MC68HC705P9CDW FREESCALE [Freescale Semiconductor, Inc], MC68HC705P9CDW Datasheet - Page 96

• Manufacturer Part Number: MC68HC705P9CDW
• Description: Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Computer Operating Properly Watchdog (COP)
8.3 Introduction
8.4 Operation
8.4.1 COP Watchdog Timeout
8.4.2 COP Watchdog Timeout Period
Technical Data
96
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 programmable in the
mask option register.
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
Resets and
Use the following formula to calculate the COP timeout period:
where
Freescale Semiconductor, Inc.
Computer Operating Properly Watchdog (COP)
For More Information On This Product,
Go to: www.freescale.com
Interrupts.
COP timeout period
f
BUS
=
crystal frequency
-------------------------------------------- -
=
2
131 072 cycles
-------------------------------------- -
,
f
BUS
MC68HC705P9 — Rev. 4.0
Section 5.
MOTOROLA