Datasheet

109
SAM9261 [DATASHEET]
Atmel-6062O-ATARM-SAM9261-Datasheet_21-Jun-16
When CPIV and PICNT values are obtained by reading the Periodic Interval Value Register (PIT_PIVR), the
overflow counter (PICNT) is reset and the PITS is cleared, thus acknowledging the interrupt. The value of PICNT
gives the number of periodic intervals elapsed since the last read of PIT_PIVR.
When CPIV and PICNT values are obtained by reading the Periodic Interval Image Register (PIT_PIIR), there is
no effect on the counters CPIV and PICNT, nor on the bit PITS. For example, a profiler can read PIT_PIIR without
clearing any pending interrupt, whereas a timer interrupt clears the interrupt by reading PIT_PIVR.
The PIT may be enabled/disabled using the PITEN bit in the PIT_MR (disabled on reset). The PITEN bit only
becomes effective when the CPIV value is 0. Figure 15-2 illustrates the PIT counting. After the PIT Enable bit is
reset (PITEN= 0), the CPIV goes on counting until the PIV value is reached, and is then reset. PIT restarts
counting, only if the PITEN is set again.
The PIT is stopped when the core enters debug state.
Figure 15-2. Enabling/Disabling PIT with PITEN
MCK Prescaler
PIVPIV - 10
PITEN
10
0
15
CPIV
1
restarts MCK Prescaler
0
1
APB cycle
read PIT_PIVR
0
PICNT
PITS (PIT_SR)
MCK
APB Interface
APB cycle