Problem in Reading the O/P of an ADC0804

Hi
I have connect an ADC0804 to an AT89c52 to port P1 and the RD,WR, INT to P2. and the output is display on digtial trainner but If I increase the IN voltage to the ADC the display is not changing. The following is the code i am using Keil can any tell what is the problem

#include<reg51.h>
xdata unsigned char var _at_ 0x9000;


void display();
void adc();


main()
{



P1=0xFF;

while(1)
{
adc();
}
}

void adc()

{
P2=0x00;
P2=0x40;
if(P2==0x80)
{
P2=0x00;
var=P1;
display();
P2=0x20;

}


}


void display()
{
#pragma asm
push dph
push dpl
push acc
push b

mov dptr,#9000h
movx a,@dptr
mov 60h,a
lcall 019bh
pop b
pop acc
pop dpl
pop dph
#pragma endasm

}