Information

System Configuration
MPC8308 PowerQUICC II Pro Processor Reference Manual, Rev. 1
Freescale Semiconductor 5-47
— RTC uses the internal input clock mode (RTCNR[CLIN] = 0)
— RTC uses the external RTC_PIT_CLOCK (RTCNR[CLIN] = 1)
5.4.8 RTC Reset Sequence
The RTC is not reset automatically on POR or HRESET.
• To assert reset to the RTC, program RTCCR[RESET_RTC] to 1.
• To deassert reset to the RTC, program RTCCR[RESET_RTC] to 0.
5.4.9 RTC Initialization Sequence
The recommended initialization sequence for the RTC is as follows:
1. Write to RTPSR to set the RTC prescaler to the desired value
2. Write to RTLDR to initialize the RTC initial value
3. Write to RTALR to program the RTC alarm value, if needed
4. Write to RTCNR to configure and start the RTC operation: RTC input clock source, second/alarm
interrupt mask, and RTC clock enable
5.5 Periodic Interval Timer (PIT)
The following sections describe theory of operation of the periodic interval timer (PIT) including a
definition of the external signals and the functions it serves. Additionally, the configuration, control, and
status registers are described. Note that individual chapters in this reference manual describe additional
specific initialization aspects for each individual block.
5.5.1 PIT Overview
The periodic interval timer (PIT) that generates periodic interrupts for a real-time operating system or an
application software.
The PIT consists of a 32-bit down-counter which is decremented by a clock derived from a CSB clock or
from an external 32.768-kHz crystal. The 32-bit counter decrements to zero when loaded with an initial
value from the periodic interval timer load register (PTLDR). The periodic interval timer control register
(PTCTR) is used to enable or disable the various timer functions. The periodic interval timer event register
(PTEVR) is used to report the interrupt source. The PIT function can be disabled if needed.