Discussion in "8051 Discussion Forum" started by    wounder    Jan 25, 2020.
Sat Jan 25 2020, 05:44 pm
#1
I have a 8051 micro controller ,it has timer0,1,2,3 with different modes.

in timer0,mode0, i got a sample code (as shown below).

from that code

TH0_INIT=0xFC //[email protected]=12MHz, Period = (10.85/2) [email protected]=22.1184MHz TL0_INIT=0x0F

both TH0,TL0 load with hex values..but could not derive these values from equation below .. (https://exploreembedded.com/wiki/5.8051_Timer_programming) Could you please tell me ,how these hex values derive ??

tick = (1/(Fosc/12)

tick = 12/Fosc$$ For Fosc == 11.0592Mhz, the tick time will be

tick = 12/11.0592M = 1.085069444us = 1.085us

Now the Timer value for the required delay can be calculated as below.

Delay = TimerCount * tick

Count = (Delay/tick)

RegValue = TimerMax- Count RegValue = TimerMax-(Delay/tick) = TimerMax - (Delay/1.085us)

RegValue = TimerMax-((Delay/1.085) * 10^6)$$


#include "SFR_Macro.h"
#include "Function_define.h"

#define TH0_INIT 0xFC //[email protected]=12MHz, Period = (10.85/2)
[email protected]=22.1184MHz
#define TL0_INIT 0x0F


void Timer0_ISR (void) interrupt 1 //interrupt address is 0x000B
{
TH0 = TH0_INIT;
TL0 = TL0_INIT;
P12 = ~P12; // GPIO
toggle when interrupt
}



void main (void)
{
TMOD = 0XFF;
Set_All_GPIO_Quasi_Mode;
TIMER0_MODE0_ENABLE;


clr_T0M;
clr_T1M;

TH0 = TH0_INIT;
TL0 = TL0_INIT;


// set_ET0; //enable Timer0 interrupt
//enable Timer1 interrupt
set_EA; //enable interrupts

set_TR0; //Timer0 run


while(1)
{
TH0 = TH0_INIT;
TL0 = TL0_INIT;
set_TR0;
while(!TF0);
clr_TR0;
P12 = ~P12;
TF0 = 0 ;
}
}
Sun Jan 26 2020, 09:35 am
#2
For a 12MHz crystal using a normal divided by 12 clock.

For a 5mS delay I get
TH0_INIT=0xEC
TL0_INIT=0x78
What do you get ?

The program you posted uses polling and an interrupt to monitor the timer
and toggle P12, choose one, you can't (at least shouldn't) do both.

Get Social

Information

Powered by e107 Forum System

Downloads

Comments

ThomasExile
Sat Apr 01 2023, 08:52 am
trowext
Fri Mar 31 2023, 02:24 pm
gok
Fri Mar 31 2023, 01:32 pm
PlamenaStoli
Thu Mar 30 2023, 01:21 pm
KennethAlodo
Thu Mar 30 2023, 07:38 am
Michailwgn
Thu Mar 30 2023, 01:23 am
KennethGluct
Wed Mar 29 2023, 06:34 pm
adorkPam
Wed Mar 29 2023, 05:56 pm