if in a interrupt rountine with a 80c51

[zweitakt1973]

hi there,

i have got a problem with a 80c51 processor and Keil C Compiler:

when i use a "if"-structure in a interrupt routine, it is ignored: the
part inside the if-structure will always be executed, even if the
state is false. Can anyone help me?Here a code example:

if (CCF1 = 1)
{
CCF1 = 0;

P0_5 = 1;
}

the code inside is always executed, even if CCF1 = 0.

???why

[Keith Thompson]

zw**********@yahoo.de writes:

i have got a problem with a 80c51 processor and Keil C Compiler:

when i use a "if"-structure in a interrupt routine, it is ignored: the
part inside the if-structure will always be executed, even if the
state is false. Can anyone help me?Here a code example:

if (CCF1 = 1)
{
CCF1 = 0;

P0_5 = 1;
}

the code inside is always executed, even if CCF1 = 0.

Consider the difference between '=' and '=='.

The comp.lang.c FAQ is at <http://www.c-faq.com/>. See question 20.22.

--
Keith Thompson (The_Other_Keith) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <* <http://users.sdsc.edu/~kst>
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"

[jacob navia]

zw**********@yahoo.de wrote:

hi there,

i have got a problem with a 80c51 processor and Keil C Compiler:

when i use a "if"-structure in a interrupt routine, it is ignored: the
part inside the if-structure will always be executed, even if the
state is false. Can anyone help me?Here a code example:

if (CCF1 = 1)
{
CCF1 = 0;

P0_5 = 1;
}

the code inside is always executed, even if CCF1 = 0.

???why

You are assigning 1 to CCF1, not testing for equality!!!
Then, since the result of the assignment is 1, the
if always succeeds and you always execute the if part.

[zweitakt1973]

On 27 Jul., 09:27, [e-mail] wrote:

hi there,

i have got a problem with a 80c51 processor and Keil C Compiler:

when i use a "if"-structure in a interrupt routine, it is ignored: the
part inside the if-structure will always be executed, even if the
state is false. Can anyone help me?Here a code example:

if (CCF1 = 1)
{
CCF1 = 0;

P0_5 = 1;

}

the code inside is always executed, even if CCF1 = 0.

???why

Thank you for answers. You helped me a lot!