Software Overview
4-2
4.1
Software Overview
The MSP53C391 and the MSP53C392 are controlled using a formatted com-
munication sequence that passes commands and data from the master micro-
processor to the slave.
4.2
Command Sequence
There are two types of streams that can be sent to the slave.
Data streams transmit speech synthesis data.
Command streams control various features of the slave device such as
volume, the state of the two expansion pins, and other special features.
Each stream consists of:
1) A command header whose purpose is to synchronize the data stream.
2) A command code that indicates which command should be executed or
which synthesis algorithm is to be used to process the data stream.
3) The data stream or optional command parameters.
4) After the termination code in the data stream, four nibbles (MSP53C391)
or four bytes (MSP53C392) of dummy data that resets the processor.
4.3
Command Header
The command header is used to synchronize the data stream between the
master microprocessor and the MSP53C391 or MSP53C392. The command
header is the same for both data streams and command streams, but the com-
mand header used for the MSP53C391 is different from the command header
used for the MSP53C392 because of the different data bus widths.
The command header used for the MSP53C391 is a series of at least 5 nibbles
with all bits set high followed by a 0x0, 0xA sequence. The complete command
header sequence used for the MSP53C391 is therefore: 0xF, 0xF, 0xF, 0xF,
0xF, 0x0, 0xA.
The command header used for the MSP53C392 is a series of at least 5 bytes
with all bits set high followed by a 0x0A sequence. The complete command
header sequence used for the MSP53C392 is therefore: 0xFF, 0xFF, 0xFF,
0xFF, 0FF, 0x0A.
Summary of Contents for MSP53C391
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