I need your help please

[Alibataineh]

Hello everyone,
Hope you're doing well .
I study power engineering and this is my third year. To be able to graduate I have to pass micro-controller course, even though it's not related to my field of study.
Anyway, I was searching online and I'm really thrilled to find this site.
I need your help regarding programming TMR0 as counter. Does anyone know how to write a program to count the number of negative pulses received on one of the PIC 6F877 I/O pins ?
Thank you in advanced,
You'd really save my life if you know the code
Peace

 

[Alibataineh]

Someone told me this would help me to actually count the positive pulses :

main:

; 1. configure tmr0

movlw b’10111000’
movwf option_reg

; 2. Set up ports
movlw 0x00 ;
Movwf trisd
movlw B’00011111’ ;
Movwf trisa ;

; 3. Mask 2nd digit of TMR0

loop:movf trm0,w ;
Andlw 0x0f;
call segment
movwf portd ;
goto loop ;



Is that true ? What about the negative pulses ?

 

[be80be]

All you do is change the option register bit 4 to 0
I don't want you to think I'm be smart but there a pdf called the 16F877 datasheet if you look at timer0
It tells you what setting to use and how to use it.

I read the datasheet even if I think I no the setting I still read it, You'll learn a lot from it trust me on that one.

; 1. configure tmr0
    ; movlw b’10111000’        ; this setting is low to high
     movlw b’10101000’         ; you change bit 4  this reads high to low 
     movwf option_reg

; 2. Set up ports
     movlw 0x00 ;
     Movwf trisd
     movlw B’00011111’ ;
     Movwf trisa ;

; 3. Mask 2nd digit of TMR0

     loop:movf trm0,w ;
     Andlw 0x0f;
     call segment
     movwf portd ;
     goto loop ;

This is really good it's in C but it tells how the timer0 works https://www.electro-tech-online.com/custompdfs/2012/12/51682A.pdf

And this is real good about timer0 in asm https://www.electro-tech-online.com/custompdfs/2012/12/PIC_Mid_A_4.pdf