General Operation - NXP Semiconductors MKL27Z128VFM4 Reference Manual

Table of Contents

30.5.1 General operation

This section gives detailed information on the internal operation of the module. Each

timer can be used to generate trigger pulses and interrupts. Each interrupt is available on

a separate interrupt line.

30.5.1.1 Timers

The timers generate triggers at periodic intervals, when enabled. The timers load the start

values as specified in their LDVAL registers, count down to 0 and then load the

respective start value again. Each time a timer reaches 0, it will generate a trigger pulse

and set the interrupt flag.

All interrupts can be enabled or masked by setting TCTRLn[TIE]. A new interrupt can be

generated only after the previous one is cleared.

If desired, the current counter value of the timer can be read via the CVAL registers.

The counter period can be restarted, by first disabling, and then enabling the timer with

TCTRLn[TEN]. See the following figure.

Timer enabled

Start value = p1

The counter period of a running timer can be modified, by first disabling the timer,

setting a new load value, and then enabling the timer again. See the following figure.

Timer enabled

Start value = p1

It is also possible to change the counter period without restarting the timer by writing

LDVAL with the new load value. This value will then be loaded after the next trigger

event. See the following figure.

Freescale Semiconductor, Inc.

Figure 30-2. Stopping and starting a timer

Disable timer,

Set new load value

Figure 30-3. Modifying running timer period

KL27 Sub-Family Reference Manual , Rev. 5, 01/2016

Chapter 30 Periodic Interrupt Timer (PIT)