gpio模拟以太网SMI接口，读寄存器有问题

因为F407不支持op code的设置，所以采用gpio模拟smi接口操作，但是读出来的数据有问题，全是0xffff，找不出问题，是delay_us(1)延时太长吗？
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//IO方向#define MDIO_IN()  {GPIOA->MODER&=~(3<<(2*2));GPIOA->MODER|=0<<2*2;}//PA2#define MDIO_OUT() {GPIOA->MODER&=~(3<<(2*2));GPIOA->MODER|=1<<2*2;} //PA2#define MDIO    PAout(2) //SCL#define MDC     PCout(1) //SDA #define READ_MDIO  PCin(1) //SDAvoid SMI_Init(void) {//配置PA2 PC1为推完输出，GPIO模拟SMIGPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;//推完输出GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP ;//GPIO_PuPd_UP GPIO_PuPd_NOPULLGPIO_Init(GPIOA, &GPIO_InitStructure);//PA2 MDIO    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL ;//GPIO_PuPd_UP GPIO_PuPd_NOPULLGPIO_Init(GPIOC, &GPIO_InitStructure);//PC1 MDC ，不需要上拉    MDIO = 1;    MDC = 0;}u8 SMI_Read_One_Byte(void){    u8 i, receive=0;//    MDIO_IN();    for(i = 0; i < 8; i++)    {receive<<=1;        MDC=0;//拉低时钟delay_us(1);MDC=1;  //上升沿传输数据delay_us(1);if(READ_MDIO) receive|= 0x01; //上升沿，高电平期间读数据MDC=0;//时钟恢复低电平    }    return receive;}u8 SMI_Read_2Bit(void){    u8 i, receive=0;//    MDIO_IN();    for(i = 0; i < 2; i++)    {        receive<<=1;        MDC=0;//拉低时钟delay_us(1);MDC=1;  //上升沿传输数据delay_us(1);        if(READ_MDIO) receive|= 0x01; //上升沿，高电平期间读数据        MDC=0;//恢复低电平    }    return receive;}void SMI_Write_One_Byte(u8 data){    u8 i;//    MDIO_OUT();    for(i = 0; i < 8; i++)    {        MDC=0;        MDIO=(data&0x80)>>7;//准备数据        delay_us(1);        MDC=1;  //上升沿传输数据        delay_us(1); //保持一段时间        MDC = 0;//恢复低电平        data<<=1;    }}void SMI_Write_2Bit(u8 data){    u8 i;    MDIO_OUT();    for(i = 0; i < 2; i++)    {        MDC=0;        MDIO=(data&0x2)>>1;        delay_us(1);        MDC=1;      //上升沿传输数据        delay_us(1); //保持一段时间        MDC = 0;//恢复低电平        data<<=1;    }}#define START_OF_FRAME_2bit 0x01#define READ_OP_CODE_2bit 0x2#define WRITE_OP_CODE_2bit 0x1#define SMI_OP_CODE_2bit 0x00#define SMI_TA 0x02void SMI_Write_Frame(u16 PHYAddress, u16 PHYReg, u16 PHYValue){    u8 addr;        addr = (PHYAddress & 0x7) <<5 | (PHYReg & 0x1F);    MDIO_OUT();      ////32 bit Preamble    SMI_Write_One_Byte(0xFF);    SMI_Write_One_Byte(0xFF);    SMI_Write_One_Byte(0xFF);    SMI_Write_One_Byte(0xFF);    SMI_Write_One_Byte(0xFF);    SMI_Write_One_Byte(0xFF);    SMI_Write_One_Byte(0xFF);    SMI_Write_One_Byte(0xFF);    SMI_Write_2Bit(START_OF_FRAME_2bit);    SMI_Write_2Bit(WRITE_OP_CODE_2bit);    SMI_Write_2Bit(0x00);       //dir: 0x0 is write    SMI_Write_One_Byte(addr);    SMI_Write_2Bit(SMI_TA);    SMI_Write_One_Byte(0xFF);    SMI_Write_One_Byte(PHYValue);    MDIO_IN();//恢复输入高阻态}u16 SMI_Read_Reg(u16 PHYAddress, u16 PHYReg){    u8 addr;    u16 data;        addr = (PHYAddress & 0x7)<<5 | (PHYReg & 0x1F);       ////32 bit Preamble    MDIO_OUT();    SMI_Write_One_Byte(0xFF);    SMI_Write_One_Byte(0xFF);    SMI_Write_One_Byte(0xFF);    SMI_Write_One_Byte(0xFF);    SMI_Write_2Bit(START_OF_FRAME_2bit);    SMI_Write_2Bit(READ_OP_CODE_2bit);    SMI_Write_2Bit(0x0);       //PHYAD[4:3] decide dir: 0x2/0x3 is write    SMI_Write_One_Byte(addr);        MDIO_IN();    data = SMI_Read_2Bit();//SMI_TA should be Z0    data = SMI_Read_One_Byte();    data = data << 8;    data = data | SMI_Read_One_Byte();    return data;}u8 KSZ8863_Get_Reg_Value(u8 port, u8 reg_num){u16 reg;//reg = ETH_ReadPHYRegister(port, reg_num); //从port1的1号寄存器中读取网络速度和双工模式reg = SMI_Read_Reg(port, reg_num);printf("port %d, reg 0x%x = 0x%x rn", port, reg_num, reg);return reg;}void KSZ8863_Print_Reg_Value(void){u8 i, port;for(port = 1; port < 4; port++){for(i = 0; i < 6; i++){KSZ8863_Get_Reg_Value(port, i);delay_ms(100);}}}