PIC16f877a- restting TMRIH and TMRIL registers

[crush]

Hi all,
trying to reset the values on TMRIH and TMRIL to 0x00.

Cant seem to do this.
I tried TMR1L, TMR1H =0x00;
i tried turnin timer1 on and off by setting the TMRION.

i want to rest the registers as i am using the capture function (CCP1) which reads the values from the Timer1 registers when an event occurs(falling edge).

I am trying to find the time between two falling edges, so im loading the values captured at each event into two variables and calculating the time between them

I want to rest the registers to remove the hassle of having to account for the overflow.

any ideas?

 

[Nigel Goodwin]

Have you tried reading the datasheet?.

Resetting of Timer1 Register Pair
(TMR1H, TMR1L)
TMR1H and TMR1L registers are not reset to 00h on a
POR, or any other RESET, except by the CCP1 and
CCP2 special event triggers.
T1CON register is reset to 00h on a Power-on Reset,
or a Brown-out Reset, which shuts off the timer and
leaves a 1:1 prescale. In all other RESETS, the register
is unaffected.

 

[crush]

Have you tried reading the datasheet?.

Yup i did read the datasheet and the part u mention. And as it says it cannot be reset, even on a power on reset.
And though i am using the CCP1, im not using the special event, so it wont reset it.

I was wondering if there was a programming trick around it??

 

[picasm]

I think you are getting confused by the data sheet.

The ASM commands to reset these regs are just:

CLRF TMR1L
CLRF TMR1H

(It is always best to clear TMR1L first as shown so that TMR1H cannot increment due to a TMR1L overflow whilst you are clearing them.)

 

[gramo]

can someone give a brief descroption on the TMR1 on pics, not the full datasheet copy and paste, just a general description of what it does and how to use it

 

[Nigel Goodwin]

can someone give a brief descroption on the TMR1 on pics, not the full datasheet copy and paste, just a general description of what it does and how to use it

I would suggest downloading the 'Midrange Reference Manual' from MicroChip, or even just the Timer section - that should explain all you need to know.