cannella
Newbie level 1

16f876a ra3 pin as digital
Recently i found a problem to menage the PORTA pins, in fact if i make the register config to:
ADCON1=0b10000101; //set RA0 and RA1 to analog, RA3 as Vref+, VSS as Vref-.
ADCON0=0b11000001; //analog conversion on the RA0 and internal RC for the A/D.
...and when i try to change the Vref+ by a trimmer doesn't change the reference range for the analog value on the RA0 pin, in this case LM35 temperature sensor.
What is the problem?
Recently i found a problem to menage the PORTA pins, in fact if i make the register config to:
ADCON1=0b10000101; //set RA0 and RA1 to analog, RA3 as Vref+, VSS as Vref-.
ADCON0=0b11000001; //analog conversion on the RA0 and internal RC for the A/D.
...and when i try to change the Vref+ by a trimmer doesn't change the reference range for the analog value on the RA0 pin, in this case LM35 temperature sensor.
What is the problem?