MC68HC05BD3 Datasheet, PDF (88/112 Pages) Motorola, Inc – HCMOS microcontroller

10.3
COP Watchdog Timer Considerations
The COP watchdog timer is always enabled in MC68HC05BD3. It will reset the MCU when it times
out. For a system that must have intentional uses of the WAIT Mode, care must be taken to prevent
such situations from happening during normal operations by arranging timely interrupts to reset
the COP watchdog timer.
WAIT
External oscillator active
and
Internal Timer Clock Active
Stop internal processor clock,
Clear I bit in CCR
10
MOTOROLA
10-2
External
Y
reset?
N
Internal COP ^Y
reset?
N
External H/W ^Y
reset?
N
Internal
Y
interrupt?
N
Restart internal
processor clock
1. Fetch reset vector
or
2. Service interrupt
a. Stack
b. Set I bit
c. Vector to interrupt routine
Figure 10-1 WAIT Flowchart
LOW POWER MODES
TPG
MC68HC05BD3