Spi 3-Wire Mode Description; Spi 3-Wire Master Mode; 4-Wire Vs. 3-Wire Spi Pin Functions - Texas Instruments Concerto F28M35 Series Technical Reference Manual

Table of Contents

Advertisement

Enhanced SPI Module Overview
SPI FIFO mode

12.1.7 SPI 3-Wire Mode Description

SPI 3-wire mode allows for SPI communication over 3 pins instead of the normal 4 pins.
In master mode, if the TRIWIRE (SPIPRI.0) bit is set, enabling 3-wire SPI mode, SPISIMOx becomes the
bi-directional SPIMOMIx (SPI master out, master in) pin, and SPISOMIx is no longer used by the SPI. In
slave mode, if the TRIWIRE bit is set, SPISOMIx becomes the bi-directional SPISISOx (SPI slave in, slave
out) pin, and SPISIMOx is no longer used by the SPI.
The table below indicates the pin function differences between 3-wire and 4-wire SPI mode for a master
and slave SPI.
4-wire SPI
SPICLKx
SPISTEx
SPISIMOx
SPISOMIx
Because in 3-wire mode, the receive and transmit paths within the SPI are connected, any data
transmitted by the SPI module is also received by itself. The application software must take care to
perform a dummy read to clear the SPI data register of the additional received data.
The TALK bit (SPICTL.1) plays an important role in 3-wire SPI mode. The bit must be set to transmit data
and cleared prior to reading data. In master mode, in order to initiate a read, the application software must
write dummy data to the SPI data register (SPIDAT or SPIRXBUF) while the TALK bit is cleared (no data
is transmitted out the SPIMOMI pin) before reading from the data register.
SPI Module
958
C28 Serial Peripheral Interface (SPI)
Table 12-4. SPI Interrupt Flag Modes (continued)
SPI Interrupt
Interrupt
FIFO receive
RXFFIL
Transmit empty
TXFFIL
Table 12-5. 4-wire vs. 3-wire SPI Pin Functions
3-wire SPI (Master)
SPICLKx
SPISTEx
SPIMOMIx
Free
Figure 12-8. SPI 3-wire Master Mode
Data RX
SPIDAT
Data TX
Talk
SPICTL.1
Copyright © 2012–2019, Texas Instruments Incorporated
Interrupt
FIFO Enable
RXFFIENA
TXFFIENA
3-wire SPI(Slave)
SPICLKx
SPISTEx
Free
SPISISOx
GPIO MUX
Free pin
SPIMOMIx
SPRUH22I – April 2012 – Revised November 2019
www.ti.com
(1)
Interrupt
1
SPIRXINT
1
SPITXINT
Submit Documentation Feedback

Advertisement

Table of Contents
loading

Table of Contents