红外解码问题，请帮我看看

弄红外解码好多天了，总是遇到问题，大家帮我看下我这样弄有什么问题？

//cpu3?ê??ˉ
void cpu_init(void)
{
TMOD = 0x11 ;
IP = 0x2;
IT0 = 1;
EX0 = 1;
EA = 1;
IRstate = IR_EVENT;
}

void IRint() interrupt 0
{?

switch(IRstate)
{
case IR_EVENT:

if(P3_2 == 0)
{
// TR0 = 0;
TL0 = 0;
TH0 = 0;
TF0 = 0;
ET0 = 1;
// TR0 = 1;
while(P3_2 == 0)
{
;
}
//TR0 = 0;
IR_Low = TH0 ;
IR_Low = (IR_Low << 8) + TL0;

if((IR_Low > 6451) && (IR_Low < 10137))
{
P1_0 = 1;
}
TL0 = 0;
TH0 = 0;
// TR0 = 1;
ET0 = 1;
IRstate = IR_START;
}

break;
case IR_START:
TR0 = 0;
IR_High = TH0;
IR_High = (IR_High << 8) + TL0;

if((IR_High > 3225) && (IR_High < 5068))
{
P1_0 = 1;
}
TH0 = 0;
TL0 = 0;
TR0 = 1;
while(P3_2 == 0)
{
;
}
TR0 = 0;
IR_Low = TH0 ;
IR_Low = (IR_Low << 8) + TL0;
if((IR_Low > 368) && (IR_Low < 645))
{
// P1_0 = 1;
}
TL0 = 0;
TH0 = 0;
TR0 = 1;
IRstate = IR_TEMP;
break;
case IR_TEMP:
TR0 = 0;
IR_High = TH0;
IR_High = (IR_High << 8) + TL0;

if((IR_High > 1382) && (IR_High < 1658))
{
P1_0 = 1;
}
else if((IR_High > 368) && (IR_High < 645))
{
P1_0 = 1;
}
break;
case IR_SYNC:

break;
default:
// IRstate = IR_EVENT;
break;
}


}?

我的想法是进入外部中断后使用2个变量记录在高低电平时间断的计数，使用T0计数，每次进入外部中断读取时间赋值为IR_High，这事电平为低电平，然后重新启动T0，等待电平变为高电平后有读取计数赋值为IR_Low，然后计算在协议的各个时间段内的脉冲数，例如引导码9ms我采用 （11.0592/12）*9*1000 = 8294，我用IR_Low去和这个数比较，弄个误差范围，在8ms-10ms范围内比较，请问这样有什么错误？我弄的总是不对。