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Periodic Interrupt Timer (PIT)
MPC5644A Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor
1631
34.5
Functional description
34.5.1
General
This section gives detailed information on the internal operation of the module. Each timer can be used to
generate trigger pulses as well as to generate interrupts, each interrupt will be available on a separate
interrupt line. Additionally the RTI timer can be used to wakeup the processor.
34.5.1.1
Timers / RTI
The timers generate triggers at periodic intervals, when enabled. They load their start values, as specified
in their LDVAL registers, then count down until they reach 0. Then they load their 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 the TIE bits in the TCTRL registers). A new interrupt
can be generated only after the previous one is cleared. Since in the case of the RTI, clearing the interrupt
crosses clock domains, a minimum load value of 32 should be maintained.
If desired, the current counter value of the timer can be read via the CVAL registers. The value of the RTI
counter can be delayed considerably, as it is synchronized to the bus clock from the RTI clock domain.
The counter period can be restarted, by first disabling, then enabling the timer with the TEN bit (see
).
Offset channe 0x0C
Access: Read/Write
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
R
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
R
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
TIF
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Figure 34-6. Timer Flag Register (TFLG)
Table 34-7. TFLG field descriptions
Field
Description
TIF
Time Interrupt Flag
TIF is set to 1 at the end of the timer period.This flag can be cleared only by writing it with a 1. Writing
a 0 has no effect. If enabled (TIE = 1), TIF causes an interrupt request.
0: Timeout has not yet occurred
1: Timeout has occurred
Summary of Contents for MPC5644A
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