Architecture
1425
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Serial Peripheral Interface (SPI)
29.2.10 SPI Operation: 5-Pin Mode
The 5-pin mode is a superset of both 4-pin modes. To use the 5-pin mode, both the SPIx_ENA and the
SPIx_SCS[n] pins must be configured as functional pins, in addition to the SPIx_CLK, SPIx_SIMO, and
SPIx_SOMI pins by configuring the SPI pin control register 0 (SPIPC0).
shows the SPI 5-pin
option.
In SPI master mode, the SPIx_SOMI and SPIx_ENA pin output buffer is in a high-impedance state and
the SPIx_CLK, SPIx_SIMO, and SPIx_SCS[n] pin output buffer is enabled. In SPI slave mode, the
SPIx_CLK, SPIx_SIMO, and SPIx_SCS[n] pin output buffer is in a high-impedance state, and the
SPIx_SOMI pin output buffer is enabled and disabled asynchronously by the SPIx_SCS[n] input and the
SPIx_ENA pin output buffer enable depends upon the status of the transmit buffer and the state of the
SPIx_SCS[n] input. In SPI slave mode, the assertion of the SPIx_ENA pin by the slave is delayed until the
master asserts SPIx_SCS[n], thereby, allowing multiple SPI slaves on a single SPI bus, each slave with its
own enable pin.
If the SPIx_ENA pin is in high-impedance mode (ENABLEHIGHZ = 1 in the SPI interrupt register
(SPIINT0)), the slave SPI will put this signal into the high-impedance state by default. The slave SPI will
drive the SPIx_ENA signal low when new data is written to the slave transmit shift register and the slave
has been selected by the master (SPIx_SCS[n] is low).
If the SPIx_ENA pin is in push-pull mode (ENABLEHIGHZ = 0), the slave SPI will drive this pin high by
default when it is in functional mode. The slave SPI will drive the SPIx_ENA signal low when new data is
written to the slave transmit shift register and the slave is selected by the master (SPIx_SCS[n] is low). If
the slave is deselected by the master (SPIx_SCS[n] goes high), the slave SPIx_ENA signal is driven high
automatically.
NOTE:
Either SPIDAT0 or SPIDAT1 can be used on both master and slaves sides.