M34116 datasheet(8/23 Pages) STMICROELECTRONICS

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CIRCUIT DESCRIPTION

ALGORITHMS

♦ Conference. For each channel, the PCM signal

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.

♦ Attenuation gain. The PCM signal is converted

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.

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

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.

# conference addition: the above PCM signal,

amplified or attenuated and converted in linear,

is added to the conference and the result is

stored in the conference RAM (block CONF

RAM).

# conference subtraction: the signal stored in the

FRAME RAM during the previous frame is sub-

tracted to the conference and the result is

stored in the conference RAM.

# output processing: attenuation or gain of the

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:

◊ operating mode: the user can choose either the

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.

◊ conference connection: the user specifies which

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.

◊ transparent connection: the user specifies which

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.

◊ tone generation: the user specifies to which

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).

◊ channeldisconnection: the user specifies which

channel to be disconnected. A disconnected

channel can be reconnected only after a mini-

mum of one frame time.

◊ overflow status. The user specifies which of the

4 banks of 8 conferences to be monitored and

the M34116 will send the status byte at the

read operation.

◊ channel status. The user specifies the channel

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.

M34116

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