HC705E5GRSSLASHD datasheet(46/148 Pages) NXP

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Resets

General Release Specification

MC68HC705E5 — Rev. 1.0

Resets

5.6.4 COP Watchdog Timer Considerations

If enabled by a mask option, the COP watchdog timer is active in all

modes of operation (disabled in test and self-check modes). 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) will cause the oscillator to halt and prevent the COP watchdog

timer from timing out. Therefore, it is recommended that the STOP

instruction should be disabled if the COP watchdog timer is enabled.

If the COP watchdog timer is selected by a mask option, the COP will

reset the MCU when it times out. Therefore, it is recommended that the

COP watchdog should be 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 Figure 5-1.

5.7 Illegal Address Reset

When an opcode fetch occurs from an address which is not implemented

in the RAM ($0080–$01FF) or ROM ($0F00–$1FFF), the part is reset

automatically.

Table 5-1. COP Watchdog Timer Recommendations

IF the Following Conditions Exist:

THEN the COP Watchdog

Timer Should Be:

STOP Instruction

Wait Time

Converted to Reset

WAIT Time

Less Than

COP Time-Out

Enable or Disable COP

by Mask Option

Converted to Reset

WAIT Time

More Than

COP Time-Out

Disable COP by Mask Option

Acts as STOP

Any Length

WAIT Time

Disable COP by Mask Option

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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