MPC5604B/C Microcontroller Reference Manual, Rev. 8
Freescale Semiconductor 251
13.7 API functional description
Setting the RTCC[APIEN] bit enables the autonomous interrupt function. The 10-bit RTCC[APIVAL]
field selects the time interval for triggering an interrupt and/or wakeup event. Since the RTC is a free
running counter, the APIVAL is added to the current count to calculate an offset. When the counter reaches
the offset count, a interrupt and/or wakeup request is generated. Then the offset value is recalculated and
again re-triggers a new request when the new value is reached. APIVAL may only be updated when APIEN
is disabled. When a compare is reached, the RTCS[APIF] interrupt flag bit is set (after proper clock
synchronization). If the RTCC[APIIE] interrupt enable bit is set, then the API interrupt request is
generated. If there is a match while in low power mode, then the API will first generate a wakeup request
to force a wakeup into normal operation, then the APIF flag will be set.
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