A/D converter with pic16f84, i need a help

look at these codes to do A/D conversion


INCLUDE "modedefs.bas"
trisb =%00000100
b0 var byte
low 1

start:
gosub serial_in
serout portb.3,2,[254,1]
pause 1
serout portb.3,2,[#b0]
pause 100
goto start
serial_in:
low 0

shiftin portb.2, portb.1, MSBPOST, [b0\9]

high 0
return




i attached the circuit diagram with
the A/D IC is ADC08031 and pic16f84

i used the same codes and circuit with A/D ADC0831 and that
is working well but with the ADC08031 does not work


any hints please ??