Features - Freescale Semiconductor MCF5329 Reference Manual

Real-Time Clock
25.1.2

Features

The RTC module includes:
• Full clock—days, hours, minutes, seconds
• Minute countdown timer with interrupt
• Programmable daily alarm with interrupt
• Sampling timer with interrupt
• Once-per-day, once-per-hour, once-per-minute, and once-per-second interrupts
• Operation at 32.768 kHz, 32 kHz, or 38.4 kHz (determined by reference clock crystal)
25.1.3 Modes of Operation
The real-time-clock operates in various modes as described below:
• Time-of-day counters
— The prescaler divides the reference clock down to 1 Hz. The reference frequencies of
32.768 kHz, 38.4 kHz and 32 kHz are supported.
— The 1 Hz clock increments four counters that are located in three registers
– RTC_SECONDS contains the 6-bit seconds counter
– RTC_HOURMIN contains the 6-bit minutes counter and 5-bit hours counter
– RTC_DAYS contains the 16-bit day counter
• Alarm
— There are three alarm registers that mirror the three counter registers. An alarm is set by
accessing the real-time clock alarm registers (RTC_ALRM_SEC, RTC_ALRM_HM, and
RTC_ALRM_DAY) and loading the exact time that the alarm should generate an interrupt.
When the TOD clock value and the alarm value coincide, an interrupt occurs.
• Sampling Timer
— The prescaler divides the reference clock down to 512 Hz. The sampling timer generates a
periodic interrupt with frequencies specified by the RTC_IER[SAMn,2HZ] bits. This timer can
be used for digitizer sampling, keyboard debouncing, or communication polling.
lists the interrupt frequencies of the sampling timer for the possible reference clocks.
• Minute Stopwatch
— The minute stopwatch performs a countdown with a one minute resolution. It generates an
interrupt on a minute boundary.
25-2
MCF5329 Reference Manual, Rev 3
Table 25-13
Freescale Semiconductor