Master Microprocessor Interface Description
2-5
MSP53C391 Hardware Description
Read Operation
1) The master microprocessor sets R/W high to indicate a read operation.
2) The master microprocessor sets STROB to low and reads the state of
BUSY and EOS.
3) The master microprocessor sets STROB high.
If the BUSY signal was high in step 2, the MSP53C391 is
not busy and is
ready to accept a write operation. If the BUSY signal was low in step 2, the
MSP53C391 is
not ready to accept a write operation and the read operation
should be repeated until BUSY is asserted high.
If EOS was high in step 2, the synthesis process has reached the end of the
speech data stream. In this case, the master microprocessor should stop try-
ing to send data and reset the MSP53C391 to allow it to accept additional com-
mands or synthesis data.
The frequency of the polling operation should be optimized to the data rate of
the algorithm being used to synthesize speech. If the polling operation is too
frequent, the MSP53C391 spends too much time servicing the polling opera-
tion and the quality of the synthetic speech may be affected. If the polling op-
eration is too infrequent, the internal buffer may run out of data and the synthe-
sis process can become corrupted. Normally, a polling frequency of four times
the bit rates of the speech data provides optimal transfer characteristics.
Example:
For 6.2 kbps CELP the frequency of polling would be
6.2
n
4
n = the number of bits transfered at a time
Write Operation
1) The master processor should determine that the MSP53C391 is ready to
accept data by reading the BUSY signal as described previously.
2) The master microprocessor clears R/W low to indicate a write operation
3) The master microprocessor presents valid data to the four data pins
(DATA0 – DATA3).
4) The master microprocessor pulses the STROB signal low and then high
to latch the data to the MSP53C391 input data latch.
5) The master microprocessor should do a read operation to determine that
the MSP53C391 is ready to accept additional data before attempting to
write more data.
Содержание MSP53C391
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Страница 98: ...F 1 Appendix A MSP53C391 and MSP53C392 Data Sheet Topic Page F 1 MSP53C391 MSP53C392 F 2 Appendix F ...
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