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Aim : To generate a pulse of 4ms using a Timer1.(50% duty cycle) i.e. 4ms ON time and 4ms OFF time

Using Timer 1 the reload values calculated are  as follows

4ms*11.0592M = (FFFF- Reload value)*6
so there fore Reload value = E333.

This was the value I loaded into the program and when I saw output on P1.1 the ociloscope showed 8ms.

Now Problem : is (FFFF-Reloadvalue)*12 instead of 6.But data sheet shows osc/6.Here is my program : Please help me.

Code Select Expand

sbit port = P1^1;
   void main(void)
   {
    WDTC = 0x00;
CMOD = 0x00;
PCON = 0x00;
P1 = 0xFF;
TMOD = 0x10;
TCON = 0x00;
TL1 = 0x33;
TH1 = 0xE3;

TR1 = 1; // Start the Timer1
EA = 1;
ET1 = 1;
while(1)
{
TL1 = 0x33;
TH1 = 0xEE;
TR1 = 1;
}
}
}

void TIMER1_ISR(void) interrupt 3
{
TF1 = 0;
TR1 = 0;

port = ~ port;
}

Please help me.Is there any mistake in my Code or the Data sheet is wrong.