I ms delay creating in 8051

[thannara123]

making one milli second delay in 8051 using timer mode is the following programme is correct ?
crystal frequency is 20MHz

#include <REGX51.H>void _ms_delay(unsigned int delay)
{
		while(delay != 0)  // mult delay 
		{	--delay;
            TMOD = 0x01;                            // Timer1 mode0


            TH0= 0xF9;                               //initial value for 1ms


            TL0 = 0x7D;


            TR0 = 1;                                       // timer start


            while (TF0 == 0);                     // check overflow condition


            TR0 = 0;                                      // Stop Timer


            TF0 = 0;                                      // Clear flag


}  }




void main()


{


_ms_delay(2); // calling two milli second




}

 

[slutarius]

Too long time for me to recall this uC, but I did calculate all hardware clock cycle needed in that loop, then mulitiply with clock period to get delay time.
You should know how much clock cycles that your loop would take firstly.

 

[KlausST]

Hi,

Using timer...

One thing is obvious: you have a 20MHz clock andneed to delay for 1ms.

20MHz x 1ms = 20000 clock ticks.

I can't find any information in yourcode how you want to achieve this.
(But I only had a quick view...I'm not familiar with 8051s and their periferals).

Maybe some comments or additional information could help.

Klaus

 

[slutarius]

On goolge I found some link would be helpful:

https://what-when-how.com/8051-microcontroller/time-delay-for-various-8051-chips/
https://what-when-how.com/8051-microcontroller/programming-timers-0-and-1-in-8051-c/

Both C and Assembly.

 

[paulfjujo]

hello

Q=20Mhz MC=0,60µS
if 8051 timer is similar to PIC timer
you need to spend 1666 * 0,6 => 1 mS
load the timer with 65535-1666=63869 ..
TH0= 0xF9; //initial value for 1ms
TL0 = 0x7D;
0xF97D => 63869
so seems to be OK if timer has no prescaler or potsscaler
and use MC as clock.