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SPI Operation Modes
Serial Peripheral Interface (SPI) Module (SPNU195E)
9
2.4
SPI Operation; Five-Pin Option (Hardware Handshaking)
To use the hardware handshaking mechanism, both the SPIENA pin and
SPISCS pin must be configured as functional pins.
In the master SPI (CLKMOD = 1), if the SPIENA pin is configured as a
functional input. If configured as a slave SPI, the SPIENA pin is configured as
a functional output. If the SPIENA pin is in high-z mode (ENABLE_HIGHZ =
1), the slave SPI will put this signal into the high-impedance state if it receives
a new character from the master or if the slave becomes de-selected by the
master (SPISCS goes high). The slave will drive the signal low when new
data is written to the slave shift register (SPIDAT0) and the slave has been
selected by the master (SPISCS is low).
If the SPIENA pin is in push-pull mode (ENABLE_HIGHZ = 0), the slave will
drive SPIENA high only if there is new data in the buffer register and the slave
is selected by the master (SPISCS is low). The slave SPI will drive the
SPIENA signal low when new data is written to the slave shift register
(SPIDAT0) and the slave is selected by the master (SPISCS is low). If the
slave is de-selected by the master (SPISCS goes high), the slave SPIENA
signal is driven low, allowing the master SPI to communicate with other slave
SPIs.
In the master SPI (CLKMOD = 1), the SPISCS pin is configured as a
functional output. If configured as a slave SPI (CLKMOD = 0), the SPISCS
pin is configured as a functional input. A write to the master’s SPIDAT1 shift
register will automatically drive the SPISCS signal low. The master will drive
the SPISCS signal high again after transmitting the new character. If the new
data is written to the master’s SPIDAT0 shift register, the SPISCS signal will
NOT be driven low.
Summary of Contents for TMS470R1 series
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