Em 11/6/2012 07:00, Michael Rigby-Jones escreveu:
>
> -----Original Message-----
>
> Em 8/6/2012 14:31, William "Chops" Westfield escreveu:
>> On Jun 8, 2012, at 4:54 AM, Ben Barwise wrote:
>>
>>> interrupt isr()
>>> {
>>> int off1 =3D 0;
>>> }
>> You'll need to make off1 a global variable, so that references to that n=
ame in the isr and references from the main code actually reference the sam=
e data.
>>
>> Then you'll probably need to make it "volatile" so that the compiler wil=
l be warned that it has to keep checking the value, instead of (for instanc=
e) moving it into a register at the start of main and just referring to tha=
t copy over and over again.
>>
>> BillW
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf =
Of Isaac Marino Bavaresco
> Sent: 08 June 2012 19:23
> To: Microcontroller discussion list - Public.
> Subject: Re: [PIC] Help using interrupts in High Tech C & 12F683
>
>> Do not forget to use a critical section (segment of code with interrupts
>> disabled) to access off1 from main code, otherwise you may get corrupted=
 data.
>>
>>
>> Isaac
> If access to the variable is atomic (e.g. it's a single bit or an aligned=
 byte wide value on a PIC) then a critical section should not be needed.
>
> Mike


Exactly, *atomic* operations don't need to be protected. Unfortunately,
most operations are not atomic, even on single bits or bytes.
For instance: if you need to check the current value and then change it,
then it is not an atomic operation anymore.
Also, his variable is 'int'.


Isaac

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