User`s manual
Am186
TM
CC Microcontroller ISDN TA Reference Design Manual
2-9
ISDN U Interface
The Lucent T7237 circuit is used to provide the two-wire 2B+D U interface. This
device has a PCM serial microprocessor interface and an SSI (synchronous serial
interface). These interfaces are used to transfer data to and from the Am186CC
microcontroller using it’s integrated HDLC. This chip provides the two-wire
network termination. It processes the ISDN BRI bit stream that consists of two 64-
kbps B channels and a single 16-kbps D channel. The schematic for the U interface
block is shown in Figure 2-6. The U-interface circuit includes a line fuse, U
transformer, DC termination IC, and opto-isolation circuitry. The LED shown in
Figure 2-6 is used to indicate device status. The four states of the LED are Low,
High, 1 Hz, and 8 Hz. Refer to the Lucent T7237 device data sheet for a complete
description.
The U-interface data is in 2B1Q format, which provides a four-level (quaternary)
amplitude modulation. A single quaternary symbol represents two binary bits. The
quaternary symbols are ± 3, ± 1, which represent 00, 01, 10, and 11 in binary.
Figure 2-6. ISDN TA U Interface Circuit
TIP
RING
VCC5
VCC5
VCC5
VCCAU
VCCAU
VCCAU
VCC5
VCC5
VCC5
VCCAU
X2
15.36011MHz
1 2
CR1
LED SOT-23
Lumex SSL-LX15IGC-RP-TR
3
2
1
CATH
GREEN
ORANGE
U8
LH1465AB
1
2
3
45
6
7
8
PR+
T
R
PR-COM
PD
RS
TC
U11
SM6T6V8CA
12
U12
P2300SB
12
U7
6N139
2
3
8
7
6
5
1
4
Anode
Cathode
Vcc
VB
VO
GND
NC
NC
U9
T7237A PLCC
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
1
2
3
4
5
6
TDMDI
TDMD0
TDMCLK
GNDD
INT#
SDI
VDDD
SDO
SCK
GNDD
CKOUT
GNDO
VDDO
X1
X2
VDDA
NC
NC
GNDA
NC
NC
VRCM
VRP
VRN
HN
LOP
VDDA
GNDA
LON
HP
SDINN
SDINP
VDDA
GNDA
GNDA
VDDA
RESET#
HIGHZ#
GNDD
OPTOIN
STLED
FS
VDDD
ILOSS#
C29
3300pF
C31
3300pF
C30 1.0uF
C28 820pF
5%
C27 1.0uF
C32
0.1uF
C33
0.1uF
C34
0.1uF
R13
17.8K
0805
1%
R15 1.1K
R20 2.2M
0805
R19 1.1K
R21 21
1206
+/- 1%, 1/4W
R22
16.9
1206
1%
R23
16.9
1206
1%
R16
137
0805
1%
R18
137
0805
1%
R14
10K
0805
R24 10K
R17 270
P1
RJ45A
1
2
3
4
5
6
7
8
11
12
1
2
3
4
5
6
7
8
GND1
GND2
F1
FUSE
U10
Pulse T4008
U Transformer
1
5
9
6
10
7
SCLK
RESOUT#
FSCA
TXDA
SD ATA
RXDA
CLKA
INT2
about.book Page 9 Friday, December 18, 1998 9:41 AM