PEB2445NV1.2 Lantiq, PEB2445NV1.2 Datasheet - Page 25

• Manufacturer Part Number: PEB2445NV1.2
• Manufacturer: Lantiq

Specifications of PEB2445NV1.2

• Lead Free Status / Rohs Status: Supplier Unconfirmed

PEB 2445
Functional Description
stored in the CCM include the input time-slot and line number, the associated
conference number as well as the noise suppression thresholds and the attenuation
levels. The conference number defines a unique location in the Conference Sum
Memory (CSM) used to store the accumulated samples for each conference. The
Conference Sum Memory is alternately loaded in the first half of the frame and unloaded
in the following second half. In the first half the input samples are processed to
implement the noise suppression, the expansion according to the European A-law or the
US -law and the attenuation function. The Data Memory (DM) buffers these samples
for output processing. The CSM is used to accumulate these samples and store the
resulting sum. During output processing the input sample is retrieved from the Data
Memory and the appropriate sum from the Conference Sum Memory for subtraction, so
that the channel output signal contains the contribution of all the other channels in the
conference except its own. After output attenuation and PCM compression, the data are
written in the Speech Memory for output switching.
If one result of the subtractions exceeds the full scale value, a saturation appears and
the MUSAC-A signals this conference overflow condition by an interrupt. The conference
number of the conference in overflow is buffered in the Conference Status Register
(CST) which can be retrieved by the external controller.
A tone to be inserted into a conference is handled as an additional conference
subscriber using any input PCM channel (access to CCM) but without assigning an
output time-slot (no access to CM).
Multipoint Switching is a special form of conferencing for data communication. In the
multipoint switching mode several terminals are connected together. Normally only one
should transmit at a time; its signal is distributed to the other terminals. For collision
detection purposes all input signals are summed up to construct the output signal. In
contrast to audio conferences terminals broadcast data to the MUSAC-A which are only
‘or-connected’. That is, at each bit time, the ‘conference sum’ is ‘1’ if the input of one or
more terminals is ‘1’; otherwise, the result is ‘0’. The data memory, the subtractor, the
linearization and attenuation are of no use in this mode. The general procedure is the
same as for conferencing.
All attenuations of the PCM values are calculated by the following mechanism
1. Expansion according CCITT Rec. G. 711
2. Attenuation by
– (x/6)
lin. value
2
, x = Attenuation
3. Comparison according CCITT Rec. G. 711
These functions are implemented by a PLA/ROM.
The chip architecture makes it possible to decrease the delay between incoming and
outgoing PCM channels. The processed input samples are transmitted either in the
same frame or in the next frame at the latest.
Semiconductor Group
25
02.96