Test: Timer Programming

Timer’s clock source is the crystal that is applied to the controller.

The frequency of the clock source for the timer is equal to f/12( where f is frequency of the crystal ).

TMOD register is used to set different timer’s or counter’s to their appropriate modes so that it tells the user that what mode is being used when operating any timer or counter.

For generating the maximum delay we have to multiply the maximum number of counts with the time period required to execute one machine cycle( 65536*1/22MHz).

Auto reload is allowed in the Mode 2 of the timer because here in this mode, we don’t need to load the count again and again in the register.

For Mode 0 13 bit value is used so 1FFFH is chosen to be the roll over value. Similarly for Mode 1 FFFFH and for Mode 2 FFH is the roll over value for the timers and counter.

When any timer is to turn on, then firstly we have to load the TMOD register and the count. Then timer is to get started. After then, we need to monitor the timer properly and then when the roll over condition arises then timer is to be stopped.

If Timer 0 is to be used as a counter, then a pulse has to be applied at P3.4 and if it is for Timer 1 then the clock pulse has to be applied at the pin P3.5.

Hex value that is being loaded in the TH1 register is the two’s complement of the value being loaded in it.

These bits are of TCON register. It tells us about the overflow flag bit and the run control bit