#include <reg51.h>
sbit MTR = P1^0
void MSDelay(unsigned int value)
void main()
  {
  unsigned char z
  P2 = 0xFF
  z = P2
  z = z & 0x03
  MTR = 0
  while(1)
    {
     switch(z)
       {
       case(0):
         {
           MTR = 1
           MSDelay(25)
           MTR = 0
           MSDelay(75)
           break
         }
       case(1):
         {
           MTR = 1
           MSDelay(50)
           MTR = 0
           MSDelay(50)
           break
         }
       case(2):
         {
           MTR = 1
           MSDelay(75)
           MTR = 0
           MSDelay(25)
           break
         }
       default:
         MTR = 1
    }
  }