Datasheet
Chapter 14
Real-time counter (RTC)
14.1 Introduction
The real-time counter (RTC) consists of one 16-bit counter, one 16-bit comparator,
several binary-based and decimal-based prescaler dividers, three clock sources, one
programmable periodic interrupt, and one programmable external toggle pulse output.
This module can be used for time-of-day, calendar or any task scheduling functions. It
can also serve as a cyclic wakeup from low power modes, stop3 and wait without the
need of external components.
14.1.1 RTC clock sources
The RTC module can be clocked from the bus clock, XOSC ΜΆ generally 32.768 kHz, and 1
kHz low-power oscillator.
14.1.2 RTC modes of operation
The low frequency clock sources, 32.678 kHz and 1 kHz RC, are available in all modes
above provided that they are enabled prior to entering stop mode. The 32 kHz XTAL is
available in all but reset.
14.1.3 RTC clock gating
The clock to the RTC can be gated on and off using corresponding clock gating control
bit. This bit is set after any reset, which enables the clock to this module. To conserve
power, this control bit can be cleared to disable the clock to this module when not in use.
MC9S08PA60 Reference Manual, Rev. 1, 9/2012
Freescale Semiconductor, Inc. 393