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SPI Operation Modes
16
2.8
Baud Rate Limitations
It is recommended to operate the master and slave SPIs at the same baud
rate. However, when this is not possible the SPICLK ranges specified in
Table 3
must be followed to ensure proper data transfer. The SPICLK rate is
set by adjusting the PRESCALE value in the SPICTRL1 register.
Table 3.
SPICLK Ranges
In all clocking mode configurations, the slave SPICLK must never be less
than half the speed of the master SPICLK. Doing so may allow the master to
start a new SPI transmission before the slave is ready. When operating with
PHASE = 0, the slave SPICLK must not be more than 1% faster than the
master SPICLK. When operating with PHASE = 1 the slave SPICLK must not
be more than two times faster than the master SPICLK. If the slave SPICLK
exceeds the master SPICLK by more than 1% when PHASE = 0 or by 2x
when PHASE = 1 there is a possibility that the slave will move data from the
input shift register to SPIBUF before the master is finished transferring data.
POLARITY
PHASE
SPICLK RATIO
X
0
%)
X
1
MasterSPICLK
2
-------------------------------------------
SlaveSPICLK
MasterSPICLK
1
+
(
≤
≤
MasterSPICLK
2
-------------------------------------------
SlaveSPICLK
MasterSPICLK
2
×
(
)
≤
≤
Summary of Contents for TMS470R1 series
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