delay_t0.c

CODE for embedded C ,hand coding version

/*----------------------------------------*-
  Delay_To.c (v1.00)
  ------------------------------------------
  Simple hardware delays based on To
  -*----------------------------------------*/
  #include "Main.H"
  //-------------Private constants----------
  //Timer preload values for use in simple(hardware) delays
  //-Timers are 16-bit,manual reload('one shot')
  //
  //NOTE: These values are portable but timings are 'approximate'
  //      must be checked by hand if accurate timing is required

  //
  //Define Timer 0/1 reload values for ~1msc delay
  //NOTE: Adjustment made to allow for function call overhead etc
  #define PRELOAD01 (65536-(tWord)(OSC_FREQ/(OSC_PER_INST * 1020)))
  #define PRELOAD01H (PRELOAD01/256)
  #define PRELOAD01L (PRELOAD01 % 256)

  /*---------------------------------------------*-
  Delay_To()
  Function to generate N millisecond delay (approx)
  Uses Timer 0 (easily adapted to Timer 1)
  -*-----------------------------------------------*/
 void Delay_T0_Wait(const tWord N)
 {
   tWord ms;
   //configure Timer 0 as a 16-bit timer 
   TMOD &= 0xF0 ; //Clear all To bits (T1 left unchanged);
   TMOD |= 0x01 ; //Set required T0 bits (T1 left unchanged);

   ET0 = 0; //No interupt
   //Delay value is *approximately* 1ms per loop
   for (ms = 0 ;ms<N;ms++){
    TH0 = PRELOAD01H;
	TL0 = PRELOAD01L;
	TF0 = 0;
	TR0 = 1;
	while(TF0 == 0);
	TR0 = 0;
   }

 }

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