m34116 STMicroelectronics, m34116 Datasheet - Page 8

• Manufacturer Part Number: m34116
• Description: Pcm Conference Call And Tone Generation Circuit
• Manufacturer: STMicroelectronics

M34116
CIRCUIT DESCRIPTION
ALGORITHMS
ARCHITECTURE
The basic time slot (16 periods of the master
clock) is divided in four different parts that per-
form four different operations (also refer to Fig. 2
block diagram):
# input processing: attenuation or gain of input
# conference addition: the above PCM signal,
# conference subtraction: the signal stored in the
# output processing: attenuation or gain of the
8/23
Conference. For each channel, the PCM signal
Attenuation gain. The PCM signal is converted
coming in is added to its conference and the
PCM signal of the previous frame is subtracted
to its conference before being sent out. The
output signal contains only the data of all the
other channels in its conference except its
own.
Tone. A fourth of a sine wave equivalent to
3.9Hz (8KHz/2048) is stored in a ROM which is
read at multiple of the step (modulus 512)
equivalent to the specified frequency. This step
is used until the duration is reached then a
new step will be used according to the speci-
fied sequence.
to logarithmic of the equivalent linear and then
added or subtracted to the specified level. It is
then raised to the power of 10 to be converted
back to linear.
PCM according to the algorithm mentioned
earlier. The serial PCM signal coming in is
loaded as 8 bits parallel and converted to loga-
rithmic of the linear (through the PCM to LOG
LIN block). It is then added to the attenuation
or gain levels (also in logarithmic) stored in the
MPU interface, the result is raised to the power
of 10 (through the POWER 10 block) to be
converted back to linear and written in the
FRAME RAM.
amplified or attenuated and converted in linear,
is added to the conference and the result is
stored in the conference RAM (block CONF
RAM).
FRAME RAM during the previous frame is sub-
tracted to the conference and the result is
stored in the conference RAM.
PCM to be sent out. The result of the above
substraction is converted to PCM (through the
block LIN to PCM) and to logarithmic (through
the block PCM to LOG LIN), added to the at-
tenuation or gain level stored in the MPU inter-
face, converted to linear (through the block
POWER 10) and then to PCM (through the
block LIN to PCM). The resulting 8 bits are
then shifted out serially.
If a channel is in conference, then all the four
above operations are applied. If it is in transpar-
ent mode, then only the first and last operations
are applied. For tone generation, the two first op-
erations are not used. During the third part, the
tone ROM is read. Since the ROM data is in lin-
ear it can therefore be applied to the fourth opera-
tion for output processing.
By default, after reset, the M34116 has the func-
tionality and the instruction set of the M116. With
a new operating mode instruction, the user can
select the functionality of the M34116 with its new
instruction set. The instruction set includes:
transparent connection: the user specifies which
conference connection: the user specifies which
operating mode: the user can choose either the
channel disconnection: the user specifies which
overflow status. The user specifies which of the
channel status. The user specifies the channel
M116 mode or the M34116 mode, the PCM
byte format (no bit inverted, even bit inverted,
odd bit inverted or all bit inverted) and the
presence or not of the extra bit.
channel to be connected to which conference
with the attenuationor gain levels to be applied
to the PCM signal coming in and/or sent out.
channel to be connected in transparent mode
(bypass mode) with the attenuation or gain lev-
els to be applied to the PCM signal coming in
and/or sent out.
channel the tone must be sent out with the at-
tenuation or gain levels and the tone se-
quence. The sequence is composed of maxi-
mum 4 pairs of frequency-duration for tone and
maximum 32 pairs of frequency-duration for
melody. The frequency range is 3.9Hz to
3938Hz and the duration range is from 32ms
to 8610ms. The user can specify either all of
the pairs or finish the sequence with the byte
hex FF. The M34116 will loop the specified se-
quence endlessly or until the channel is dis-
connected. The melody could be either a sine
or square wave (pin programmable).
channel to be disconnected. A disconnected
channel can be reconnected only after a mini-
mum of one frame time.
4 banks of 8 conferences to be monitored and
the M34116 will send the status byte at the
read operation.
number and the M34116 will send out the
status bytes at the read operation. These bytes
include: conference number or transparent
mode or tone or no connection, input attenu-
ation or gain levels, output attenuation or gain
levels. If the channel is in the tone mode, the
tone sequence of frequency and duration will
also be sent out.
tone generation: the user specifies to which