Problem interfacing AT89C52 and HY62256(S-Ram)

[vinash]

Hi,
I have tried to interface ADC0804 and HY62256(S-ram) to AT89C52 microcontroller. The whole idea is to do an A/D conversion using ADC 0804 and than storing the data input to the SRAM. The code that i had developed is below for reference. It does not seem to work. Could someone please tell me if there is anything wrong with my code. Thank you.

#include <reg52.h>

void delay(void);
unsigned char xdata * data addr = 0x0000; // declares a pointer staring from external memory address of 0x0000
sbit WRITE=P3^0; // defining the WR and INTR pins
sbit INTR=P3^2 ;// The INTR pin is connected to the INTO pin, so that whenever it goes low, it cause an interrupt
sbit LED=P3^1;
unsigned int advalue,value,j;


void ex0_isr (void) interrupt 0 // interrupt that is activated whenever P3^2 goes low
{ P1=0xFF; // declaring P1 as input data after A/D conversion
advalue=P1; // assigning the input bits (A/D bits) to advalue
if(addr!=0xFFFF) // keep on storing the 8 bit values obtained from the ADC in address starting from 0x0000 till
// the S-RAM gets full.
{LED=1; // to check whether there is any conversion
for(j=0;j<2000;j++);
*addr++ =value;
LED=0; //to check whether there is any conversion
delay(); // delay function
}

else
{
EX0 =0; // If the S-ram is full, disable external interrupt 0 and the Global interrupt flag
EA=0;
}
}


void main(void){
EX0 = 1; // Enable EX0 Interrupt, this function is to enable (set) or disable(clear) External intrrupt 0
EA = 1; // Enable Global Interrupt Flag
IT0=0; // Interrupt 0 type control bit.Set/cleared by software to specify falling edge/low level triggered External interrupt
P1=0xFF; // Declaring P1 as an input

while(1) {

WRITE=0; // AD conversion;
WRITE=1;
while(INTR==1);
delay();

}
}



void delay (void) // Delay function using Timer 0 for 50ms.
{
TMOD &=0xF0;
TMOD |=0x01;
ET0 =0;
TH0 =0x3C;
TL0 =0xB0;
TF0 =0;
TR0 =1;
while(TF0==0);
TR0=0;

}