Arduino chip as Stepper Controller

Using Arduino Motors, Mechanics, Power and CNC
2

Got to thinking about this and came up with some code to test -
Posting it here to see what someone else might think.

/*
Step & Direction Stepper Driver
 Pins 9, 10, 11, 12 are tied to transistors 
 for each of the motor phases.
 Pins 2 & 3 are used as interrupts,
 Pin 2 as Step and 3 as Direction.
 */

int pin1 =9;
int pin2 = 10;
int pin3 = 11;
int pin4 = 12;
int pinDir = 3;
volatile int ctr;
volatile int dir;

void setup()
{
  pinMode(pin1, OUTPUT);
  pinMode(pin2, OUTPUT);
  pinMode(pin3, OUTPUT);
  pinMode(pin4, OUTPUT);
  pinMode(pinDir, INPUT);
  ctr=0;
  dir = 0;
  attachInterrupt(0, Step, RISING);
  attachInterrupt(1, Direction, CHANGE);

}

void loop()
{
}

void Step()
{
  if (dir) 
  {
    ctr++ & 3;
  }
  else 
  {
    ctr-- & 3;
  }

  switch (ctr){
  case 0:
    digitalWrite(pin1,HIGH);
    digitalWrite(pin2,LOW);
    digitalWrite(pin3,LOW);
    digitalWrite(pin4,LOW);
    break;
  case 1:
    digitalWrite(pin1,LOW);
    digitalWrite(pin2,HIGH);
    digitalWrite(pin3,LOW);
    digitalWrite(pin4,LOW);
    break;
  case 2:
    digitalWrite(pin1,LOW);
    digitalWrite(pin2,LOW);
    digitalWrite(pin3,HIGH);
    digitalWrite(pin4,LOW);
    break;
  case 3:
    digitalWrite(pin1,LOW);
    digitalWrite(pin2,LOW);
    digitalWrite(pin3,LOW);
    digitalWrite(pin4,HIGH);
    break;
  }   
}  
void Direction()
{
  if ( digitalRead(pinDir) )
  {
    dir = 0;
  }
  else
  {
    dir=-1;
  }  
}