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ADSP-BF537 Blackfin Processor Hardware Reference
10-19
SPI Compatible Port Controllers
transaction is initiated by enabling the SPI for DMA receive mode. Subse-
quent individual transactions are initiated by a DMA read of the
SPI_RDBR
. A value of 11 selects DMA transmit mode and the transaction is
initiated by a DMA write of the
SPI_TDBR
.
The
PSSE
bit is used to enable the
SPISS
input for master. When not used,
SPISS
can be disabled, freeing up a chip pin as general-purpose I/O.
The
EMISO
bit enables the
MISO
pin as an output. This is needed in an
environment where the master wishes to transmit to various slaves at one
time (broadcast). Only one slave is allowed to transmit data back to the
master. Except for the slave from whom the master wishes to receive, all
other slaves should have this bit cleared.
The
SPE
and
MSTR
bits can be modified by hardware when the
MODF
bit of
the
SPI_STAT
register is set. See
.
provides the bit descriptions for
SPI_CTL
.
Clock Signals
The
SCK
signal is a gated clock that is only active during data transfers for
the duration of the transferred word. The number of active edges is equal
to the number of bits driven on the data lines. The clock rate can be as
high as one-fourth of the
SCLK
rate. For master devices, the clock rate is
determined by the 16-bit value of
SPI_BAUD
. For slave devices, the value in
SPI_BAUD
is ignored. When the SPI device is a master,
SCK
is an output sig-
nal. When the SPI is a slave,
SCK
is an input signal. Slave devices ignore
the serial clock if the slave select input is driven inactive (high).
The
SCK
signal is used to shift out and shift in the data driven onto the
MISO
and
MOSI
lines. The data is always shifted out on one edge of the
clock (the active edge) and sampled on the opposite edge of the clock (the
sampling edge). Clock polarity and clock phase relative to data are pro-
grammable into
SPI_CTL
and define the transfer format.
Содержание Blackfin ADSP-BF537
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Страница 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
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Страница 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
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Страница 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...