我想写个C51与FPGA的SPI接口的C程序，我知道51要用模拟的SPI，哪位大贤能帮帮忙，让我学习一下。

这是 读写pcf2127a的程序。用spi接口。

cpu 是51兼容系列 cy7c68013

#define spi_read 0x20

#define spi_write 0xa0

void spi_start(void)

{ OEE|=spi_ce+spi_di+spi_clk;

OEE &= ~spi_do;

SYNCDELAY;

IOE&=~(spi_ce|spi_clk);

SYNCDELAY;

}

void spi_stop(void)

{

IOE |=spi_ce;

SYNCDELAY;

}

void spi_wr(unsigned char command)

{

char i;

for (i=0;i<8;i++)

{

if((command&0x80)==0x80) {IOE |=spi_di;}else {IOE &=~spi_di;}

command<<=1;

SYNCDELAY;

IOE |=spi_clk;

SYNCDELAY;

IOE &=~spi_clk;

SYNCDELAY;

SYNCDELAY;

}

}

unsigned char spi_rd(void)

{

unsigned char bret;

char i;

bret=0;

for (i=0;i<8;i++)

{IOE |=spi_clk;

bret<<=1;

SYNCDELAY;

SYNCDELAY;

if((IOE&spi_do)==spi_do){ bret++;}

IOE &= ~spi_clk;

SYNCDELAY;

SYNCDELAY;

}

return bret;

}

void spi_writedata(unsigned char address,unsigned char command)

{

address&=0x1f;

address|=0x20;

spi_start();

spi_wr(address);

SYNCDELAY;

spi_wr(command);

spi_stop();

}

unsigned char spi_readdata(unsigned char address)

{unsigned char bret;

address&=0x1f;

address |=0xa0;

spi_start();

spi_wr(address);

SYNCDELAY;

bret=spi_rd();

spi_stop();

return bret;

}

void read_time(unsigned char address)

{spi_start();

spi_wr(address|0xa0);

EP0BUF[8] =spi_rd();//秒

EP0BUF[9]= spi_rd();//分

EP0BUF[10]= spi_rd();//时

EP0BUF[11]= spi_rd();//日

EP0BUF[12]= spi_rd();

hEP0BUF[13]= spi_rd();//月

EP0BUF[14]= spi_rd();//年

spi_stop();

}

void write_ram(unsigned int address,unsigned int command)

{unsigned char addh,addl,commandh,commandl;

addh=(address&0xff00)>>8;

addl=address&0x00ff;

commandh=(command&0xff00)>>8;

commandl=command&0x00ff;

spi_writedata(0x1a,addh);

spi_writedata(0x1b,addl);

spi_writedata(0x1c,commandh);

spi_writedata(0x1c,commandl);

}

unsigned int read_ram(unsigned int address)

{

unsigned char addh,addl,commandh,commandl;

unsigned int command;

addh=(address&0xff00)>>8;

addl=address&0x00ff;

spi_writedata(0x1a,addh);

spi_writedata(0x1b,addl);

commandl=spi_readdata(0x1d);

commandh=spi_readdata(0x1d);

command=(commandh<<8)+commandl;

return command;

}

SPI协议中接收和发送数据是一体的,数据传输的线路为一个循环链路(loop)如果主机发送数据给从机,则必须从从机读取数据(即从机也发送数据到主机)同理,如果主机读取从机发来的数据,也必须同时发送数据给从机总之,同一个时钟周期内,读和写2个 *** 作都必须执行

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