
Functional Controller Module (FCM)
Module Description
MC68HC(9)08LJ60 — Rev. 1.0
Advance Information
MOTOROLA
Functional Controller Module (FCM)
143
NON-DISCLOSURE
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REQUIRED
8.5 Module Description
The functional controller module is an HC08-compatible module
designed for use in paging applications. It connects to the HC08 internal
bus and communicates to the HC08 CPU by way of the address bus,
data bus, and control signals. The crystal oscillator signal (CGMXCLK)
enters the module and connects to the timebase circuit. The timebase
creates clock signals which feed the real-time clock.
8.5.1 Timebase Submodule
The timebase submodule is designed to create timing signals equivalent
to any binary division of the crystal oscillator frequency. Clock signals
created at frequencies of 1 Hz, 2 Hz, and 4 Hz are fed to the real-time
clock (RTC) submodule. When a frequency of 4 Hz is selected, the
frequency will vary from 5 Hz to 3.3 Hz with an average of 4 Hz. The
timebase circuit also generates a 100-Hz clock signal which is fed to the
RTC to produce a software chronograph function. In addition, two
signals (1 kHz and 2 kHz) are created for use by other MCU modules.
Software selectable options are available to support the use of a
32.000-kHz or 38.400-kHz crystal oscillator. The default option is for
38.400 kHz.
8.5.2 Real-Time Clock Submodule
The RTC module consists of the RTC control register, the chronograph
data register, the hours, minutes, and seconds registers for timekeeping,
and the hours and minutes alarm registers. The real-time clock (RTC)
system will provide a periodic interrupt to the CPU of 1 hour, 1 minute, 1
second, 1 Hz, 2 Hz, or 4 Hz for software timekeeping functions and an
interrupt with 10 Hz resolution which can be used to generate
chronometer functions in software. When a a periodic interrupt of 4 Hz
is selected, the periodic interrupt will vary from 5 Hz to 3.3 Hz with an
average of 4 Hz. The chronograph data register can be cleared using the
CHRC bit in the timebase control register. See Figure 8-4. The timebase
counter can also be cleared by setting the TBCLR in the timebase
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Freescale Semiconductor, Inc.
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