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Description
The Quad ADPCM Transcoder is a low power,
CMOS device capable of four encode and four
decode functions per frame. Four 64 kbit/s PCM
octets are compressed into four 32, 24 or 16 kbit/s
ADPCM words, and four 32, 24 or 16 kbit/s ADPCM
words are expanded into four 64 kbit/s PCM octets.
The 32, 24 and 16 kbit/s ADPCM transcoding
algorithms
utilized
conform
to
ITU-T
Recommendation G.726 (excluding 40 kbit/s), and
ANSI T1.303 - 1989.
Switching, on-the-fly, between 32 kbit/s and 24 kbit/s
ADPCM, is possible by controlling the appropriate
mode select (MS1 - MS6) control pins. All optional
functions of the device are pin selectable allowing a
simple interface to industry standard codecs, digital
phone devices and Layer 1 transceivers. Linear
coded PCM is provided to facilitate external DSP
functions .
Applications
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Pair gain
Voice mail systems
Wireless telephony systems
ADPCMi
ADPCMo
ADPCM
I/O
Full Duplex
Quad
Transcoder
PCM
I/O
PCMo1
PCMi1
PCMo2
PCMi2
ENB1
ENB2/F0od
BCLK
F0i
MCLK
C2o
EN1
EN2
Timing
Control Decode
VDD VSS PWRDN IC
MS1 MS2 MS3 A/碌 FORMAT MS4 MS5 MS6 LINEAR SEL
Figure 1 - Functional Block Diagram
8-33
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