Making a timer, 32.768kHz+555+DT_INT. Good idea?

[Darrel Taylor]

There's the problem ...

TMR1L=0
TMR1H=128
@ INT_RETURN

By the time it gets all the way through the interrupt handler, another tick or two may have been counted by Timer1.
That gets lost when you reload both bytes of the Timer.

For 32768 crystals, the reload is really simple ...

TMR1H.7 = 1

And it's best to put it at the beginning of the handler.
Although in your case, the handler is fast enough it won't matter were it is.

[financecatalyst]

There's the problem ...

TMR1L=0
TMR1H=128
@ INT_RETURN

By the time it gets all the way through the interrupt handler, another tick or two may have been counted by Timer1.
That gets lost when you reload both bytes of the Timer.

For 32768 crystals, the reload is really simple ...

TMR1H.7 = 1

And it's best to put it at the beginning of the handler.
Although in your case, the handler is fast enough it won't matter were it is.

I did TMR1H.7=1, but the code is not entering the interrupt. I checked it with changing it to TMR0, it works. Am I making a mistake in setting up timer1?

[Darrel Taylor]

I did TMR1H.7=1, but the code is not entering the interrupt. I checked it with changing it to TMR0, it works. Am I making a mistake in setting up timer1?

T1CON=%00001010 ; Timer 1 settings towards the beginning of the code

You might want to turn the Timer ON.

[financecatalyst]

Sorry Darrel, I put Timer1 On now, but the problem is still there.

T1CON=%00001011
Further investigation revealed that this bit is the problem. Looks like in the simulation software I need to look into crystal setup again. I tried with this bit cleared and it worked fine.

[Darrel Taylor]

With that bit cleared, Timer1 is clocked from FOSC/4 instead of the Timer1 oscillator.

What simulator are you using?

[financecatalyst]

I am using Proteus 6.9 (which I am also new to).
Screenshot of the setup is attached.
It is not working with external clock settings on timer 1
I tried changing capacitor values, crystal values but no response.

[Darrel Taylor]

Hmmm, apparently the Timer1 oscillator doesn't work.

Instead ... exclude the crystal and caps from the simulation, and add a clock generator on the T1OSI input.



Set it up like this.