Lowest square wave frequency that we can generate using mode 1 and mode 2 At XLAT=16MHZ

2KHZ Frequency Wave Generation Programme:


#include<reg51.h>
sbit OUTPUT=P1^7;
void delay()
{
    unsigned int i;
    TMOD=TMOD & 0xF0;
    TMOD=TMOD | 0x01;
    TH0=0xFD;
    TL0=0x66;
    TR0=1;
    while(TF0==0);
    TR1=0;
}
void main()
{
    while(1)
    {
        OUTPUT=1;
        delay();
        OUTPUT=0;
    }
}

Lowest Frequency Generation Explanation:

 Lowest Square Wave Frequency Means Highest Time Delay.

 Here Our Crystal Or Oscillator Frequency Is 20KHZ.
 So Our CP=12/16KHZ=0.75 micro
 To Get Maximum Time Delay We Must Have Value Of THX-TLX is 0(zero).

For Mode 1:
    Mode 1 is 16bit-Timer.
    When We Take Initial Value as a 2^16 Than THX-TLX become 0(zero).
    so Initial Value= 2 ^ 16 = 65536
    And We Know CP=0.6 micro
    So TIME= CP * Initial Value
           = 0.75 * 10^-6 * 65536
           = 49152 microsecond
    Now Frequency=1/TIME
                 =1/(49152 * 10^-6)
                 =20.3450 HZ

For Mode 2:
    Mode 1 is 8bit-Timer.
    When We Take Initial Value as a 2^16 Than THX-TLX become 0(zero).
    so Initial Value= 2 ^ 8 = 256
    And We Know CP=0.6 micro
    So TIME= CP * Initial Value
           = 0.75 * 10^-6 * 256
           = 192 microsecond
    Now Frequency=1/TIME
                 =1/(192 * 10^-6)
                 =5.2083 KHZ