MC68HC05P9ACDW FREESCALE [Freescale Semiconductor, Inc], MC68HC05P9ACDW Datasheet - Page 80

• Manufacturer Part Number: MC68HC05P9ACDW
• Description: HCMOS Microcontroller Unit
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

COP
Introduction
Operation
COP Watchdog
Timeout
COP Watchdog
Timeout Period
80
NOTE:
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.
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.
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
and Interrupts
Use the following formula to calculate the COP timeout period:
where
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COP Timeout Period
section.
COP
f
BUS
=
crystal frequency
-------------------------------------------- -
=
2
131 072 cycles
-------------------------------------- -
,
f
BUS
MOTOROLA
Resets
6-cop0cop