hardware_delay_50ms.c

CODE for embedded C ,hand coding version

/*--------------------------------------------------------------*-
  Hardware_Delay_50ms.C(v1.00)
  Author:06_Digital_Media
  All Right Reserved
  ----------------------------------------------------------------
  A test programe for hardware-based delays
  -*--------------------------------------------------------------*/

  #include <reg52.h>
  sbit LED_pin = P1^5 ;
  bit LED_state_G ;

  void LED_FLASH_Init(void);
  void LED_FLASH_Change_State(void);

  void DELAY_HARDWARE_One_Second(void);
  void DELAY_HARDWARE_50ms(void);

  /*------------------------------------------------------------*/
  void main(void){
   LED_FLASH_Init();

   while(1){
    //Change the LED state (OFF to ON ,or vice versa)
	LED_FLASH_Change_State();

	//Delay for approx 1000 ms

	DELAY_HARDWARE_One_Second();

   }
  }

  /*------------------------------------------------------------*-
   LED_FLASH_Init()
   Prepare for LED_Change_State() function - see below

   -*------------------------------------------------------------*/
   void LED_FLASH_Init(void){
    LED_state_G = 0;
   }


   /*-------------------------------------------------------------*-
   LED_FLASH_Change_State()
   Change the state of an LED (or pulses a buzzer ,etc) on a specified port pin

   Must call at twice the required flash rate :thus  for 1HZ flash (on for 0.5 seconds,
   off for 0.5 seconds ) must call every 0.5 seconds
   -*---------------------------------------------------------------*/

   void LED_FLASH_Change_State(void){
    
    //Change the LED from  OFF to ON ( or vice versa)

   if(LED_state_G ==1){
     LED_state_G = 0 ;
	 LED_pin = 0 ;
   }else{
     LED_state_G = 1;
	 LED_pin =1 ;
   }
   }

   /*----------------------------------------------------------*-
    DELAY_HARDWARE_One_Second()
	Hardware delay of 1000 ms
    ***Assumes 12mHZ 8051 (12 osc cycles) ***
	-*----------------------------------------------------------*/

	void DELAY_HARDWARE_One_Second(void){
	 unsigned char d ;
	 //Call DELAY_HAREWARE_50ms twenty times
	 for(d=0 ; d<20;d++){
	  DELAY_HARDWARE_50ms();
	 }
 
	}

 /*--------------------------------------------------------------*-
  DELAY_HARDWARE_50MS()
  Hardware delay of 50ms
  ***Assumes 12mhz 8051 (12 osc cycles) ***
  -*-------------------------------------------------------------*/
  void DELAY_HARDWARE_50ms(void){
   //Configure Timer 0 as a 16 bit timer 
   TMOD &= 0xF0; // Clear all T0 bits ( T1 left unchanged)
   TMOD |= 0x01; // Set required T0 bits (T1 left unchanged)

   ET0 = 0; //No interupts

   //values for 50ms delay
   TH0 = 0x3C; //Timer 0 intial value (High Byte)
   TL0 = 0xB0; //Timer 0 intial value (Low Byte)
   
   TF0 = 0 ;  //Clear overflow flag
   TR0 = 1 ;  //Start timer 0 
   while(TF0 == 0);//Loop until Timer 0 overflows (TF0 == 1)
   TR0 = 0 ;  //Stop Timer 0 
    
  }

  /*-------------------------------------------------------------*-
  --------------END OF FILE--------------------------------------
  -*-------------------------------------------------------------*/