AMBE-2000 Digital Voice Systems, Inc., AMBE-2000 Datasheet - Page 54

• Manufacturer Part Number: AMBE-2000
• Description: 2.0 - 9.6 KBPS Single ic For Toll-quality, Low Data Rate, Real Time Speech Compression
• Manufacturer: Digital Voice Systems, Inc.

8.3
The Analog Devices AD73311 codec chip presents a simple low cost solution for use with DVSI’s AMBE-2000™
Vocoder chip. This application note provides information on alternative methods of interfacing these components.
AD73311 Codec (using a 3 volt supply)
It may be desirable for the AD73311 AD/DA converter to be configured for a 3-volt supply voltage instead of a 5-
volt supply voltage. The diagram and configuration procedure below outline the details necessary in order to send
alternate configuration words to the CODEC.
Figure 2: The AMBE-2000™ with the AD73311 Configured for 3-volt operation.
The objective of this circuit is to tri-state the output of the AMBE-2000™ CODEC_TX_DATA. This allows the
DSP or Microcontroller to communicate with the AD73311 to send it the desired configuration.
Configure the AMBE-2000™ for operation with the AD73311 Codec. Set the CODEC_SEL pins as shown.
Hold the CODEC_TX_DATA lines on the AMBE-2000™ in tri-state (in the circuit set the SDI bit to 0,b) during
power up.
While the AMBE-2000™ lines are in tri-state, send the desired configuration words from the
DSP/Microcontroller/logic to the AD73311 (Reset timing constraints for the AD73311 must be met).
After sending the configuration words set the SDI Control bit to 1,b (SEE NOTE). This sets the CODEC SDI line
for normal operation with the AMBE-2000™.
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DSP/Microcontroller
U1
U3
CODEC_RX_STRB
CODEC_RX_DATA
CODEC_TX_STRB
CODEC_TX_DATA
AMBE-2000
CODEC_RX_CLK
CODEC_TX_CLK
Configuring the AD73311 for 3-Volt Operation
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SCLK
SDO
FS
CODEC_SEL [1-0] (pins 85,84) = 01,b
27
33
37
29
31
41
2
2
U4A
SN74AHC125
SN74AHC125
U5A
3
3
14
17
18
16
19
SCLK
SDOFS
SDIFS
SDO
SDI
U2
AD73311AR
AVDD1
AVDD2
DVDD
2
MCLK
U8A
SE
20
15
3
9
12
1
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High
16.384 MHz
3.3
Volts
3.3 Volts
SDI
CONTROL
0/DSP
1/AMBE-2000