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Sequence of Command Codes and Data Streams
3-3
MSP53C691 Software Description
Note:
Throughout the rest of the chapter it is assumed that data from the
MSP53C691 is always read four nibbles at a time. The MSP53C691 pulls
OUTRDY low when it wants to send a nibble to the master (read from the
MSP53C691). It is also assumed that the data is sent to the MSP53C691
from the master only when the MSP53C691 pulls INRDY low. In four-bit
mode, the DATA4 (DATA/COMMAND) bit is low when a command or its pa-
rameters are written to the MSP53C691, and the DATA4 (DATA/COM-
MAND) bit is high when the speech or FM data is written to the MSP53C691.
While sending speech or command in four-bit mode, the data is always sent
most-significant nibble first and least-significant nibble last.
All commands and their parameters are sent with a four-bit interface. Com-
mands and their parameters are sent to the slave through data lines
DATA0–DATA3 while DATA4 (DATA/COMMAND) line is set low.
The procedures for reading from or writing to the MSP53C691 are described
in the
Hardware Description chapter.
3.3
Sequence of Command Codes and Data Streams
The sequence for sending the command codes and data streams is as follows:
-
The sequence for the command codes consists of a command header, a
level 1, and, sometimes, a level 2 parameter. The command header con-
trols the operation performed by the MSP53C691. Level 1 and level 2 are
two levels of command information that further define the command code.
Each nibble of the command code is sent along with a 0 in the DATA/COM-
MAND line to indicate that it is a command. Refer to section 3.3.2,
Parame-
ters and Table 3–1, Command Codes for additional information.
-
Data streams are speech data sent to the MSP53C691 from speech files
processed by the SDS6000 (see Appendix C for details). Each nibble of
the speech data is sent along with a 1 on the DATA/COMMAND line to indi-
cate that it is speech data.
3.3.1
Command Header
The command header is the first information of the command code sequence
sent to the MSP53C691. The command header controls the operation being
performed by the MSP53C691. The MSP53C691 recognizes the following
command headers:
-
Command header 1—Configure internal registers
-
Command header 2—Set/Clear I/O ports PD4 through PD7
-
Command header 3—Read contents of I/O ports
-
Command header 4—Start speaking
-
Command header 5—Stop speaking
Summary of Contents for MSP53C691
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