c51的SD卡源代码

SD卡接口程序/************************************************************/ /* SD Code for M32L */ /* By pasyong */ /* 2006-4 */ /* Base ICC6.31A */ /************************************************************/ #include <iom32v.h> #include <macros.h> #include "1011.h" #define uchar unsigned char #define uint unsigned int #define MMC_CS_PIN BIT(4) //PORTB.4 #define MMC_PORT PORTB uchar reading=0,a=0,pointer=0; void sd_port_init() { MMC_PORT|=MMC_CS_PIN; } uchar BUFFER[512]; //扇区缓冲区 uint i=0; void delay_nus(uint n) { unsigned char b; for (b = 1; b<n; b++) ; } //**************************************************************************** //Send a Command to MMC/SD-Card //Return: the second byte of response register of MMC/SD-Card //**************************************************************************** uchar SD_Write_Command(uchar cmd,unsigned long arg) { uchar tmp; uchar retry=0; //MMC_PORT|=MMC_CS_PIN; //SD卡关闭 //send 8 Clock Impulse Write_Byte_SPI(0xFF); //set MMC_Chip_Select to low (MMC/SD-Card active) MMC_PORT&=~MMC_CS_PIN; //SD卡使能 Write_Byte_SPI(cmd|0x40); //送头命令 Write_Byte_SPI(arg>>24); Write_Byte_SPI(arg>>16); //send 6 Byte Command to MMC/SD-Card Write_Byte_SPI(arg>>8); Write_Byte_SPI(arg&0xff); Write_Byte_SPI(0x95); //仅仅对RESET有效的CRC效验码 //get 8 bit response //Read_Byte_MMC(); //read the first byte,ignore it. do { //Only last 8 bit is used here.Read it out. tmp = Read_Byte_SPI(); retry++; } while((tmp==0xff)&&(retry<100)); //当没有收到有效的命令的时候 if(reading==0) MMC_PORT|=MMC_CS_PIN; //MMC_CS_PIN=1; else MMC_PORT&=~MMC_CS_PIN; //MMC_CS_PIN=0; return(tmp); } //**************************************************************************** //SD卡初始化(SPI-MODE) //**************************************************************************** uchar SD_Init(void) { uchar retry,temp; uchar i; MMC_PORT&=~MMC_CS_PIN; //SD卡使能 delay_nus(250); //Wait MMC/SD ready... for (i=0;i<0x0f;i++) { Write_Byte_SPI(0xff); //send 74 clock at least!!! } //Send Command CMD0 to MMC/SD Card retry=0; do { //retry 200 times to send CMD0 command temp=SD_Write_Command(0,0); retry++; if(retry==100) { ;//CMD0 Error! } } while(temp!=1); //Send Command CMD1 to MMC/SD-Card retry=0; do { //retry 100 times to send CMD1 command temp=SD_Write_Command(1,0); retry++; if(retry==100) { ; } } while(temp!=0); retry=0; SD_Write_Command(16,512); //设置一次读写BLOCK的长度为512个字节 MMC_PORT|=MMC_CS_PIN; //MMC_CS_PIN=1; //set MMC_Chip_Select to high return(0); //All commands have been taken. } //**************************************************************************** //从SD卡读一个扇区 Return 0 if no Error. //**************************************************************************** uchar SD_Read_Block(unsigned long address) { uchar temp=0;uint i=0; reading=1; temp=SD_Write_Command(17,address); //读出RESPONSE while (Read_Byte_SPI()!= 0xfe) {;} //直到读取到了数据的开始头0XFE，才继续 for(i=0; i<512; i++) { BUFFER[i]=Read_Byte_SPI(); } Read_Byte_SPI();//CRC - Byte Read_Byte_SPI();//CRC - Byte reading=0; MMC_PORT|=MMC_CS_PIN; //关闭SD卡 return(temp); }