To calculate a constant for a different crystal frequency

[lilimike]

Hi,

I am trying to get some information indicated in file "Elapsed_INT" from DT_INT
In the file it reffers to a link which does not exist possibly since this forum changed yesterday.

' ------------------------------------------------------------------------------
' To calculate a constant for a different crystal frequency - see this web page
' http://www.picbasic.co.uk/forum/showthread.php?t=2031
' ------------------------------------------------------------------------------

Is there any way to get to it?

Thanks

Mike

[Darrel Taylor]

That thread got lost about a year or so ago.
Fortunately, there's something much better from mister-e.

Use the Timer Helper app in this ...

PicMultiCalc V_1.3.1
http://www.picbasic.co.uk/forum/attachment.php?attachmentid=2957
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[lilimike]

Got it thanks,

I am trying to understand how to use it to calculate what I need, nonetheless it is hard enough for me to even know what I need but is there any tutorial/examples available?

Mike

[lilimike]

I think I will be ok with this after all.
The only thing I don't have a clue what it is for and/or how to apply is the value called "Reload(instr. Cycle)" but it doesn't seam to affect anything.


Mike

[Darrel Taylor]

The "Reload(instr. Cycle)" value is important for Long-Term accuracy.
It represents the number of Clock Cycles (instructions) that it takes to Reload the timer.

In the case of Elapsed_INT ... there are 7 cycles between the point where the timer is stopped until it's been reloaded and turned back on again.


; ----------------- ADD TimerConst to TMR1H:TMR1L
ADD2_TIMER macro
CHK?RP T1CON
BCF T1CON,TMR1ON ; Turn off timer
MOVLW LOW(TimerConst) ;1 1
ADDWF TMR1L,F ;2 1 ; reload timer with correct value
BTFSC STATUS,C ;3 1/2
INCF TMR1H,F ;4 1
MOVLW HIGH(TimerConst) ;5 1
ADDWF TMR1H,F ;6 1
endm

; ----------------- ADD TimerConst to TMR1H:TMR1L and restart TIMER1 ----------
RELOAD_TIMER macro
ADD2_TIMER
BSF T1CON,TMR1ON ;7 1 ; Turn TIMER1 back on
endm


7 is also the default number in mister-e's program, but different reload routines may take longer, or shorter times.

hth,

[lilimike]

That's great information.

Thank you

Mike