Resets

Internal 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 a mask option and is verified during production testing.

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.

MC68HC05RC16 — Rev. 3.0

 

General Release Specification

 

 

 

MOTOROLA

Resets

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