Texas Instruments MSP53C391, User Manual

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MSP53C391 Timing Waveforms
D-3 MSP53C391/392 Timing Considerations
D.2 MSP53C391 Timing Waveforms
The following waveforms have been found to provide good synthesis results
with a variety of data.
The master microprocessor transfers data to the MSP53C391 slave code
through 4 bit interface. The master microprocessor also samples two of the
data lines to determine the status of the slave. The detailed description about
how to transfer data and read back the status of the slave is described in chap-
ter 2. The typical range of the read strobe pulse is 1
µ
s – 3
µ
s and the same
for write strobe pulse is 1
µ
s – 2
µ
s. It is advisable to restrict the strobe pulse
widths within the recommended range. The typical range of timing between
the rising edge of a read pulse and the falling edge of a write pulse if the slave
is not busy is 19
µ
s – 22
µ
s. Since the slave expects data from the master in
bursts to fill up the buffer, the lower limit of this part of the specification could
be less than 19
µ
s but it is advisable not to stretch the higher limit. The typical
range of timing between the rising edge of the write strobe pulse and the falling
edge of the read strobe pulse if the slave is not busy is 30
µ
s – 34
µ
s. The typi-
cal range of timing between the rising edge of the read strobe pulse and the
falling edge of the write strobe pulse if the slave is busy is 38
µ
s – 58
µ
s. This
timing could be stretched depending upon the synthesis algorithm, but polling
the slave too frequently if the slave is busy would unnecessarily waste time-
critical instruction cycles in the MSP53C391 which might affect the quality of
the speech. At the same time, polling the slave less frequently would lengthen
the response time of the master when the slave needs speech data, which
might eventually lead into the exhaustion of the buffer for the new and re-
freshed speech data.
If the slave is not busy
Read Strobe
Write Strobe Read Strobe
1 – 3
µ
s
19 or less – 22
µ
s
1 – 2
µ
s
30 – 34
µ
s
1 – 3
µ
s
If the slave is busy
38 – 58
µ
s
Read Strobe
Read Strobe
1 – 3
µ
s
1 – 3
µ
s 1 – 3
µ
s
Read Strobe
38 – 58
µ
s