pic16f877 timer0 counter

pic16f877 counter

I have a simple question. How would I configure the TMR0 of the PIC16F877 to run on an external clock (32.786kHz). eventhough the chip will be running at 4MHz?or maybe even if it runs on the internal instruction clock cycle?how do i get the timer0 to produce an interrupt every 1 second?I am trying to implement a RTC using the timer0 counter.
please help!

timer0 pic16f877

Configurate the time0 module to use t0cki pin as time0 clock source

pic16f877 tmr0

16f877 has timer 1 why don't you use it???
it is dadicated tasks like that....

16f877 timer0

Hi,

Set this bits as folows:
Then every time you will get TMR0IF flag you will go the the interupt, there you will have to do:

Good luck.

tmr0 register

This is a replay to a PM that the user worte me. My answer was long and im sure some others whould want to read my explanation, so i posted it here

Hi,

First of all, if you think that i helped, then in the window where i wrote my answer any maybe in this one there is a buttom with Helped me writen on it. Please click that, so i will know that you did appritiate my help.

Regarding your questions:

what bits do i set within the INTCON register?

Click to expand...

Ok, If you will look at the PIC16F87XA.pdf the you will see in FIGURE 14-10: INTERRUPT LOGIC the table what you need to enable inorder to get your interupt.
Also go to 2.2.2.3 INTCON Register and there you will see what bits you need to set on ( =1 ) and what you need to see off (=0 ).

also,if i want to use the 4MHz crystal i am currently using and trigger the timer using the internal instruction cycle=1us or 1mHz(if im not mistaken),how do i go about getting the clock to work as desired

Click to expand...

If you will look at FIGURE 5-1: BLOCK DIAGRAM OF THE TIMER0/WDT PRESCALER in the data sheet then you will see what you need to turn ON or OFF for the clock to work from the internal 4MHz. BUT, you need to remember this. The internal clock needs to be divided by 4 { each instruction will be 1/( 4MHz / 4MHz ) }.
So lets say you will use the prescaler at max, thats 1:256 and using the internal clock at 4MHz then will get this timing:
4MHz/4MHz = 1MHz = (1 / 1MHz ) = 0.000001 Sec.
The TMR0 will incrament every prescaler * 1MHz = 256 * 0.000001 = 0.000256 Sec
To find out when you will get an interupt if you will load 0x30 to TMR0 register:
TMR0 max register - Var = 0xFF - 0x30 = 0xCF
Interupt = 0xCF * 0.000256 = 0.052992 Sec.
So, if you will load this settings, you will get an interupt every 0.052992 of the second when using the OSC of 4MHz.

Good luck.