Introduction to manual calculation of timer interrupts

The following software calculates 12M crystal oscillator, timer mode 16 bit in 12T 1 milliseconds time

void Timer0init (void)//1 ms @12.000mhz{auxr &= 0x7f;//Timer clock 12T mode tmod &= 0xf0;//set timer mode tmod |= 0x01;//set Timer mode TL0 = 0x18;//Set Timing initial value TH0 = 0xfc;//Set Timing initial value TF0 = 0;//Clear TF0 Flag TR0 = 1;//Timer 0 start Timer}

Verify the results of the software:

Crystal oscillator 12M, one Oscillation time is (1/12m) seconds

12T microcontroller One machine cycle is 12 clock cycle 0.000001 seconds

12M Crystal oscillator 12T work a machine cycle consumes time is (1/12m) *12 seconds =0.000001 seconds =1 microseconds

Requires a delay of 1 milliseconds, which is 1000 microseconds

Low 8-bit and high 8 for a total of 16-bit 65535, can only be installed in 65535 microseconds time

thx= (65536-1000)/256=252=0XFC

tlx= (65536-1000)%256 =18=0x18

"Manual calculation" with 11.0592M delay 20 ms

20 milliseconds = 0.02 seconds

One machine cycle time (12/(11.0592*10^6)) seconds

0.02-second Cycle =0.02/(12/(11.0592*10^6)) = 18,432 Machine Cycles

11.0592M 12T 1-bit 20 ms

th0= (65536-18432)/256=0xb8

th0= (65536-18432)%256=0x00

Software to verify my calculations:

void Timer0init (void)//20 ms @11.0592mhz{auxr &= 0x7f;//Timer clock 12T mode tmod &= 0xf0;//set timer mode tmod |= 0x01;// Set Timer mode TL0 = 0x00;//Set Timing initial value TH0 = 0xb8;//Set Timing initial value TF0 = 0;//Clear TF0 Flag TR0 = 1;//Timer 0 start Timer}

The EA---allow bits in the global.

Ea=1, the global interrupt control is turned on, in which case the individual interrupt control bits determine the opening or closing of the corresponding interrupt.

Ea=0, turn off all interrupts.

ET2---Timer/Counter 2 interrupt allow bit.

Et2=1, open T2 interrupt.

Et2=0, close the T2 interrupt.

ES---Serial port interrupt allow bit.

Es=1, open the serial port interrupt.

Es=0, turn off the serial port interrupt.

ET1---Timer/counter 1 interrupt allow bit.

Et1=1, open T1 interrupt.

Et1=0, close the T1 interrupt.

EX1---External interrupt 1 interrupt allow bit.

Ex1=1, open an external interrupt 1 interrupt.

Ex1=0, close the external interrupt 1 interrupt.

ET0---Timer/Counter 0 interrupt allow bit.

Et0=1, open T0 interrupt.

Et0=0, close the T0 interrupt.

EX0---External interrupt 0 interrupt allow bit.

Ex0=1, open an external interrupt 0 interrupt.

Ex0=0, close the external interrupt 0 interrupt.

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Introduction to manual calculation of timer interrupts