Synth-DIY Yahoo! Groups Archives

Thread

Question regarding interrupt routine in AT90CAN128

2005-08-08 by Venkat Nagappan

Hi
     I have a question regarding interrupt routine in AT90CAN128 .

    When I try to increment the value of a register inside the interrupt 
routine , the register gives some random value .
    What should i do for this. Pls. help me.

bye
c.b.vijay

RE: [AVR-Chat] Question regarding interrupt routine in AT90CAN128

2005-08-09 by wbounce

Sounds like you need the volatile modifier in front of you variable
declaration
Ie 
volatile uint8_t msCount;

This tells the compiler that is the variable is modified outside of the
interrupt routine.

Show quoted textHide quoted text

-----Original Message-----
From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On
Behalf Of Venkat Nagappan
Sent: Monday, August 08, 2005 11:08 AM
To: AVR-Chat@yahoogroups.com
Subject: [AVR-Chat] Question regarding interrupt routine in AT90CAN128


Hi
     I have a question regarding interrupt routine in AT90CAN128 .

    When I try to increment the value of a register inside the interrupt

routine , the register gives some random value .
    What should i do for this. Pls. help me.

bye
c.b.vijay






 
Yahoo! Groups Links

RE: [AVR-Chat] Question regarding interrupt routine in AT90CAN128

2005-08-09 by Thomas Keller

On Tue, 2005-08-09 at 09:56 -0400, wbounce wrote:
> Sounds like you need the volatile modifier in front of you variable
> declaration
> Ie 
> volatile uint8_t msCount;
> This tells the compiler that is the variable is modified outside of
> the interrupt routine. 

   Or simply declare the variable as a global identifier.  Globally
declared variables are visible in all modules/files.

  Which C compiler is this, anyway?

tom

Re: [AVR-Chat] Question regarding interrupt routine in AT90CAN128

2005-08-10 by Brian Dean

On Tue, Aug 09, 2005 at 11:11:39AM -0500, Thomas Keller wrote:

>    Or simply declare the variable as a global identifier.  Globally
> declared variables are visible in all modules/files.

That would be insufficient.  The 'volatile' attribute lets the
compiler know that the variable could be modified outside the
compiler's realm of awareness.  Thus, it should not optimize accesses
to the variable by caching it's value in a register.  There are other
reasons to use volatile also.

But the OP specifically mentioned a "register" value which leads me to
believe that the problem is not a 'volatile' variable, but that
something else is modifying the register outside the interrupt
routine.  Probably just a case of not accounting for everything that
uses that particular register.

>   Which C compiler is this, anyway?

I don't think the OP said - I actually assumed assembly since he
mentioned "register" as opposed to a variable.

-Brian
-- 
Brian Dean
ATmega128 based MAVRIC controllers
http://www.bdmicro.com/

Re: [AVR-Chat] Question regarding interrupt routine in AT90CAN128

2005-08-10 by Venkat Nagappan

its with avr studio assembly language programming

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Thomas Keller wrote:

Show quoted textHide quoted text

> On Tue, 2005-08-09 at 09:56 -0400, wbounce wrote:
> > Sounds like you need the volatile modifier in front of you variable
> > declaration
> > Ie
> > volatile uint8_t msCount;
> > This tells the compiler that is the variable is modified outside of
> > the interrupt routine.
>
>    Or simply declare the variable as a global identifier.  Globally
> declared variables are visible in all modules/files.
>
>   Which C compiler is this, anyway?
>
> tom
>
>
>
> SPONSORED LINKS
> Atmel avr 
> <http://groups.yahoo.com/gads?t=ms&k=Atmel+avr&w1=Atmel+avr&w2=Microcontrollers&w3=Intel+microprocessors&w4=Pic+microcontrollers&w5=8085+microprocessor&c=5&s=115&.sig=UdYTrGL2FrE55fcuy5wZEQ> 
> 	Microcontrollers 
> <http://groups.yahoo.com/gads?t=ms&k=Microcontrollers&w1=Atmel+avr&w2=Microcontrollers&w3=Intel+microprocessors&w4=Pic+microcontrollers&w5=8085+microprocessor&c=5&s=115&.sig=lrlEOiO4YgeS8q8wlFKMDA> 
> 	Intel microprocessors 
> <http://groups.yahoo.com/gads?t=ms&k=Intel+microprocessors&w1=Atmel+avr&w2=Microcontrollers&w3=Intel+microprocessors&w4=Pic+microcontrollers&w5=8085+microprocessor&c=5&s=115&.sig=ukPztZmdOedN_8ChzX-5zA> 
>
> Pic microcontrollers 
> <http://groups.yahoo.com/gads?t=ms&k=Pic+microcontrollers&w1=Atmel+avr&w2=Microcontrollers&w3=Intel+microprocessors&w4=Pic+microcontrollers&w5=8085+microprocessor&c=5&s=115&.sig=ZLA3s52uCUS41MlZHTBMKg> 
> 	8085 microprocessor 
> <http://groups.yahoo.com/gads?t=ms&k=8085+microprocessor&w1=Atmel+avr&w2=Microcontrollers&w3=Intel+microprocessors&w4=Pic+microcontrollers&w5=8085+microprocessor&c=5&s=115&.sig=IxZk4rgmjbtS_sw6CPxrQg> 
>
>
>
> ------------------------------------------------------------------------
> YAHOO! GROUPS LINKS
>
>     *  Visit your group "AVR-Chat
>       <http://groups.yahoo.com/group/AVR-Chat>" on the web.
>        
>     *  To unsubscribe from this group, send an email to:
>        AVR-Chat-unsubscribe@yahoogroups.com
>       <mailto:AVR-Chat-unsubscribe@yahoogroups.com?subject=Unsubscribe>
>        
>     *  Your use of Yahoo! Groups is subject to the Yahoo! Terms of
>       Service <http://docs.yahoo.com/info/terms/>.
>
>
> ------------------------------------------------------------------------
>