MT9196 Mitel Semiconductor, MT9196 Datasheet - Page 4

• Manufacturer Part Number: MT9196
• Description: Integrated Digital Phone Circuit (IDPC)
• Manufacturer: Mitel Semiconductor

MT9196
Overview
The functional block diagram of Figure 1 depicts the
main operations performed by the MT9196 IDPC.
Each of these functional blocks will be described
individually in the sections to follow. This overview
will describe some of the end-user features which
may be implemented as a direct result of the level of
integration found within the IDPC.
The main feature required of a digital telephone is to
convert the digital Pulse Code Modulated (PCM)
information, being received by the telephone set, into
an analog electrical signal. This signal is then
applied to an appropriate audio transducer such that
the information is finally converted into intelligible
acoustic energy. The same is true of the reverse
direction where acoustic energy is converted first
into an electrical analog and then digitized (into
PCM) before being transmitted from the set. Along
the way if the signals can be manipulated, either in
the analog or the digital domains, other features
such as gain control and signal generation may be
added. Finally, most electro-acoustic transducers
(loudspeakers) require a large amount of power if
they are to develop an acoustic signal. The inclusion
of audio amplifiers to provide this power is required.
The IDPC features complete Analog/Digital and
Digital/Analog conversion of audio signals (Filter/
CODEC) and an analog interface to electro-acoustic
devices (Transducer Interface). Full programmability
of the receive path and side-tone gains is available
to set comfortable listening levels for the user.
Transmit path gain control is available for setting
nominal transmit levels into the network. A digital,
anti-feedback circuit permits both the handset
microphone and the speaker-phone speaker to be
enabled at the same time for group listening
applications.
total loop gain there by preventing a singing
condition from developing.
Signalling in digital telephone systems, behind the
PBX or standard ISDN applications, is handled on
the D-channel and generally does not require DTMF
tones. Locally generated tones, in the set, however,
can be used to provided “comfort tones” or “key
confirmation” to the user, similar to the familiar
DTMF tones generated by conventional phones
during initial call set-up. Also, as the network slowly
evolves from the dial pulse/DTMF methods to the D-
Channel protocols it is essential that the older
methods be available for backward compatibility. As
an example, once a call has been established (i.e.,
from your office to your home) using the D-Channel
Intel® and MCS-51® are registered trademarks of Intel Corporation
Motorola® and SPI® are registered trademarks of Motorola Corporation
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7-130
This anti-feedback circuit limits the
signalling protocol it may be necessary to use in-
band DTMF signalling to manipulate your personal
answering machine in order to retrieve messages.
Thus the locally generated tones must be of network
quality. The IDPC can generate the required tone
pairs as well as single tones to accommodate any in-
band signalling requirement.
Each of the programmable parameters within the
functional blocks is accessed through a serial
microcontroller port compatible with Intel MCS-51
Motorola
Microwire
Functional Description
In this section each of the functional blocks within
IDPC is described along with all of the associated
control/status bits. Each time a control/status bit(s) is
described it is followed by the address register
where it will be found. The reader is referred to the
section titled 'Register Summary' for a complete
listing of all address registers, the control/status bits
associated with each register and a definition of the
function of each control/status bit. The Register
Summary is useful for future reference of control/
status bits without the need to locate them in the text
of the functional descriptions.
Filter/CODEC
The Filter/CODEC block implements conversion of
the analog 3.3 kHz speech signals to/from the digital
domain compatible with 64 kb/s PCM B-Channels.
Selection of companding curves and digital code
assignment are register programmable. These are
CCITT G.711 A-law or
Alternate
Magnitude coding, respectively. Optionally, sign-
magnitude
proprietary applications.
The Filter/CODEC block also implements transmit
and receive audio path gains in the analog domain.
These gains are in addition to the digital gain pad
section and provide an overall path gain resolution of
1.0dB. A programmable gain, voice side-tone path is
also included to provide proportional transmit speech
feedback to the handset receiver. Figure 3 depicts
the nominal half-channel and side-tone gains for the
IDPC.
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