TMR2 not working..

[sirvo]

Hello..

I'm trying to make 16f88 'interrupt' every 500ms. TMR0/1 are busy. So, I've set TMR2 to interrupt every 1ms and then count var TMR2_clock till 500. But, it is interrupting every 3ms or something... Would you help me?

'------- initial -------------------- 
TMR2_clock   VAR   WORD
OPTION_REG = %00000000 
INTCON 	= %11000000 ' enable interrupts
TRISB = %00000000 ' portb all output
TRISA = %00111111 ' some analog inputs
ANSEL = %00001111 ' some analog inputs
CMCON = %00000111 ' turn of comparators
ADCON1 = %10000000' right justified
T2CON = %00000011 ' TMR2 prescale 1:16
'--------------------------------------------------- 
TMR2_clock = 0
    
    
    Lcdout $FE,1 ' clear screen
    
    PR2 = 194 ' load tmr2 PR2 to reset every 1ms
    PIE1.1 = 1 ' enable TMR2 interrupt
    PIR1.1 = 0 ' disabled interrupt flag - TMR2
    T2CON.2 = 1 ' turn TMR2 on

    ON INTERRUPT GOTO tick

MAIN:
' do nothing
GOTO MAIN

    DISABLE      
tick:
    PR2 = 194 'reload PR2
    TMR2_clock = TMR2_clock + 1
    Lcdout $FE,$A0, DEC TMR2_clock
    IF TMR2_clock = 500 THEN 
         TMR2_clock = 0
         ' Set some flag..
    ENDIF
    PIR1.1 = 0
resume
    ENABLE

Thanks..!

Sylvio

[Darrel Taylor]

The default LCD_COMMANDUS is 2000 us. (2 ms)
So moving the cursor to a specific location within the ISR makes it wait that much longer before it Resume's.

Add in the 50us for each character displayed, and the 1ms for the interrupt itself, and you get "3ms or something...".

HTH,

[sirvo]

Right.. i just put the LCDOUT command to compare the count with my hand watch. So, the routine is correct.. thanks Darrel.

Sylvio

[Darrel Taylor]

... So, the routine is correct..

Good to go ...
One thing to note ...
You don't need to reload PR2 each time. It doesn't change.
<br>

[sirvo]

0.o I've read that a thousand times and still reloaded..Thanks again..

Sylvio

[sirvo]

HI Again... I have tried again taking the LCDOUT command out of interrupt routine and putting inside the MAIN sub. NOthing! It is running crazy and I've also tried setting postscaler 1:16 or/and prescaler 1:16 and still nothing. Does the code look really correct? What I want is to set any flag every 500ms using TMR2... A little help please?

Thanks again.. Sylvio,

'------- initial -------------------- 
TMR2_clock   VAR   WORD
OPTION_REG = %00000000 
INTCON 	= %11000000 ' enable interrupts
TRISB = %00000000 ' portb all output
TRISA = %00111111 ' some analog inputs
ANSEL = %00001111 ' some analog inputs
CMCON = %00000111 ' turn of comparators
ADCON1 = %10000000' right justified
T2CON = %00000011 ' TMR2 prescale 1:16 --> TESTED WITH POST and PRESCALER (1:16)
'--------------------------------------------------- 
TMR2_clock = 0
    
    
    Lcdout $FE,1 ' clear screen
    
    PR2 = 194 ' load tmr2 PR2 to reset every 1ms
    PIE1.1 = 1 ' enable TMR2 interrupt
    PIR1.1 = 0 ' disabled interrupt flag - TMR2
    T2CON.2 = 1 ' turn TMR2 on

    ON INTERRUPT GOTO tick

MAIN:
    Lcdout $FE,$A0, DEC TMR2_clock ---> CHANGED
GOTO MAIN

    DISABLE      
tick:
    TMR2_clock = TMR2_clock + 1
    IF TMR2_clock = 500 THEN 
         TMR2_clock = 0
         ' Set some flag..
    ENDIF
    PIR1.1 = 0
resume
    ENABLE