incrementing up to ... then reset

[johnl69]

Hi

I cant seem to work out how to increment a registry value from 0 to 24 and then have this registry reset to 0 and to display this on a lcd screen.

What im trying to do is to enter a time into a pic to be compared for an alarm, the problem I have is as I press the button to increment the time the display goes from 0 - 9 then through the whole ascii code.

Any help would be appreciated

john

 

[Henry T]

What language are you programming it in and wich pic?
But you have to convert your HEX code to a BCD code, there are examples galore of that around here I bet.

 

[johnl69]

Sorry I forgot to put I right in assembly and pic 16f877

I can do the bcd to hex conversion but my problem is getting the value to stop at 24 and then reset to 0 at the next button press

 

[Henry T]

Euhm, long time since I worked in asm for pics, but do they have a compare function?
Or else you could decrement a register every time you increment and when that hits 0 you can do whatever... BTFSZ i believe that was?

 

[picasm]

To reset the count back to zero if "reg" increments higher than 24:

    incf    reg,F               ;Inc the reg
    movlw    D'25'            ;load with 25 to check against reg
    xorwf    reg,W            ;Xor but dont affect the reg yet
    btfsc    STATUS,Z       ;Skip if not 25
    clrf    reg                   ;Reached 25 so set reg back to 0
    movf    reg,W            ;Get the new value of reg into w to send to your display

 

[Henry T]

btfsC it was appearantly
xor'ing it will work too I guess, and then when they are equal, the Z flag gets cleared or something? Pff i need to get back into my PicASM, it's all 8051 at our school now, and there are WAYY too many instructions, wich is nice too mind you, but a risc is a little different eh :d

 

[Pommie]

Shouldn't you be counting from 0 to 23 or 1 to 24. Counting from 0 to 24 will result in a 25 hour day!!

Mike.

 

[johnl69]

Thanks alot guys for your help,

Pommie, Yes it should be 0 - 23 and then 0 - 59 but it was late and I was still feeling the effects from the anastetic