用PIC32MX250F128D调spi遇到从模式发不出数据的问题
设为主模式时发送正常，设为从模式，另一块单片机模拟外部时钟，不选用片选信号线。往SPI1BUF写数据发现spi发送缓存器一直是满状态！用库函数也不成功，头大呀！
#include <xc.h>

void SPIInit(void)
{
        unsigned int rData;
//        TRISBbits.TRISB14 = 1;
//        PORTBbits.RB14 = 1;
//        RPA0Rbits.RPA0R = 0x03;//master ss
        RPA1Rbits.RPA1R = 0x03;//data out port PA1
        SDI1Rbits.SDI1R = 0x05;//data in port
        SS1Rbits.SS1R = 0x00;//slaver ss
        IEC1CLR = 0x70;
        SPI1CON = 0;//clear
        rData = SPI1BUF;

/*        IFS1CLR = 0x70;
        IPC7CLR = 0x1f000000;
        IPC7SET = 0x04000000;
        IEC1SET = 0x70;*/
//        SPI1BRG = SPI_BRG;  //use for clk
        SPI1STATCLR = 0x40;
//master
//        SPI1CON = 0x8320; //mode 0
//        SPI1CON = 0x8220; //mode1
//        SPI1CON = 0x8360; //mode 2
//        SPI1CON = 0x8260;//mode 3
//slaver       
//        SPI1CON = 0x8100; //mode 0
//        SPI1CON = 0x8000; //mode1
//        SPI1CON = 0x8140; //mode 2
//        SPI1CON = 0x8040;//mode 3
        SPI1CON = 0x8040;
}

unsigned int SPI_SendReadByte(unsigned int dat)
{
        while(SPI1STATbits.SPIBUSY);  
        SPI1BUF = dat;
        while(!SPI1STATbits.SPIRBF);
        return SPI1BUF;
}

void main(void)
{

          //PortInit();
        SPIInit();
        while(OSCCONbits.SLOCK==0);
        while(1)
        {
                SPI_SendReadByte(0xaa);
        }
}