at91cap7e ATMEL Corporation, at91cap7e Datasheet - Page 86

• Manufacturer Part Number: at91cap7e
• Description: Customizable Microcontroller
• Manufacturer: ATMEL Corporation

Figure 16-2. Enabling/Disabling PIT with PITEN
86
MCK Prescaler
PITS (PIT_SR)
APB Interface
AT91CAP7E
PITEN
PICNT
CPIV
15
0
0
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 exam-
ple, 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 register (disabled on
reset). The PITEN bit only becomes effective when the CPIV value is 0.
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.
1
0
PIV - 1
PIV
MCK
read PIT_PIVR
1
APB cycle
0
APB cycle
0
restarts MCK Prescaler
Figure 16-2
1
8549A–CAP–10/08
illustrates