MTC-20172-PC AMI Semiconductor, Inc., MTC-20172-PC Datasheet - Page 25

• Manufacturer Part Number: MTC-20172-PC
• Description: S Interface Circuit for ISDN (SIC)
• Manufacturer: AMI Semiconductor, Inc.

This is needed in LT-T and TE
applications, when multiple S-devices
are sourcing on the same S-bus (short
passive or extended bus).
In TE/LT-T, the S-bus transceiver
provides the D-channel access
protocol, in collaboration with an
intelligent HDLC transmitter at the GCI
bus side.
For details, please refer to chapter 5.
4.6 The GCI
At the digital control interface, the
MTC-20172 SIC is connected via a
bidirectional serial interface - a digital
bus called the General Circuit
Interface (GCI), which is similar to the
ISDN Oriented Modular (IOM™)
interface.
This bus is logically organized as
many parallel point-to-point links, each
at 256 kbit/s.
The description of the GCI bus is
available in separate documents.
Details are provided in chapter 6.
Fig. 4.2 : Frame Structure GCI
Interface
4.6.1 The Physical Organization
of the GCI Bus
The bus has a clock and a frame
signal for timing, and two data lines
(one for each direction).
In the TE mode, the clock and frame
are generated by the MTC-20172
SIC. Then the timing is slaved to the
S-bus and the network.
In the LT-T, the LT-S or the NT mode,
the MTC-20172 SIC receives timing
from the GCI interface.
In the LT-T, the MTC-20172 SIC must
handle jitter, wander and slip between
the GCI timing and the received S-bus
clock.
The actual timing and speed of these
4 signals exists in several flavours and
variants. The MTC-20172 SIC
performs all the different timing
variants of the V*, IOM1™ and
IOM2™.
15
MTC-20172
Data Sheet & Reference Manual
Rev. 1.1 February 1997
4.6.2 General Content of the
GCI Bus
The GCI interface is organized with 4
channels at 64 kbit/s: B1, B2, M
(Maintenance or Monitor), and B1*
channel; Figure 4.2.
The B1 and B2 channels are
transparent, switched at 64 kbit/s.
In ISDN applications, the B1* channel
contains two D-channel bits, a 4 bits
C/I ‘command/indication’ channel
with the commands (towards MTC-
20172 SIC) or the indications (from
MTC-20172 SIC), and two extra bits
(MR and MX) to control the M-channel.
For details, please see chapter 6.
The D-channel contains HDLC-formatted
messages. It is transported transparently
(NT) or terminated by an HDLC
transceiver (LT-S/LT-T/TE). In the TE/LT-
T, a D-channel access protocol exists
for the S-bus, which is controlled by the
MTC-20172 SIC, and responded to by
the HDLC transmitter. Via the
command/indication (C/I) channel,
commands to and status indications
from the MTC-20172 SIC are
exchanged with a control element
(usually, a µ-controller) or with an other
uplink or downlink ISDN circuit.
Commands and indications are
debounced to avoid erroneous
behaviour.