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5.5.2.4 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 intentionally or inadvertently due to the CPU being disturbed) causes the oscillator to halt and prevents 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 be disabled for a system that must have intentional uses of the wait mode for periods longer than the COP time out period.

The recommended interactions and considerations for the COP watchdog timer, STOP instruction, and WAIT instruction are summarized in Table 5-1.

Table 5-1. COP Watchdog Timer Recommendations

IF the Following Conditions Exist:

THEN the COP Watchdog Timer

 

Wait Time

Should Be as Follows:

 

 

 

Wait Time Less than COP Time-Out

Enable or Disable COP by Mask Option

 

 

Wait Time More than COP Time-Out

Disable COP by Mask Option

 

 

Any Length Wait Time

Disable COP by Mask Option

 

 

General Release Specification

 

MC68HC05RC16 — Rev. 3.0

 

 

 

50

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