MT8980D
Applications
Use in a Simple Digital Switching System
Data Sheet
Figs. 7 and 8 show how MT8980s can be used with MT8964s to form a simple digital switching system. Fig. 7
shows the interface between the MT8980s and the filter/codecs. Fig. 8 shows the position of these components in
an example architecture.
The MT8964 filter/codec in Fig. 7 receives and transmits digitized voice signals on the ST-BUS input D
R
, and ST-
BUS output D
X
, respectively. These signals are routed to the ST-BUS inputs and outputs on the top MT8980, which
is used as a digital speech switch.
The MT8964 is controlled by the ST-BUS input D
C
originating from the bottom MT8980, which generates the
appropriate signals from an output channel in Message Mode. This architecture optimizes the messaging capability
of the line circuit by building signalling logic, e.g., for on-off hook detection, which communicates on an ST-BUS
output. This signalling ST-BUS output is monitored by a microprocessor (not shown) through an ST-BUS input on
the bottom MT8980.
Fig. 8 shows how a simple digital switching system may be designed using the ST-BUS architecture. This is a
private telephone network with 256 extensions which uses a single MT8980 as a speech switch and a second
MT8980 for communication with the line interface circuits.
A larger digital switching system may be designed by cascading a number of MT8980s. Fig. 9 shows how four
MT8980s may be arranged in a non-blocking configuration which can switch any channel on any of the ST-BUS
inputs to any channel on the ST-BUS outputs.
STo0
STi0
8980 used
as
speech
switch
MT8980
D
X
D
R
D
C
STo0
STi0
8980 used
in message
mode for
control and
signalling
MT8964
Filter/Codec
Signalling
Logic
Line Driver
and
2- to 4-
Wire
Converter
Line Interface Circuit with 8964 Filter/Codec
MT8980
Figure 7 - Example of Typical Interface between 8980s and 8964s for Simple Digital Switching
System
8
Zarlink Semiconductor Inc.
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
