求助：C6747如何通过SPI读取ADS8354 转换后输出的48bit的数据？ EDMA3+SPI+ADS8354

参考一下C6748的starterware里的SPI EDMA例程。简单来说，通过CSHOLD可以控制CS。

The chip select signal is held active at the end of a transfer until a control field with new data and
control information is loaded into SPIDAT1. If the new chip select hold information equals the
previous one, the active chip select signal is extended until the end of transfer with CSHOLD
cleared.

/* Assert the CSHOLD line corresponding to the SPI Flash. */
CSHoldAssert();

/* Enable SPI controller to generate DMA events */
SPIIntEnable(SOC_SPI_1_REGS, SPI_DMA_REQUEST_ENA_INT);

/* Wait until both the flags are set to 1 in the callback function. */
while((0 == flagTx) || (0 == flagRx));

flagTx = 0;
flagRx = 0;

/* Deassert the CSHOLD line corresponding to the SPI Flash. */
CSHoldDeassert();

static void CSHoldAssert(void)
{
SPIDat1Config(SOC_SPI_1_REGS, (SPI_CSHOLD | SPI_DATA_FORMAT0), 0x01);
}

/*
** This function deasserts the CSHOLD line.
*/

static void CSHoldDeassert(void)
{
SPIDat1Config(SOC_SPI_1_REGS, SPI_DATA_FORMAT0, 0x01);
}

void SPIDat1Config(unsigned int baseAdd, unsigned int flag, unsigned char cs)
{
unsigned char *ptr = (unsigned char*)(baseAdd + SPI_SPIDAT1);
unsigned char dcs;

*(ptr+3) = (char)((flag >> 24) | (flag & (SPI_SPIDAT1_DFSEL >>
SPI_SPIDAT1_DFSEL_SHIFT)));

dcs = HWREG(baseAdd + SPI_SPIDEF ) & (SPI_SPIDEF_CSDEF);

*(ptr+2) = cs ^ dcs;
}