SOMEBODY HELPS ME

I write a small code in C to drive LCD ht1621 and it seemd OK but I can only write but not read.Although I set bit P1.6 to make it read OK but I can not get the data from LCD.
I write a small code in ASM and i can both read and write.
Could you tell me how to read from pin?
I include my C code and I need your help
#include<reg51.h>
#include<intrins.h>
#define READ_ID 0xC0
#define WRITE_ID 0xA0
#define COMMAND_ID 0x80
#define SYS_DIS 0x00
#define SYS_EN 0x01
#define LCD_OFF 0x02
#define LCD_ON 0x03
volatile unsigned char idata m _at_ 0x56;
volatile unsigned char idata n _at_ 0x57;
volatile unsigned char idata dt _at_ 0x58;
sbit C=P3^3;
sbit W=P3^4;
sbit R=P3^2;
sbit DATA=P3^5;
sbit IRQ=P1^6;
sbit SCL=P1^5;
sbit SDA=P1^4;
void delay()
{
_nop_();
_nop_();
_nop_();
}
void start()
{
C=0;
_nop_();
_nop_();
}
void stop()
{
C=1;
_nop_();
_nop_();
}
void send_id(unsigned char c)
{
unsigned char i;
for(i=3;i>0;i--)
{
W=0;
_nop_();
_nop_();
_nop_();
if((c&0x80)==0x80)
DATA=1;
else
DATA=0;
W=1;
_nop_();
_nop_();
_nop_();
c=c<<1;
}
}

void send_command(unsigned char c)
{
unsigned char i;
start();
send_id(COMMAND_ID);
for(i=9;i>0;i--)
{
W=0;
_nop_();
_nop_();
_nop_();
if((c&0x80)==0x80)
DATA=1;
else
DATA=0;
W=1;
_nop_();
_nop_();
_nop_();
c=c<<1;
}
stop();
}

void send_address(unsigned char c)
{
unsigned char i;
for(i=2;i>0;i--)
{
c=c<<1;
}
for(i=6;i>0;i--)
{
W=0;
_nop_();
_nop_();
_nop_();
if((c&0x80)==0x80)
DATA=1;
else
DATA=0;
W=1;
_nop_();
_nop_();
_nop_();
c=c<<1;
}
}
void read_byte()
{
unsigned char c;
for(c=4;c>0;c--)
{
R=0;
delay();
R=1;
delay();
if(DATA)
{
dt|=0x80;
}
dt>>=1;
}
}
void read_data()
{
start();
send_id(READ_ID);
send_address(32);
read_byte();
stop();
}

void send_data(unsigned char c)
{
unsigned char i;
for(i=4;i>0;i--)
{
W=0;
_nop_();
_nop_();
_nop_();
if((c&0x80)==0x80)
DATA=1;
else
DATA=0;
W=1;
_nop_();
_nop_();
_nop_();
c=c<<1;
}
}
void display_data()
{
start();
send_id(WRITE_ID);
send_address(m);
send_data(n);
stop();
delay();
}
void clear()
{
unsigned char i;
start();
send_id(WRITE_ID);
send_address(0x00);
for(i=128;i>0;i--)
{
W=0;
_nop_();
_nop_();
_nop_();
DATA=0;
W=1;
_nop_();
_nop_();
_nop_();
}
stop();
}
void main()
{
unsigned char c;
send_command(SYS_EN);
send_command(43);
send_command(LCD_ON);
clear();
EA = 0;
m=32;
n=0x80;
display_data();
c=read_data();
while(1)
{
}
}