ADC problem

[NacNud]

Hello,

First I want to say that this is a nice forum finding solutions for PBP.

Here is my queston about an Analog to digital conversion.
I want to put an conversion in the variable word_temp_int, but this ain't seem to work. Every result of the AD conversion is 0.
Using a PIC16F870.

This code is in my interrupt routine, the routine is 500 ms. The varaiable word_wachttijd_aantal is decreased with every interrupt.

if (word_wachttijd_aantal == 12) and (byte_status == 1) then
   adcon0.0 = 1                            ' AD converter on
endif
if (word_wachttijd_aantal == 11) and (byte_status == 1) then
   word_pot_adc = 0                     ' reset value potmeter
   adcon0.2 = 1                         ' start AD conversion
endif                
if (word_wachttijd_aantal < 11) and (byte_status == 1) then
   if adcon0.2 == 0 then                   ' test AD conversion ready
      word_temp_int.highbyte = ADRESH      ' store AD value
      word_temp_int.lowbyte = ADRESL       ' store AD value
      word_pot_adc = word_pot_adc * 9      ' some calculations
      word_pot_adc = word_pot_adc + word_temp_int
      word_pot_adc = word_pot_adc / 10
   endif
   adcon0.2 = 1                            ' start new AD conversion
endif

The AD converter is put on when word_wachttijd_aantal is equal to 12.
500 ms later the AD converter is started when word_wachttijd_aantal is equal to 11.
500 ms later the AD converter is stored in word_pot_adc because word_wachttijd_aantal is less than 11 and adscon0.2 is equal to 0 a long time ago.
After the AD value is stored in word_pot_adc a new AD conversion is started.

If I put de code untherneath here at the same place it works fine.

test:
   adcon0.0 = 1                            ' AD converter on
   pause 500                               ' wait 500ms is
   adcon0.2 = 1                            ' start AD conversion
ADC:	
   pause 5                                 ' wait 5ms aquisition time
   if adcon0.2 = 1 Then ADC                ' test if AD conversie is ready             
   word_pot_adc.highbyte = ADRESH          ' store AD value
   word_pot_adc.lowbyte = ADRESL
   adcon0.0 = 0                            ' AD converter off
goto test