Spi 3-Wire Slave Mode; 3-Wire Spi Pin Configuration - Texas Instruments Concerto F28M35 Series Technical Reference Manual

Table of Contents

indicates how data is received or transmitted in the various SPI modes while the TALK bit is

set or cleared.

SPI 3-Wire Mode Code Examples

In addition to the normal SPI initialization, to configure the SPI module for 3-wire mode, the TRIWIRE bit

(SPIPRI.0) must be set to 1. After initialization, there are several considerations to take into account when

transmitting and receiving data in 3-wire master and slave mode. The following examples demonstrate

these considerations.

In 3-wire master mode, SPICLKx, SPISTEx, and SPISIMOx pins must be configured as SPI pins

(SPISOMIx pin can be configured as non-SPI pin). When the master transmits, it receives the data it

transmits (because SPISIMOx and SPISOMIx are connected internally in 3-wire mode). Therefore, the

junk data received must be cleared from the receive buffer every time data is transmitted.

Example 12-4. 3-Wire Master Mode Transmit

Uint16 data;

Uint16 dummy;

SpiaRegs.SPICTL.bit.TALK = 1;

SpiaRegs.SPITXBUF = data; // Master transmits data

while(SpiaRegs.SPISTS.bit.INT_FLAG !=1) {} // Waits until data rx'd

dummy = SpiaRegs.SPIRXBUF;

SPRUH22I – April 2012 – Revised November 2019

Submit Documentation Feedback

Figure 12-9. SPI 3-wire Slave Mode

Table 12-6. 3-Wire SPI Pin Configuration

SPIPRI[TRIWIRE]

SPICTL[TALK]

Disconnect from SPI

// Enable Transmit path

// Clears junk data from itself

// bc it rx'd same data tx'd

C28 Serial Peripheral Interface (SPI)

Enhanced SPI Module Overview

Disconnect from SPI

Chapters

Table of Contents