extMem.c

#include <reg52.h>

sbit errorLed = P1 ^ 0;
sbit initLed = P1 ^ 7;
sbit flashLed = P1 ^ 1;

bit errorSignal = 0x20 ^ 0;

unsigned char xdata initLoc _at_ 0x0000;
unsigned char xdata codeLoc _at_ 0x8000;
unsigned char xdata *ptr;

void delay();
void flash();
void populate();
void error();

void main()
{
  errorSignal = 0;
  errorLed = 1;
  initLed = 1;
  flashLed = 1;

  int i;

  for (i = 5; i > 0; i--)
  {
    flash();
  }

  populate();

  while (1)
  {
    if (errorSignal)
    {
      break;
    }
    else
    {
      flash();
    }
  }
}

void delay()
{
  unsigned char i, j, k;
  for (i = 3; i > 0; i--)
    for (j = 255; j > 0; j--)
      for (k = 255; k > 0; k--)
        ;
}

void flash()
{
  flashLed = flashLed ^ 0x1;
  delay();
}

void error()
{
  initLed = 1;
  errorLed = 0;
  errorSignal = 1;
}

void populate()
{
  ptr = &initLoc;

  *ptr = 0x02;
  ptr++;
  *ptr = 0x08;
  ptr++;
  *ptr = 0x0c;
  ptr++;

  ptr = &codeLoc;

  *ptr = 0xc2;
  ptr++;
  *ptr = 0x91;
  ptr++;
  *ptr = 0x12;
  ptr++;
  *ptr = 0x08;
  ptr++;
  *ptr = 0x18;
  ptr++;
  *ptr = 0xd2;
  ptr++;
  *ptr = 0x91;
  ptr++;
  *ptr = 0x12;
  ptr++;
  *ptr = 0x08;
  ptr++;
  *ptr = 0x18;
  ptr++;
  *ptr = 0x80;
  ptr++;
  *ptr = 0xf4;
  ptr++;
  *ptr = 0x78;
  ptr++;
  *ptr = 0x7f;
  ptr++;
  *ptr = 0xe4;
  ptr++;
  *ptr = 0xf6;
  ptr++;
  *ptr = 0xd8;
  ptr++;
  *ptr = 0xfd;
  ptr++;
  *ptr = 0x75;
  ptr++;
  *ptr = 0x81;
  ptr++;
  *ptr = 0x08;
  ptr++;
  *ptr = 0x02;
  ptr++;
  *ptr = 0x08;
  ptr++;
  *ptr = 0x00;
  ptr++;
  *ptr = 0x7f;
  ptr++;
  *ptr = 0xff;
  ptr++;
  *ptr = 0x7e;
  ptr++;
  *ptr = 0xff;
  ptr++;
  *ptr = 0xde;
  ptr++;
  *ptr = 0xfe;
  ptr++;
  *ptr = 0xdf;
  ptr++;
  *ptr = 0xfa;
  ptr++;
  *ptr = 0x22;
  ptr++;
}