:: I think he was being
:: sarcastic with the C

I didn't even mention 'c' !

Now it is true that as it stands the algorithm I was talking about 
counts in seconds, and from this any count or period is possible.  A 
little jiggery pokery by extending the algorithm to possibly 32 bits 
rather than 24 ought to work.

I'm really not interested in trying this out for myself, so someone 
else will have to prove or disprove the theory.

And for anyone who moans about the lack of comments - tough! The 
information commented is on my website and in the Piclist Archives by 
the originators of the algorithm.

Freq = 6.167
clk = 6.167/ 4 = 0x178676

For a period divide the above further by the period required.

 tickHi = 0x17
 tickMid = 0x86
ticklo = 0x76

add 1 to tick mid, then countdown tickMid until it is zero

movf tickmid,F
btfsc STATUS,Z                                                          
decf tickhigh,F                                                         
decfsz tickmid,F                                                        
goto end of interrupt                                                   
movf tickhigh,F                                                         
btfss STATUS,Z                                                          
goto end of interrupt                                                   
tickhigh = COUNTH                                                       
tickmid = COUNTM                                                        
ticklow = ticklow + COUNTL                                              
btfsc STATUS,C                                                          
tickmid+=1         ; One second has passed.     

In 'C'

void Interrupt()
{
  


  
 if(INTCON&(1<<T0IF)) 		        // Test TMR0 interrupt flag
  {
    #asmline bcf INTCON,T0IF           ;  Clear TMR0 interrupt flag
    		
       
    if(TickMid!=0)			//Has TickMid reached zero
      {
    	if(--TickMid!=0)	
        return;               	        //if not decrease and check for 
zero
      }
    else				//Tickmid was zero so decrease TickHigh
      {
    	 --TickHigh;
    	 if(--TickMid!=0);		//Has Tickmid reached zero now?	
     	 return;
      }	
     
     if(TickHigh==0)			//TickMid is zero so check TickHigh if
       { 				//zero reload counter
          TickHigh=COUNTH;
          TickMid=COUNTM;
          TickLow+=COUNTL;		//Load counter with initial+ remainder
          #asmline btfsc STATUS,C	;Has a carry occurred from low to 
mid
          TickMid++;			//yes so increase TickMid
          sec++;
       }    
  }
   
    
}                                                       

--
cdb, colin@btech-online.co.uk on 29/01/2009
 
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