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Description of the Command Codes
3-14
The different modes of speaking are described in detail in the following
subsections.
3.5.4.1
Speaking CELP, MELP, ADPCM in Four-Bit Data Transfer Mode
Commands and data are sent over a four-bit interface. When data is sent over
the DATA0 through DATA3 lines, DATA4 (pin 35) becomes the
DATA/COMMAND control line. The DATA/COMMAND line defines whether
the information on DATA0 through DATA3 is data or commands. When DATA0
through DATA3 and DATA/COMMAND bits are received, the MSP53C691
analyzes the DATA/COMMAND bit to determine if the information is data or
commands being received on DATA0 through DATA3 lines.
DATA/COMMAND LINE
DESCRIPTION
Set to 0
Command sent to the MSP53C691
Set to 1
Data sent to the MSP53C691
The following typical sequence of events takes place while playing CELP,
MELP, or ADPCM in four-bit mode:
1) The MSP53C691 pulls INRDY low and waits for a command from the
master.
2) The master sends the command header 0x4 (command header for speak-
ing in four-bit mode) on the data bus. Note that writing 0x04 to the data bus
ensures that the DATA4 line is low, indicating that value on data lines
DATA0–DATA3 is a command.
Most Significant
DATA LINES
DATA4
DATA3
DATA2
DATA1
DATA0
0
0
1
0
0
First command header sent
3) After receiving the header, the MSP53C691 pulls INRDY low again and
waits for the level 1 parameter from the master.
4) The master sends the level 1 command parameter 1 to indicate the four-bit
transfer mode for CELP, MELP, or ADPCM.
Most Significant
DATA LINES
DATA4
DATA3
DATA2
DATA1
DATA0
0
0
0
0
1
Level 1 parameter sent
5) The MSP53C691 interprets the command and initializes itself to get ready
to speak.
6) The MSP53C691 pulls INRDY low, indicating that it is ready to receive
more commands or speech data.
Содержание MSP53C691
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