eeprom.c

PIC单片机的eeprom使用ccs源码

// Written by Ed Waugh 2004, www.edwaugh.co.uk

// for the original source, and hundreds more examples of PIC C code, see:
// http://www.microchipc.com/sourcecode/#eeprom

#use I2C(Master,sda=PIN_C4,scl=PIN_C3,FAST)

void i2c_eeprom_write(unsigned char addrh,unsigned char addrl,unsigned char data);
unsigned char i2c_eeprom_read(unsigned char addrh,unsigned char addrl);
void i2c_eeprom_write_str(unsigned char addrh,unsigned char addrl,char* data);


/************************** Eeprom Write **************************************/
/**** Writes a single byte to the eeprom supports 2^16 addresses ****/

void i2c_eeprom_write(unsigned char addrh,unsigned char addrl,unsigned char data)
{
        i2c_start();
        i2c_write(0xA0);                // send chip addr and set data to write mode
        i2c_write(addrh);               // high addr bits
        i2c_write(addrl);               // low addr bits
        i2c_write(data);                // write data
        i2c_stop();
        delay_ms(5);
}

/************************** Eeprom Read **************************************/
/**** Reads a single byte from the eeprom supports 2^16 addresses ****/

unsigned char i2c_eeprom_read(unsigned char addrh,unsigned char addrl)
{
        unsigned char temp;

        i2c_start();

        i2c_write(0xA0);                // send address data in write mode
        i2c_write(addrh);               // high addr bits
        i2c_write(addrl);               // low addr bits

        i2c_start();
        i2c_write(0xA1);                // change to read mode
        temp = i2c_read(0);             // reads are not acknowledged (0)

        i2c_stop();                     // if no stop() can get continuous read

return temp;
}

/************************** Eeprom write string **************************************/
/**** Writes a null terminated string of any length to the eeprom ****/

void i2c_eeprom_write_str(unsigned char addrh,unsigned char addrl,char* data)
{
        while(*data)
        {
                i2c_start();
                i2c_write(0xA0);                // send chip addr and set data to write mode
                i2c_write(addrh);               // high addr bits
                i2c_write(addrl);               // low addr bits
                i2c_write(*data++);                // write data
                i2c_stop();

                addrl++;
                if(addrl==0x00) addrh++;

                delay_ms(5);
        }
}


/************************** Eeprom read contiguous start **************************************/
/**** starts a contiguous read from the eeprom, use read_contig() after this ****/

int eeprom_read_contig_start(long addr)
{
        int data;
        int upper_addr;
        int lower_addr;

        upper_addr=(int)(addr >> 8);            /*Shift upper address bits to form an int holding just the upper portion of the address*/
        lower_addr=(int)(addr & 0x00FF);        /*Mask off lower address bits and place in int*/

        i2c_start();            /*Start communication */
        i2c_write(0xa0);        /*Xmit control code, chip addr, and write bit */
        i2c_write(upper_addr);  /*X Upper mem addr bits*/
        i2c_write(lower_addr);  /*Lower addr bits*/
        i2c_start();            /*Xmit start again to signify read portion*/
        i2c_write(0xa1);        /*Xmit control code, chip addr, and read bit */
        data=i2c_read();        /*Read data*/

        return(data);
}

/************************** Eeprom read contiguous **************************************/
/**** Reads the next byte of a contiguous read, you must have read the 1st byte with contig_start ****/

int eeprom_read_contig(void)
{
        int data;

        data=i2c_read();        /*Read data*/

        return(data);
}

/************************** Eeprom end read contiguous **************************************/
/**** ends contiguous read ****/

int eeprom_read_contig_stop(void)
{
        int data;

        data=i2c_read(0);       /*Read data - no ack*/
        i2c_stop();             /*Stop communication*/

        return(data);
}