PXR40RM Datasheet, PDF (520/1434 Pages) Freescale Semiconductor, Inc – PXR40 Microcontroller

Periodic Interrupt Timer (PIT_RTI)
The counter period can be restarted, by first disabling, then enabling the timer with the TEN bit (see
Figure 20-7).
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 Figure 20-8). In the case of the RTI, because of the different clock
domains (system clock / oscillator clock), a delay must be respected between setting the new value and
re-enabling the RTI.
It is also possible to change the counter period without restarting the timer by writing the LDVAL register
with the new load value. This value is loaded after the next trigger (counter reaches 0) event (see
Figure 20-9).
Timer Enabled
Start Value = p1
Disable
Timer
Re-Enable
Timer
Trigger
Event
p1
p1
p1
p1
Figure 20-7. Stopping and Starting a Timer
Timer Enabled
Start Value = p1
Trigger
Event
Disable
Timer,
Set new
Re-Enable
Timer
Load Value
p2
p2
p2
p1
p1
Figure 20-8. Modifying Running Timer Period
Timer Enabled
Start Value = p1
New Start
Value p2 set
Trigger
Event
p1
p1
p1
p2
p2
Figure 20-9. Dynamically Setting a New Load Value
20.4.1.2 Debug Mode
In debug mode the timers may be configured to stop when the debugger halts the device. This is intended
to aid software development, allowing the developer to halt the processor, investigate the current state of
the system (e.g. the timer values) and then continue the operation.
20-8
PXR40 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor