MT92220BG Zarlink Semiconductor, MT92220BG Datasheet - Page 144

• Manufacturer Part Number: MT92220BG
• Description: Description = 1023 Channel Voice Over IP/AAL2 Processor ;; Package Type = Epbga ;; No. Of Pins = 608
• Manufacturer: Zarlink Semiconductor

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10.2
When interfacing with external compression or silence suppression agents in xxPCM, the MT92220 uses special
data formats that allow it to pass more than payload information over the H.110 bus. When receiving ADPCM data,
the position of the highest ‘1’ in the data sample indicates the type of compression used: in this way, all ADPCM
compression types can be encoded within a single payload byte. In addition, the 00h code is used to indicate a
suppression decision. All of this information is coded within an 8-bit sample. The ADCPM sample may also be
contained in the high bits of the byte: in this case, the decoding is reversed, the position of the lowest ‘1’ in the data
sample indicates the compression type.
However, when the received data is ADPCM and silence suppression is being performed, the MT92220 is
incapable of extracting the energy level of the silence from the ADPCM samples. Therefore, the magnitude of the
original PCM value must be transmitted somehow to the MT92220. This is done on an associated stream, so a
single sample of an xxPCM channel now occupies 2 H.110 TSSTs.
When the compression type can be PCM or ADPCM, then an extra indication is necessary to indicate this
compression type. Because the magnitude of the original PCM value is 7 bits, there is a single free bit left on the
associated stream: this bit will be used to indicate if the compression of the current data is PCM or ADPCM. The
remaining encoding of the data is done in the same way.
In summary, single time-slot mode allows:
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Dual time-slot mode allows:
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PCM samples with internal VAD for silence suppression and energy level detection.
ADPCM samples with compression auto-detection
ADPCM samples with compression auto-detection and silence suppression but no energy level detection.
The CN packet will have to be programmed through the CPU interface.
PCM and ADPCM samples with compression auto-detection
ADPCM samples with compression auto-detection and silence suppression with energy level detection.
PCM and ADPCM samples with compression auto-detection and silence suppression with energy level
detection.
TX TDM Data Formats
Zarlink Semiconductor Inc.