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ADSP-BF537 Blackfin Processor Hardware Reference
10-17
SPI Compatible Port Controllers
SPI General Operation
The SPI can be used in a single master as well as multimaster environ-
ment. The
MOSI
,
MISO
, and the
SCK
signals are all tied together in both
configurations. SPI transmission and reception are always enabled simul-
taneously, unless the broadcast mode has been selected. In broadcast
mode, several slaves can be enabled to receive, but only one of the slaves
must be in transmit mode driving the
MISO
line. If the transmit or receive
is not needed, it can simply be ignored. This section describes the clock
signals, SPI operation as a master and as a slave, and error generation.
Precautions must be taken to avoid data corruption when changing the
SPI module configuration. The configuration must not be changed during
a data transfer. The clock polarity should only be changed when no slaves
are selected. An exception to this is when an SPI communication link con-
sists of a single master and a single slave,
CPHA = 1
, and the slave select
input of the slave is always tied low. In this case, the slave is always
selected and data corruption can be avoided by enabling the slave only
after both the master and slave devices are configured.
In a multimaster or multislave SPI system, the data output pins (
MOSI
and
MISO
) can be configured to behave as open drain outputs, which prevents
contention and possible damage to pin drivers. An external pull-up resis-
tor is required on both the
MOSI
and
MISO
pins when this option is
selected.
The
WOM
bit controls this option. When
WOM
is set and the SPI is config-
ured as a master, the
MOSI
pin is three-stated when the data driven out on
MOSI
is a logic high. The
MOSI
pin is not three-stated when the driven data
is a logic low. Similarly, when
WOM
is set and the SPI is configured as a
slave, the
MISO
pin is three-stated if the data driven out on
MISO
is a logic
high.
During SPI data transfers, one SPI device acts as the SPI link master,
where it controls the data flow by generating the SPI serial clock and
asserting the SPI device select signal (
SPISS
). The other SPI device acts as
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 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 ...