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/atta...achmentid=2957
<br>

[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