Description of the Command Codes
3-25
MSP53C691 Software Description
10) The MSP53C691 starts playing FM after the buffer is filled (that is, the first
24 (decimal) bytes from the file has been received). The MSP53C691 still
continues to pull INRDY low and waits for speech data or command from
the master. The master can either send a valid command or send CELP/
MELP speech data.
11) When the MSP53C691 needs more FM data, it pulls OUTRDY low to send
a nibble back to the master. The master must read the nibble from the bus.
The MSP53C691 sends a total of four nibbles to the master by pulling
OUTRDY low three more times and the master must read the four nibbles
as previously described in step 7. The four nibbles sent this time are 0, X,
2, and 3. X is the number of FM data bytes requested by the MSP53C691.
The 2 and 3 indicate a request for FM data.
Most Significant
DATA LINES
DATA3
DATA2
DATA1
DATA0
0
0
0
0
First nibble sent
X
X
X
X
Second nibble sent
0
0
1
0
Third nibble sent
Least Significant
0
0
1
1
Fourth nibble sent
12) The MSP53C691 pulls INRDY low again after sending the four nibbles re-
questing the FM data from the master.
13) In response, the master must send 9 as a command (0x09), letting the
MSP53C691 know that master is going to send FM data.
Most Significant
DATA LINES
DATA4
DATA3
DATA2
DATA1
DATA0
0
1
0
0
1
Command header sent
14) After receiving the command 9, the MSP53C691 lowers INRDY again. In
response, the master must send another nibble as the level 1 parameter,
letting the MSP53C691 know how many bytes of FM data it is going to
send. This number must be less than or equal to the requested number
of FM data by the MSP53C691. For example, the MSP53C691 may re-
quest 8 bytes of data, but the master may wish to send only 6 bytes of FM
data. Therefore, the master sends 0x6 to the MSP53C691.
Most Significant
DATA LINES
DATA4
DATA3
DATA2
DATA1
DATA0
0
X
X
X
X
Level 1 parameter sent
Содержание MSP53C691
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