[Moved] problem in saving data to eeprom

[adnansarwar2050]

i am using 24c02 eeprom for the first time. i have coded for writing and reading data but the data i am reading is not matching with that i have written. Please check my code where is the mistake. i am using 89c51.

#include <AT89x51.h>
#include<intrins.h>
sbit sda = P1^0;
sbit clk = P1^1;
int i;


void EEPROM_Write(char address,char dat)
	{
		char device = 0xA0;
		sda = 1;
		clk = 1;
		_nop_();
		sda = 0;
		clk = 0;

		for (i = 0; i<8; i++)
			{
				clk = 0;
				if(device & 0x80)
					sda = 1;
				else
					sda = 0;
				clk = 1;
				device = device << 1;
			}

		 clk = 0;
		 _nop_();
		 clk = 1;
		 _nop_();

		 if(!sda)
		 {
		 	clk = 0;
			_nop_();
			clk = 1;
			_nop_();
			clk = 0;


			for (i = 0; i<8; i++)
			{
				clk = 0;
				if(address & 0x80)
					sda = 1;
				else
					sda = 0;
				clk = 1;
				address = address << 1;
			}

			if(!sda)
		 		{
		 			clk = 0;
					_nop_();
					clk = 1;
					_nop_();
					clk = 0;
					P2 = 0x29;

					for (i = 0; i<8; i++)
						{
							clk = 0;
							if(dat & 0x80)
								sda = 1;
							else
								sda = 0;
							clk = 1;
							dat = dat << 1;
						}

					 	if(!sda)
					 		{
					 			clk = 0;
								_nop_();
								clk = 1;
								_nop_();
								clk = 0;
							}

						sda = 0;
						_nop_();	
						clk = 1;
						sda = 1;
						_nop_();
						clk = 0;
						_nop_();
						_nop_();
						_nop_();
						_nop_();


				}
		 }
	
	}




char EEPROM_Read(char address)
	{
		char device = 0xA1;
		char readvalue;
		sda = 1;
		clk = 1;
		_nop_();
		sda = 0;
		clk = 0;

		for (i = 0; i<8; i++)
			{
				clk = 0;
				if(device & 0x80)
					sda = 1;
				else
					sda = 0;
				clk = 1;
				device = device << 1;
			}

		 clk = 0;
		 _nop_();
		 clk = 1;
		 _nop_();

		 if(!sda)
		 {
		 	clk = 0;
			_nop_();
			clk = 1;
			_nop_();
			clk = 0;


			for (i = 0; i<8; i++)
			{
				clk = 0;
				if(address & 0x80)
					sda = 1;
				else
					sda = 0;
				clk = 1;
				address = address << 1;
			}

			if(!sda)
		 		{
		 			clk = 0;
					_nop_();
					clk = 1;
					_nop_();
					clk = 0;
					
					

					for (i = 0; i<8; i++)
						{	
							clk=1;
							_nop_();
							if(sda == 1)
								readvalue++;
							clk=0;
							readvalue = readvalue<<1;
						}

					 	if(!sda)
					 		{
					 			clk = 0;
								_nop_();
								clk = 1;
								_nop_();
								clk = 0;
							}
					
						sda = 0;
						_nop_();	
						clk = 1;
						sda = 1;
						_nop_();
						clk = 0;
				}
		 }

		 return (readvalue);
	}





void main ()
	{
		char address = 0x05;
		char dat = 0x68;
		char read;
		P0 = 0;
		P1 = 0;
		P2 = 0;
		P3 = 0;
		
		EEPROM_Write(address,dat);
		read = EEPROM_Read(address);

		if (read == dat)
			P1_5 = 1;
		while (1)
			{
				
			}

	}

 

[james.smith]

Re: problem in saving data to eeprom

Hey, I realise that this post is almost two years old but maybe if there's still someone looking for an answer.

If you look at the datasheet of that EEPROM,
http://www.atmel.com/Images/doc0180.pdf
on p. 5 it describes a write cycle time. After you write to it you need to leave it alone for 5 ms at least before you try to read, otherwise the operation doesn't happen correctly.

Regards,
James