MC68HC05P9A Datasheet, PDF (80/158 Pages) Freescale Semiconductor, Inc – HCMOS Microcontroller Unit

COP
Introduction
Operation
Freescale Semiconductor, Inc.
The purpose of the computer operating properly (COP) watchdog is to
reset the MCU in case of software failure. Software that is operating
properly periodically services the COP watchdog and prevents the reset
from occurring. The COP watchdog function is selectable with a mask
option.
COP Watchdog
Timeout
The COP watchdog is a 16-bit counter that generates a reset if allowed
to time out. Periodically clearing the counter starts a new timeout period
and prevents the COP from resetting the MCU. A COP watchdog
timeout indicates that the software is not executing instructions in the
correct sequence.
NOTE:
The internal clock drives the COP watchdog. Therefore, the COP
watchdog cannot generate a reset for errors that cause the internal clock
to stop.
The COP watchdog also depends on a power supply voltage at or above
a minimum specification and is not guaranteed to protect against
brownout. For information about brownout protection, see the Resets
and Interrupts section.
COP Watchdog
Timeout Period
Use the following formula to calculate the COP timeout period:
where
COP Timeout Period = -1---3---1----,-0--f--7-_B--2_U---_S---c---y---c---l-e---s
f_BUS = ^c---^r--^y---^s---^t--^a---^l---^f--^r2--^e---^q---^u----^e---ⁿ---^c---^y--
6-cop0cop
80
COP
MOTOROLA
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