CHAPTER 6 WATCHDOG TIMER

6.4Operations of Watchdog Timer Functions

The watchdog timer generates a watchdog reset when the watchdog timer counter overflows.

■Operations of Watchdog Timer

●Activating watchdog timer

The watchdog timer is activated when the first time "0101B" is written to the watchdog control bits (WDTC: WTE3 to WTE0) of the watchdog control register.

The watchdog timer cannot be stopped without accepting a reset upon activation.

●Clearing watchdog timer

The watchdog timer counter is cleared the second or subsequent time "0101B" is written to the watchdog control bits (WDTC: WTE3 to WTE0) of the watchdog control register.

When the counter is not cleared within the time interval of the watchdog timer, the counter overflows and the timer generates the internal reset signal having a period of four instruction cycles.

●Time intervals of watchdog timer

The time interval varies depending on the timing at which the watchdog timer is cleared. Figure 6.4-1shows the relationship between the clear timings and time intervals of the watchdog timer when output from the time-base timer is used as the count clock (oscillation frequency: 12.5 MHz).

Figure 6.4-1 Clearing Watchdog Timer and Time Interval

Minimum time interval

335.5 ms

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Count clock output from

 

 

 

 

 

 

 

 

time-base timer

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Overflow

 

 

Watchdog clear

 

 

 

Watchdog 1-bit counter

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Watchdog reset

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Maximum time interval

671.0 ms

Count clock output from time-base timer

Watchdog clear

Overflow

Watchdog 1-bit counter

Watchdog reset

131

Page 146 Page 148
Page 147
Image 147
Fujitsu F202RA, MB89202 manual Operations of Watchdog Timer Functions, Activating watchdog timer, Clearing watchdog timer
Page 146 Page 148

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.
Top Page Image Contents