CHAPTER 6 WATCHDOG TIMER

6.1Overview of Watchdog Timer

The watchdog timer is a 1-bit counter that uses output from the time-base timer, based on oscillation frequency, as the count clock. The watchdog timer resets the CPU when not cleared within a specified period after activation.

■Watchdog Timer Function

The watchdog timer is a counter for preventing programs from hanging up. The timer must be cleared at specified intervals after being activated. If the timer is not cleared within a specified period of time because, for example, a program goes into an endless loop, the timer sends to the CPU a watchdog reset having a period of four instruction cycles.

The watchdog timer uses the output from the time-base timer as the count clock.

The time intervals for the watchdog timer are listed in Table 6.1-1 . When the watchdog timer is not cleared, a watchdog reset occurs following the time between the minimum time interval and the maximum time interval. The counter must be cleared before the time of the minimum time interval.

Table 6.1-1 Watchdog Timer Time Intervals

 

Count clock

 

 

 

Time-base timer output (Oscillation frequency: 12.5 MHz)

 

 

Minimum time interval

Approximately 335.5 ms *

 

 

Maximum time interval

Approximately 671.0 ms

 

 

*: (number of counts of time-base timer (222)) ⋅ (oscillation frequency (FCH) divided by 2)

See Section "6.4 Operations of Watchdog Timer Functions " for details on the maximum and minimum

time intervals of the watchdog timer.

Notes:

•The watchdog timer counter is cleared when the time-base counter is cleared (TBTC : TBR = 0) while output from the time-base timer is selected. Therefore, if the time-base timer counter supplying the count clock is cleared repeatedly within the time interval of the watchdog timer, the watchdog timer does not function correctly.

•When switching to sleep or stop mode, the watchdog timer counter is cleared and stops operating until returning to normal operation (RUN state).

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Fujitsu MB89202, F202RA manual Overview of Watchdog Timer, Watchdog Timer Time Intervals, Count clock
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F202RA, MB89202 specifications

The Fujitsu MB89202 and F202RA microcontrollers are part of the 16-bit microcontroller family, renowned for their robust performance and versatility in a variety of embedded system applications. These devices are tailored for high-efficiency operation across diverse industries, including automotive, consumer electronics, and industrial automation.

One of the main features of the MB89202 is its powerful CPU core, which operates at a clock speed of up to 20 MHz. This enables the microcontroller to perform complex calculations and consumer-grade applications seamlessly. The architecture is designed to handle multiple tasks effectively, making it suitable for real-time operations.

Memory capacity is a vital characteristic of the MB89202, featuring on-chip RAM and ROM configurations. The microcontroller can accommodate different memory variants, providing developers with flexibility in memory allocation based on their application requirements. This adaptability facilitates applications ranging from simple control systems to complex data processing tasks.

The F202RA variant extends the capabilities of the MB89202 by integrating advanced peripheral functions. It includes built-in timers, A/D converters, and serial communication interfaces, which are essential for interfacing with other hardware components or sensors. The availability of these peripherals reduces the need for additional external circuits, thus contributing to a more compact and cost-effective design.

In terms of power management, the MB89202 series employs advanced power-saving technologies. The microcontroller offers various low-power modes, enabling devices to conserve energy during idle times, making it highly suitable for battery-operated applications. This characteristic not only enhances the efficiency of devices but also extends their operational lifespan.

Moreover, the Fujitsu MB89202 series incorporates robust protection features, including watchdog timers and failure detection mechanisms. These safety features ensure reliable operation in critical systems, making them a preferred choice in applications where failure is not an option.

The MB89202 and F202RA microcontrollers also support a range of development tools and environments, including integrated development environments (IDEs) and software libraries, which facilitate rapid application development. With these tools, developers can efficiently prototype, debug, and optimize their applications.

In summary, the Fujitsu MB89202 and F202RA microcontrollers stand out with their efficient performance, extensive memory options, integrated peripherals, and power-saving capabilities, making them ideal for a wide array of embedded applications. Their reliability and robustness further enhance their attractiveness for designers seeking advanced microcontroller solutions.
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