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Hi, i want to tune my timer ISR to 20hz , 1/20 sec , i dont know what are the values to be loaded with the timer.
void timer0_isr (void) interrupt 1 using 1 { unsigned i; TR0 = 0; /* stop timer 0 */ TL0 = ; TH0 = ; TR0 = 1; overflow_count++; }
reload value will derpendd on clock frequenccy
also timer mode
what frequeency you be crystal use amd timer mode???????
you give info i help good
i am profesional and know x51 well
thanks for your reply , im using the usua 11.49 Mhz ,timer mode 16 bit with reload
50ms at 11.49MHz
50e-3/ (1 / ((11.49 * 1e6) / 12)) = 47875
Reload value = 65536 - 47875 = 17661
Reload HI = 17661 / 256 = 0x44 = 68 Reload LO = 17661 % 256 = 0xFD = 253
thanks i got the idea is this correct to make ISR at 15ms ~ 15hz ?
static unsigned long overflow_count = 0; void timer1_ISR (void) interrupt 3 { overflow_count++; /* Increment the overflow count */ } /*------------------------------------------------ MAIN C function ------------------------------------------------*/ void main (void) { Set the Timer1 Run control bit. --------------------------------------*/ TMOD &= 0xF0; // Clear all T0 bits (T1 left unchanged) TMOD |= 0x01; TH1 = 0xC5; TL1 = 0x68; ET1 = 1; /* Enable Timer 1 Interrupts */ TR1 = 1; /* Start Timer 1 Running */ EA = 1; /* Global Interrupt while (1) { } }