Freescale Semiconductor, Inc.
Clock Functions
Real-Time Interrupt
In addition, windowed COP operation can be selected. In this mode,
writes to the COPRST register must occur in the last 25% of the selected
period. A premature write will also reset the part.
12.10 Real-Time Interrupt
There is a real time (periodic) interrupt available to the user. This
interrupt will occur at one of seven selected rates. An interrupt flag and
an interrupt enable bit are associated with this function. There are three
bits for the rate select.
12.11 Clock Monitor
The clock monitor circuit is based on an internal resistor-capacitor (RC)
time delay. If no EXTALi clock edges are detected within this RC time
delay, the clock monitor can optionally generate a system reset. The
clock monitor function is enabled/disabled by the CME control bit in the
COPCTL register. This time-out is based on an RC delay so that the
clock monitor can operate without any EXTALi clock.
Clock monitor time-outs are shown in Table 12-3. The corresponding
EXTALi clock period with an ideal 50% duty cycle is twice this time-out
value.
Table 12-3. Clock Monitor Time-Outs
Supply
Range
5 V +/– 10%
2–20 µS
68HC(9)12D60 — Rev 4.0
MOTOROLA
Advance Information
173
Clock Functions
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