
Interface Overview
13-6
ADSP-BF59x Blackfin Processor Hardware Reference
SPI Slave Select Input Signal (SPISS)
The
SPISS
signal is the SPI slave select input signal. This is an active-low
signal used to enable a processor when it is configured as a slave device.
This input-only pin behaves like a chip select and is provided by the mas-
ter device for the slave devices. For a master device, it can act as an error
signal input in a multimaster environment. In multimaster mode, if the
SPISS
input signal of a master is asserted (driven low), and the
PSSE
bit in
the
SPI_CTL
register is enabled, an error has occurred. This means that
another device is also trying to be the master device.
The enable lead time (T1), the enable lag time (T2), and the sequential
transfer delay time (T3) each must always be greater than or equal to
one-half the
SCK
period. See
Figure 13-3 on page 13-7
. The minimum
time between successive word transfers (T4) is two
SCK
periods. This is
measured from the last active edge of
SCK
of one word to the first active
edge of
SCK
of the next word. This is independent of the configuration of
the SPI (CPHA, MSTR, and so on).
For a master device with
CPHA
= 0, the slave select output is inactive (high)
for at least one-half the
SCK
period. In this case, T1 and T2 will each
always be equal to one-half the
SCK
period.
SPI Slave Select Enable Output Signals
When operating in master mode, Blackfin processors may use any GPIO
pin to enable individual SPI slave devices by software. In addition, the SPI
Figure 13-2. Blackfin Processor as Slave SPI Device
8-BIT HOST
MICROCONTROLLER
BLACKFIN PROCESSOR
SLAVE SPI DEVICE
SCLK
MOSI
MISO
MISO
SCK
MOSI
SPISS
S_SEL
Содержание ADSP-BF59x Blackfin
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Страница 74: ...Processor Specific MMRs 2 10 ADSP BF59x Blackfin Processor Hardware Reference...
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Страница 738: ...Boundary Scan Architecture B 8 ADSP BF59x Blackfin Processor Hardware Reference...