BSF RA1 overwrites RA0

[Guest]

Hello all,
we tested this little code for the 12F675:

----------------------------------------
#if defined(__PCM__)
#include <12F675.h>
#include <12F675io.h>
#fuses INTRC_IO,NOWDT,NOMCLR,NOPROTECT,NOBROWNOUT,NOPUT
#endif

int1 oo;

void main()

{
r0io=0; //Port RA0 is Output (IO- Register)
r1io=0; //Port RA1 is Output (IO- Register)

while(1)
{
oo=~oo; //xor bit oo
ra0=oo;
ra1=oo;
}
}

-----------------------------------------

The behavior of the code after download the hex to Pic is as follow:

First, RA0 ist setting everything is fine.
But if the RA1 is setting the RA0 goes low with the rising Edge of RA1.

Whats the problem?
And why cant the Compile xor RA0 directly like this RA0=~RA0


Thank you all in advance and sorry for my bad english, im German
Frank

[PCM programmer]

What is your version of the compiler ?

[Ttelmah]

It could be a classic 'read modify wite' problem. You say that RA0 goes high. How high?. To be 'seen' as high, RA0, needs to be at 0.25Vdd+0.8v. If there is significant capacitance, or a reasonable load on the pin, it may not be actually reaching this voltage. Then when you set RA1, the processor actually reads the port, and sets RA0 in this value, then writes the result back out to the port. If the pin is not high enough, it will be turned off at this point...

Best Wishes