
Operating Modes
15-14
ADSP-214xx SHARC Processor Hardware Reference
SPI Modes
The SPI supports four different combinations of serial clock phases and
polarity called SPI modes. The application code can select any of these
combinations using the
CLKPL
and
CPHASE
bits (10 and 11).
shows the transfer format when
CPHASE
= 0 and
shows the transfer format when
CPHASE
= 1.
Each diagram shows two waveforms for
SPICLK
—one for
CLKPL
= 0 and
the other for
CLKPL
= 1. The diagrams may be interpreted as master or
slave timing diagrams since the
SPICLK
,
MISO
, and
MOSI
pins are directly
connected between the master and the slave. The
MISO
signal is the output
from the slave (slave transmission), and the
MOSI
signal is the output from
the master (master transmission).
The
SPICLK
signal is generated by the master, and the
SPIDS
signal repre-
sents the slave device select input to the processor from the SPI master.
The diagrams represent 8-bit transfers (
WL
= 0) with MSB first (
MSBF
= 1).
Any combination of the
WL
and
MSBF
bits of the
SPICTL
register is allowed.
For example, a 16-bit transfer with the LSB first is one possible
configuration.
The clock polarity and the clock phase should be identical for the master
device and slave devices involved in the communication link. The transfer
format from the master may be changed between transfers to adjust to var-
ious requirements of a slave device.
When
CPHASE
= 0, the slave-select line,
SPIDS
, must be inactive
(
HIGH
) between each word in the transfer. Even in SPI slave mode
when
CPHASE
= 0, the master should de assert the
SPIDS
line
between each transfer. When
CPHASE
= 1,
SPIDS
may either remain
active (
LOW
) between successive transfers or be inactive (
HIGH
).
shows the SPI transfer protocol for
CPHASE
= 0. Note that
SPICLK
starts toggling in the middle of the data transfer where the bit set-
tings are
WL
= 0, and
MSBF
= 1.
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Summary of Contents for SHARC ADSP-214 Series
Page 60: ...Contents lx ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Page 72: ...Notation Conventions lxxii ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Page 130: ...Programming Model 2 52 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Page 264: ...Programming Models 3 134 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Page 290: ...Programming Model 4 26 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Page 296: ...Programming Model 5 6 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Page 396: ...Effect Latency 7 28 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Page 520: ...Programming Model 10 62 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Page 616: ...Debug Features 14 22 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Page 656: ...Programming Model 15 40 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Page 714: ...Programming Model 19 10 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Page 1132: ...Register Listing A 306 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Page 1192: ...Index I 34 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...