39.4.1.2 Debug mode
In Debug mode, the timers will be frozen based on MCR[FRZ]. This is intended to aid
software development, allowing the developer to halt the processor, investigate the
current state of the system, for example, the timer values, and then continue the
operation.
39.4.2 Interrupts
All the timers support interrupt generation. See the MCU specification for related vector
addresses and priorities.
Timer interrupts can be enabled by setting TCTRLn[TIE]. TFLGn[TIF] are set to 1 when
a timeout occurs on the associated timer, and are cleared to 0 by writing a 1 to the
corresponding TFLGn[TIF].
39.4.3 Chained timers
When a timer has chain mode enabled, it will only count after the previous timer has
expired. So if timer n-1 has counted down to 0, counter n will decrement the value by
one. This allows to chain some of the timers together to form a longer timer. The first
timer (timer 0) cannot be chained to any other timer.
39.5 Initialization and application information
In the example configuration:
• The PIT clock has a frequency of 50 MHz.
• Timer 1 creates an interrupt every 5.12 ms.
• Timer 3 creates a trigger event every 30 ms.
The PIT module must be activated by writing a 0 to MCR[MDIS].
The 50 MHz clock frequency equates to a clock period of 20 ns. Timer 1 needs to trigger
every 5.12 ms/20 ns = 256,000 cycles and Timer 3 every 30 ms/20 ns = 1,500,000 cycles.
The value for the LDVAL register trigger is calculated as:
LDVAL trigger = (period / clock period) -1
Chapter 39 Periodic Interrupt Timer (PIT)
K22F Sub-Family Reference Manual , Rev. 3, 7/2014
Freescale Semiconductor, Inc.
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