HC705E5GRSSLASHD datasheet(45/148 Pages) NXP

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Resets

Computer Operating Properly Reset (COPR)

MC68HC705E5 — Rev. 1.0

General Release Specification

Resets

5.6 Computer Operating Properly Reset (COPR)

The MCU contains a watchdog timer that automatically times out if not

reset (cleared) within a specific time by a program reset sequence. If the

COP watchdog timer is allowed to timeout, an internal reset is generated

to reset the MCU. Regardless of an internal or external reset, the MCU

comes out of a COP reset according to the standard rules of mode

selection.

The COP reset function is enabled or disabled by a mask option and is

verified during production testing.

The COP watchdog reset will activate the internal pulldown device

connected to the RESET pin.

5.6.1 Resetting the COP

Preventing a COP reset is done by writing a logic 0 to the COPF bit. This

action will reset the counter and begin the timeout period again. The

COPF bit is bit 0 of address $1FF0. A read of address $1FF0 will return

user data programmed at that location.

5.6.2 COP During Wait Mode

The COP will continue to operate normally during wait mode. The

software should pull the device out of wait mode periodically and reset

the COP by writing to the COPF bit to prevent a COP reset.

5.6.3 COP During Stop Mode

When the stop enable mask option is selected, stop mode disables the

oscillator circuit and thereby turns the clock off for the entire device. The

COP counter will be reset when stop mode is entered. If a reset is used

to exit stop mode, the COP counter will be held in reset during the 4064

cycles of startup delay. If any operable interrupt is used to exit stop

mode, the COP counter will not be reset during the 4064-cycle startup

delay and will have that many cycles already counted when control is

returned to the program.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

HC705E5GRS/D Datasheet(PDF) 45 Page - NXP Semiconductors