PEB2085 SIEMENS [Siemens Semiconductor Group], PEB2085 Datasheet - Page 81

• Manufacturer Part Number: PEB2085
• Description: ISDN SubscribernAccess Controller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

2.5.1
According to CCITT recommendation I.430 pseudo-ternary encoding with 100% pulse width is
used on the S/T interface. A logical "1" corresponds to a neutral level (no current), whereas
logical "0" ’s are encoded as alternating positive and negative pulses. An example is shown in
figure 42.
Figure 42
S/T Interface Line Code
One frame consists of 48 bits, at a nominal bit rate of 192 kbit/s. Thus each frame carries two
octets of B1, two octets of B2, and four D-bits, according to the B1+B2+D structure defined for
the ISDN basic access (total useful data rate: 144 kbit/s). Frame begin is marked using a code
violation (no Mark inversion). The frame structures (from network to subscriber, and subscriber
to network) are shown in figure 43.
Figure 43
Frame Structure at Reference Points S and T (CCITT I.430)
Note: Dots demarcate those parts of the frame that are independently DC-balanced.
Semiconductor Group
NT
TE
TE
NT
S/T Interface
1
0
0
F = Framing Bit
L
D
E
F
DL.
A
0
1
0
=
=
=
=
DC Balancing Bit
D-Channel Bit
D-Echo-Channel Bit
Auxiliary Framing Bit or Q-Bit
F
D
2 Bits Offset
L.
L.
F L.
t
B1
+
0 V
V -
V
B1
E D A F N
L.
D
A
L.
0
F
A
L.
1
B2
0
B2
48 Bits in 250 µs
0
81
N
B1 = Bit within B Channel
B2 =
A = Bit used for Activation
S = Subchannel SC1 through SC5 bit position
M = Multiframing Bit
=
1
Bit set to a Binary Value N
E D M
Bit within B Channel
1
L.
D
L.
0
0
B1
B1
0
1
2
1
ITD00322
Functional Description
E
=
D
F
A
1
S
L. D L.
B2
B2
E D L. F L.
L.
D
ITD02330
L.
F
L.