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Description of Operation
10-18
ADSP-BF537 Blackfin Processor Hardware Reference
the slave and accepts new data from the master into its shift register, while
it transmits requested data out of the shift register through its SPI trans-
mit data pin. Multiple processors can take turns being the master device,
as can other microcontrollers or microprocessors. One master device can
also simultaneously shift data into multiple slaves (known as broadcast
mode). However, only one slave may drive its output to write data back to
the master at any given time. This must be enforced in broadcast mode,
where several slaves can be selected to receive data from the master, but
only one slave at a time can be enabled to send data back to the master.
In a multimaster or multidevice environment where multiple processors
are connected via their SPI ports, all
MOSI
pins are connected together, all
MISO
pins are connected together, and all
SCK
pins are connected together.
For a multislave environment, the processor can make use of seven pro-
grammable flags that are dedicated SPI slave select signals for the SPI slave
devices. See
.
L
At reset, the SPI is disabled and configured as a slave.
SPI Control
The
SPI_CTL
register is used to configure and enable the SPI system. This
register is used to enable the SPI interface, select the device as a master or
slave, and determine the data transfer format and word size.
The term “word” refers to a single data transfer of either 8 bits or 16 bits,
depending on the word length (
SIZE
) bit in
SPI_CTL
. There are two special
bits which can also be modified by the hardware:
SPE
and
MSTR
.
The
TIMOD
field is used to specify the action that initiates transfers to/from
the receive/transmit buffers. When set to 00, a SPI port transaction is
begun when the receive buffer is read. Data from the first read will need to
be discarded since the read is needed to initiate the first SPI port transac-
tion. When set to 01, the transaction is initiated when the transmit buffer
is written. A value of 10 selects DMA receive mode and the first
Содержание Blackfin ADSP-BF537
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Страница 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
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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 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...