Master
Slave
(Master = 1; CLKMOD = 1)
(Master = 0; CLKMOD = 0)
SPIDAT1
SPIDAT0
MSB
LSB
MSB
LSB
Write to SPIDAT1
SPISOMI
SPISIMO
SPISOMI
SPISIMO
SPICLK
SPICLK
SPICS
SPICS
Write to SPIDAT0
Write to SPIDAT0 (SLAVE)
Write to SPIDAT1 (MASTER)
SPISIMO
SPISOMI
SPIENA
SPIENA
SPIENA
SPICS
SPICLK
Operating Modes
1125
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Multi-Buffered Serial Peripheral Interface Module (MibSPI) with Parallel Pin
Option (MibSPIP)
24.2.5 Five-Pin Operation (Hardware Handshaking)
Five-pin operation combines the functionality of three-pin mode, plus the enable pin and one or more chip
select pins. The result is full hardware handshaking. To use this mode, both the SPIENA pin and the
required number of SPICS pins must be configured as functional pins.
If the SPIENA pin is in high-impedance mode (ENABLE_HIGHZ = 1), the slave SPI will put this signal into
the high-impedance state by default. The slave will drive the signal SPIENA low when new data is written
to the slave shift register and the slave has been selected by the master (SPICS is low).
If the SPIENA pin is in push-pull mode (ENABLE_HIGHZ = 0), the slave SPI drives this pin high by default
when it is in functional mode. The slave SPI will drive the SPIENA signal low when new data is written to
the slave shift register (SPIDAT0/SPIDAT1) and the slave is selected by the master (SPICS is low). If the
slave is deselected by the master (SPICS goes high), the slave SPIENA signal is driven high.
NOTE:
Push-pull mode of the SPIENA pin can be used only when there is a single slave in the
system. When multiple SPI slave devices are connected to the common SPIENA pin, all of
the slaves should configure their SPIENA pins in high-impedance mode.
In master mode, if the SPICS pins are configured as functional pins, then the pins will be in output mode.
A write to the master’s SPIDAT1/SPIDAT0 register will automatically drive the SPICS signals low. The
master will drive the SPICS signals high again after completing the transfer of the bits of the data.
In slave mode (CLKMOD = 0), the SPICS pins act as SPI functional inputs.
Figure 24-5. SPI Five-Pin Option with SPIENA and SPICS