mt8981de1 Zarlink Semiconductor, mt8981de1 Datasheet - Page 8

• Manufacturer Part Number: mt8981de1
• Description: Digital Switch
• Manufacturer: Zarlink Semiconductor

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. If it is high and bit 6 in the Control 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.
The MT8964 filter/codec in Fig. 7 receives and transmits digitized voice signals on the ST-BUS input D
BUS output D
is used as a digital speech switch.
The MT8964 is controlled by the ST-BUS input D
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 MT8981.
Figure 7 - Example of Typical Interface between 8981s and 8964s for Simple Digital Switching
X
8981 used
in message
control and
8981 used
signalling
, respectively. These signals are routed to the ST-BUS inputs and outputs on the top MT8981, which
mode for
speech
switch
as
MT8981
MT8981
STo0
STi0
STo0
STi0
Zarlink Semiconductor Inc.
MT8981D
C
originating from the bottom MT8981, which generates the
System
8
Line Interface Circuit with 8964 Filter/Codec
D
D
D
X
R
C
Filter/Codec
Signalling
MT8964
Logic
Line Driver
Converter
2- to 4-
Wire
and
Data Sheet
R
, and ST-