOSTHR_0
TxAVDD0
TxAGND0
CS
SDI
SDO
DVDD_0
Rx_LOS_Ch_0
T2
T3001
1
6
3
4
R1
37.4
0.01uF
XRT72L56_INT*
D[7:0]
J1
BNC
1
2
C2
0.01uF
J2
BNC
1
2
RxFRAME_0
TxFRAME_0
0.01uF
R5
270
R6
270
U3
XRT72L56_Ch_0
J1
K4
J2
D8
D6
J3
B6
C8
B7
D10
C7
C6
H2
G1
J4
T25
T24
M24
M25
M26
N23
N24
N25
N26
P26
P23
L26
L25
L24
L23
K25
K24
J26
K23
J25
R24
R23
T23
J24
U26
C15
H3
B12
C9
B9
A9
A8
B8
A7
D9
R25
P24
P25
R26
TxPOS_0
TxNEG_0
TxLineClk_0
TxDMO_0
ERLOL_0
LREQB_0
RLOOP_0
TAOS_0
ENCODIS_0 (TxOFF_0)
RxPOS_0
RxNEG_0
RxLineClk_0
RESET
A0
A1
A2
A3
A4
A5
A6
A7
A8
D0
D1
D2
D3
D4
D5
D6
D7
CS
INT
WR_RW
TxSer_0
MOTO
RxLOS_0
NIBBLEINTF
A9
A10
A11