Hi all

I am using the 16F684 to control a stepper motor in an application where it needs to remember it's position and direction when the power is turned off.  This information is read on power-on, and if it is not valid data, the operator is signaled to manually reset the mechanism to 0.  I am having a terrible time trying to get the eeprom code to work and would really appreciate some help.  The project is for one of my kids, who is making an unusual electro-mechanical device.  Thanks in advanced.

Here is my code;


#include <system.h>
#include <boostc.h>
#pragma DATA 0x2007, _WDT_OFF & _BOD_OFF & _INTOSCIO & _PWRTE_OFF & _MCLRE_OFF
#pragma CLOCK_FREQ 4000000


#define x_error porta.2

unsigned char count;                                    //for tracking rolling count in the interrupt routine
unsigned char data_ok, auto_cw;                  //character for storing position data_ok flag and direction
int max_position, cur_position;                      //16 bit integers for tracking position
unsigned char position_high, position_low;     //for storing high and low bytes of cur_position


void write(char data, char address);
char read(char address);

void main(void)
{


//initialize PIC
  
//read variables stored previously


 auto_cw = read(0);                           //retrieve position, count, direction and data_ok flag
 position_low = read(1);
 position_high = read(2);
 count = read(4);
 data_ok = read(3);                          //data_ok is a flag to detect if power was interrupted
                                                      //during normal power down, a specific value is stored
 cur_position = position_high<<8;     //reconstruct 16 bit cur_position from 8 bit words
 cur_position |= position_low;

 if(data_ok!=0xF0)                          //check flag & if data is not valid, then 
  {
  x_error = 1;                                 //flag operator - turn on fault led
  cur_position=0;                           //reset variables
  auto_cw=1;  
  x_error = 0;                                //turn off fault led
  }
 
 pie1 = 0;                                    //disable interrupt during eeprom write
 data_ok=0;                                //store 0 in data_ok so that if power is interupted,
 write(data_ok,3);                        //it will be detected on power up.
 pie1 = 0b00000001;                   //enable timer1 overflow interrupt


 
 while(1)   //main loop
 {


//do the main loop motor control, until operator initiates power off sequence

 if (test_bit(porta,0))                   //test for pwr_off 
  {
  intcon = 0b00000000;                          //disable interrupts during eeprom write
                                                           //store count, auto_cw and cur_position
  data_ok = 0xF0;                                 //store data_ok flag to indicate valid position
  position_low = cur_position & 0x00FF;
  position_high = cur_position>>8;
  write(auto_cw, 0);                               //write position and direction data, and data_ok  flag
  write(position_low,1);
  write(position_high,2);
  write(count,4);
  write(data_ok,3);
  while (test_bit(porta,0));                     //then wait here until power goes off, or pwr_off input changes
  intcon = 0b11000000;                       //if power goes back on, enable interrupts
    }
 }
}



void write(char data, char address)     //writes 8 bit data to address in eeprom
 {
 eedata = data;
 eeadr = address;
 eecon1 = 0b00000100;
 eecon2 = 0x55;
 eecon2 = 0xAA;
 eecon1 = 0b00000110;
 while(test_bit(eecon1,1));                 //wait for write to complete
 eecon1 = 0;
 pir1 =0;                                          //clear interrupt flages - PIR1<7>
 }

char read(char address)                     //reads 8 bit data from address in eeprom
 {
 eeadr = address;
 eecon1 = 0b00000001;
 pir1 = 0;
 return eedata;
 }
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