mt8981dl Mitel, mt8981dl Datasheet - Page 7

• Manufacturer Part Number: mt8981dl
• Description: Iso-cmos St-bus ?amily Digital Switch
• Manufacturer: Mitel

If bit 6 of the Control Register is 0, then bits 2 and 0
of each Connection Memory High location function
normally (see Fig. 5). If bit 2 is 1, the associated ST-
BUS output channel is in Message Mode; i.e., the
byte in the corresponding Connection Memory Low
location is transmitted on the stream at that channel.
Otherwise, one of the bytes received on the serial
inputs is transmitted and the contents of the
Connection Memory Low define the ST-BUS input
stream and channel where the byte is to be found
(see Fig. 6).
If the ODE pin is low, then all serial outputs are high-
impedance.
Register is 1, then all outputs are active. If the ODE
pin is high and bit 6 in the Control Register is 0, then
the bit 0 in the Connection Memory High location
enables the output drivers for the corresponding
individual ST-BUS output stream and channel. Bit
0=1 enables the driver and bit 0=0 disables it (see
Fig. 5).
Applications
Use in a Simple Digital Switching System
Fig. 7 and 8 show how MT8981s can be used with
MT8964s to form a simple digital switching system.
Fig. 7 shows the interface between the MT8981s and
the filter/codecs. Fig. 8 shows the position of these
components in an example architecture.
Figure 7 - Example of Typical Interface between 8981s and 8964s for Simple Digital Switching System
8981 used
control and
in message
8981 used
signalling
If it is high and bit 6 in the Control
mode for
speech
switch
as
MT8981
MT8981
STo0
STi0
STo0
STi0
The MT8964 filter/codec in Fig. 7 receives and
transmits digitised voice signals on the ST-BUS input
D
signals are routed to the ST-BUS inputs and outputs
on the top MT8981, which is used as a digital speech
switch.
The MT8964 is controlled by the ST-BUS input D
originating
generates the appropriate signals from an output
channel in Message Mode.
optimises 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 MT8981.
Fig. 8 shows how a simple digital switching system
may be designed using the ST-BUS architecture.
This is a private telephone network with 128
extensions which uses a single MT8981 as a speech
switch and a second MT8981 for communication with
the line interface circuits.
A larger digital switching system may be designed by
cascading a number of MT8981s. Fig. 9 shows how
four MT8981s 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.
R
, and ST-BUS output D
Line Interface Circuit with 8964 Filter/Codec
D
D
D
R
C
X
from
Filter/Codec
Signalling
MT8964
ISO-CMOS
Logic
the
bottom
X
, respectively.
Line Driver
Converter
2- to 4-
Wire
and
This architecture
MT8981,
MT8981D
These
which
2-23
C