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PEB 20550
PEF 20550
Overview
Semiconductor Group
28
01.96
The control channel is unidirectional and forwards the status information of the
corresponding D-channel (blocked or available) towards the subscriber terminal.
Different existing channel structures are used to implement the control channel between
the HDLC-controllers on the line card and in the subscriber terminal.
Control Channel Implementation on the U
PN
-Interface
On an U
PN
-line card, the control channel is either integrated in the C/I-channel or uses
the MR-bit, depending on the connected layer-1 device (OCTAT-P -> C/I channel, IBC
-> MR-bit).
The U
PN
-transceiver uses the T-channel to transmit the control channel information to the
terminal. The T-channel is a sub channel of the U
PN
-interface with a bandwidth of 2 kbit/
s.
In the subscriber terminal the control channel is included again in the IOM-2 protocol.
Depending on the terminal configuration two alternatives can be selected in the terminal
transceiver device.
The blocked/available information is translated directly into the S/G-bit (Stop/Go) when
no subsequent transceiver circuit is present in the terminal. The S/G-bit is evaluated by
the terminal HDLC-controller ICC. It stops data transmission immediately when the S/
G-bit is set to 1.
Figure 8
Control Channel Implementation with IBC (PEB 2095) as Line Card Transceiver
ITS05809
HDLC Controller
U
Trans-
ceiver
ICC
(optional)
DSAC-P
S/G
S/G = 1
S/G = 0
Blocked
Available
MR = 1
MR = 0
IBC
ELIC
MR
T
T = 1
T = 0
R
Available
Blocked
Available
Blocked
p0