PWM by pic 16F877A

Hey guys,

I am using 16F877A to output PWM, increasing and decreasing it via two push buttons its based on the code used in DC Motor Speed Control using PWM with PIC Microcontroller in MikroC but the problem is that after a certain PWM value the PWM  will not decrease and I have also added a switch with instantly makes duty value zero but it also doesn’t work after a certain pwm value and I have tried it on Proteus as well as with leds in real life but they give the same result. Only way it goes low is to keep pressing the UP button then some how it come down to a low value then other two switches start working and I then can switch it pwm off. Don’t know whats wrong.

Here is the code:-

{
  adc = ADC_Read(1); // Get 10-bit results of AD conversion
  rpm_temp = adc * 2; //converting analog value to rpm
  WordToStr(rpm_temp, speed_out); //converting integer to string to disply on LCD
  Lcd_Out(2,9,speed_out);//Write speed in 2st row 6th col
  Delay_ms(100);
  if (RD0_bit ==0 && duty<250) //if button on RD0 pressed
  {
    Delay_ms(100);
    duty = duty + 10;  //increment current_duty
    PWM1_Set_Duty(duty);  //Change the duty cycle
  }
  if (RD1_bit ==0 && duty >0) //button on RD1 pressed
  {
    Delay_ms(100);
    duty = duty - 10;  //decrement duty
    PWM1_Set_Duty(duty);
  }
  if (RD2_bit ==0 && duty >0) //button on RD2 pressed
  {
    Delay_ms(100);
    duty = 0;  //reset duty
    PWM1_Set_Duty(duty);
  }