HC705CT4GRSSLASHD datasheet(47/152 Pages) NXP

47 / 152 page

Resets

Internal Resets

MC68HC705CT4 — Rev. 2.0

General Release Specification

MOTOROLA

Resets

of address $1FF0. A read of address $1FF0 returns user data

programmed at that location.

5.4.2.2 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.

5.4.2.3 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 that 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 it does count these

cycles. It is recommended, therefore, that the COP is fed before

executing the STOP instruction.

5.4.2.4 COP Watchdog Timer Considerations

The COP watchdog timer is active in all modes of operation if enabled

by a mask option. If the COP watchdog timer is selected by a mask

option, any execution of the STOP instruction (either intentional or

inadvertent due to the CPU being disturbed) causes the oscillator to halt

and prevent the COP watchdog timer from timing out. If the COP

watchdog timer is selected by a mask option, the COP resets the MCU

when it times out. Therefore, it is recommended that the COP watchdog

is disabled for a system that must have intentional uses of the wait

mode for periods longer than the COP timeout period.

The recommended interactions and considerations for the COP

watchdog timer, STOP instruction, and WAIT instruction are

summarized in Table 5-1.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

HC705CT4GRS/D 데이터시트(PDF) 47 Page - NXP Semiconductors