The software reset call is a command sent from the controller on the SPI bus that instructs the SPI target devices that support the command to be reset to the power-up default state.

TXE8116-Q1/TXE8124-Q1 devices use a 24-bit SPI frame for communication. For example, to trigger register reset via software reset command, the controller can configure the SPI frame as the following:

Here is the sample code for this command on the controller side:

// Define the SPI register addresses

#define REGISTER_CMD_BYTE 0x1A // Register command byte of reset register

#define DATA_BITS 0x2 // Set B1 as 1 and B0 as 0 to trigger register reset

#define READ_WRITE_BIT 0 // 0 for Write operation, 1 for Read operation

// Function to send a 24-bit SPI frame to the I/O expander (MSB First)

void SPI_Send(uint32_t data) {

    // Using a hardware SPI peripheral to send the 24-bit data bit by bit (MSB first)

    for (int i = 23; i >= 0; i--) {

    SPI_Transmit((data >> i) & 0x01); // Shift out MSB first

    }

}

// Function to send software reset command to the SPI I/O expander

void SPI_Software_Reset(void) {

    uint32_t frame = 0;

    // Set the Read/Write bit (bit 23)

    frame |= (READ_WRITE_BIT << 23);

    // Set the Register Address (bits 20-16)

    frame |= (REGISTER_CMD_BYTE << 16);

    // Set the Data bits (bits 7-0)

     frame |= (DATA_BITS & 0xFF); // Ensure we only use the lower 8 bits

    // Pull CS low to select the target device

    CS_LOW();

    // Send the constructed SPI frame (MSB first)

    SPI_Send(frame);

    // Pull CS high to deselect the device after transmission

    CS_HIGH();

}