Inputs: byte a[256], bit go
Outputs: byte max_diff, bit done
MAX_DIFF:
  while(1) {
    while(!go);
    done = 0;
    i = 0;
    max = 0;
    min = 255; // largest 8-bit value
    while( i < 256 ) {
      if( a[i] < min ) {
        min = a[i];
      }
      if( a[i] > max ) {
        max = a[i];
      }
      i = i + 1;
    }
    max_diff = max - min;
    done = 1;
  }