®
CMOS
MT9125
Dual ADPCM Transcoder
Preliminary Information
Features
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Dual channel full duplex transcoder
32 kbit/s and 24 kbit/s ADPCM coding,
compatible to G.721 & and G.723 (1988) and
ANSI T1.303-1989
Low power operation, total 25mW typical
Asynchronous 4.096 MHz master clock
operation
Transparent ADPCM bypass capability
Serial interface for both PCM and ADPCM data
streams
ST-BUS interface supported
Pin selected µ-law or A-law operation
Pin selected CCITT or sign-magnitude PCM
coding
Single 5 volt power supply
Optional reset value (CCITT Table 3/G.721)
capability
ISSUE 3
August 1993
Ordering Information
MT9125AE
MT9125AP
24 Pin Plastic DIP
28 Pin PLCC
-40 to +85°C
Description
The Dual-channel ADPCM transcoder is a low
power, CMOS device capable of two encoder
functions and two decoder functions. Two 64 kbit/s
PCM channels are compressed into two 32 kbit/s
ADPCM channels, and two 32 kbit/s ADPCM
channels are expanded into two 64 kbit/s PCM
channels.
The 32 kbit/s ADPCM transcoding
algorithm utilized conforms to CCITT Recom-
mendation G.721 and ANSI T1.303-1989.
The
device also supports a 24 kbit/s (three bit word)
algorithm (CCITT/G.723).
Switching, on-the-fly, between 32 kbit/s and 24
kbit/s, is possible by toggling the appropriate Mode
Select (MS1-MS4) control pins.
Applications
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Pair gain
Voice mail systems
Wireless set base stations
C2o
BCLK
F0i
MCLK
ENS
ST-BUS
Converter
EN2
Timing
EN1
DSTo
ADPCMi
ADPCM
I/O
ADPCMo
ENA
Control Decode
Transcoder 1
PCM
I/O
DSTi
ENB1
ENB2
Transcoder 2
VDD
VSS
PWRDN
IC
MS1 MS2
A/µ FORMAT
MS3 MS4
Figure 1 - Functional Block Diagram
8-17
MITEL [ MITEL NETWORKS CORPORATION ]
