> Shouldnt the #use delay(clock=10000000) be 20000000 as I am using a 20MHz clock?

Yes.

> Also, the delay of 100ms.  Why have you chosen this, is it the time
> for the pic to register and process the analogue to digital
> conversion, so after 100mS it is ready to sample again?

Nope, it's just a loop delay - the PIC reads the ADC value and prints
every 100mS.  You could just as easily use a one-second delay or whatever.

> I assume that the result of the conversion is stored in value. Say for
> example I nputed 2.5v into the PIC how can I actually see what this
> value is to ensure that the A2D is functioning correctly.

In the example given, the line "value = Read_ADC();" will put the ADC
reading into the variable named "value".  Actually in that particular case
you'll only get an 8-bit result, since value is an int.  I would use a
long and make sure to set "#device PIC16F877 ADC=10" to get all 10 bits.
Here's a snippet of code from one of my projects that uses trhe ADC:

#device PIC16F877 *=16 ADC=10
#use delay (clock=20000000
#define volt_input 1                    // Analog input from VMM
#define amp_input 0                     // Analog input from shunt isolation amp
setup_adc_ports(A_ANALOG);              // Set up analog pins setup_adc_ports
                                        // (RA0_RA1_ANALOG_RA3_REF);
setup_adc(ADC_CLOCK_DIV_32);            // Set up ADC clock

temp = 0;
for(x=0;x<16;x++) {
        set_adc_channel(amp_input);
        delay_ms(1);                    // Chosen somewhat arbitrarily.
                                        // You actually only need a few
                                        // microseconds sample time.
        temp += read_adc();
}


What you'll get is a number from 0 to 1023, corresponding to the input
voltage compared to the reference voltage.  In other words, if Vref = 5V
and Vin = 2.5V, the ADC reading will be 512.

Hope this helps...

Dale

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