Where do functions with no input or output return variables?

Hi i have this piece of code and was wondering where it returns the value?

Code:

void ReadPOT(void)
{
    ADCON0bits.GO = 1;              // Start AD conversion
    while(ADCON0bits.NOT_DONE);     // Wait for conversion
    return;
}//end ReadPOT

i just wanted to check also that this means that the number 1 is put into the member named GO.

I'm not sure how NOT_DONE as a member would detect whether the AD conversion has completed - does anyone have any idea? how can using a dot operator here check a bit inside the ADCON0 register?

Thanks

ADCON0bits would have to be globaly declared within the same source file (or by extern).

It would probably need to be declared 'volatile' as well in order to make sure the bit was tested over and over.

Originally Posted by phoenix23

Hi i have this piece of code and was wondering where it returns the value?

Code:

void ReadPOT(void)
{
    ADCON0bits.GO = 1;              // Start AD conversion
    while(ADCON0bits.NOT_DONE);     // Wait for conversion
    return;
}//end ReadPOT

i just wanted to check also that this means that the number 1 is put into the member named GO.

I'm not sure how NOT_DONE as a member would detect whether the AD conversion has completed - does anyone have any idea? how can using a dot operator here check a bit inside the ADCON0 register?

A guess is that ADCON0bits is declared as a structure with bitfields, and some of the names of these bitfields are GO and NOT_DONE. And I would further guess that some implementation specific method is used to absolutely place this structure atop the location of a status and control register for A/D conversion. And as Salem mentioned, it is also likely volatile qualified to keep the optimizer away from the idle loop code. All of this magic is probably found in some platform-specific header.

So this:

Code:

ADCON0bits.GO = 1;              // Start AD conversion

is used to set that particular bit in the register (which starts the A/D).

Then this:

Code:

while(ADCON0bits.NOT_DONE);     // Wait for conversion

is an idle loop that waits for the A/D conversion to complete, at which time the bit corresponding to NOT_DONE is cleared -- by the micro.