XRT72L56
SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.2
á
PRELIMINARY
293
As the Transmit E3 Framer block formulates the out-
bound E3 frames, the contents of the BIP-4 bits are
automatically XORed with the contents of this regis-
ter. The results of this XOR operation is written back
into the corresponding bit-field within the outbound
E3 frame, and is transmitted to the Remote Terminal
Equipment. Therefore, if the user does not wish to
modify any of these bits, then this register must con-
tain all “0’s” (the default value).
N
OTE
:
This register is only active if the XRT72L56 Framer
IC has been configured to insert the BIP-4 nibble into each
outbound E3 frame.
5.2.5
The XRT72L56 Framer IC is a digital device that
takes E3 payload and overhead bit information from
some terminal equipment, processes this data and ul-
timately, multiplexes this information into a series of
outbound E3 frames. However, the XRT72L56 Fram-
er IC lacks the current drive capability to be able to di-
rectly transmit this E3 data stream through some
transformer-coupled coax cable with enough signal
strength for it to be received by the remote receiver.
The Transmit E3 Line Interface Block
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 be reli-
ably received by the far-end receiver. Figure 120 pre-
sents a circuit drawing depicting the Framer IC inter-
facing to an LIU (XRT7300 DS3/E3/STS-1 Transmit
LIU).
TXE3 BIP-4 ERROR MASK REGISTER (ADDRESS = 0X4A)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Not Used
TxBIP-4 Mask[3:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
F
IGURE
120. A
PPROACH
TO
I
NTERFACING
THE
XRT72L56 F
RAMER
IC
TO
THE
XRT73L03 DS3/E3/STS-1 LIU
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