HC705RC16GRSSLASHD datasheet(47/120 Pages) NXP

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Resets

Internal Resets

MC68HC705RC16 — Rev. 3.0

General Release Specification

Resets

5.5.2 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 time out, an internal reset is

generated to reset the MCU.

The COP reset function is enabled or disabled by the mask option

registers (MOR).

5.5.2.1 Resetting the COP

Writing a zero to the COPF bit prevents a COP reset. This action resets

the counter and begins the time-out period again. The COPF bit is bit 0

of address $3FF0. A read of address $3FF0 returns user data

programmed at that location.

5.5.2.2 COP During Wait Mode

The COP continues 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.

5.5.2.3 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.

When stop is executed, the COP counter will hold its current state. If a

reset is used to exit stop mode, the COP counter is reset and held until

4064 POR cycles are completed. At this time, counting will begin. If an

external IRQ is used to exit stop mode, the COP counter does not wait

for the completion of the 4064 POR cycles but does count these cycles.

It is, therefore, recommended that the COP is fed before executing the

STOP instruction.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

HC705RC16GRS/D Datasheet(PDF) 47 Page - NXP Semiconductors