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Winbond Microcontroller W78E0516 Embedded Binary Recovering

In below article we are going to introduce watchdog timer which play an important role in the process of Winbond Microcontroller W78E0516 Embedded Binary Recovering:

As we all know that the Watchdog timer is a free-running timer which can be programmed by the user to serve as a system monitor, a time-base generator or an event timer. It is basically a set of dividers that divide the system clock. The divider output is selectable and determines the time-out interval.

When the time-out occurs a system reset can also be caused if it is enabled. The main use of the Watchdog timer is as a system monitor. This is important in real-time control applications. In case of power glitches or electro- magnetic interference, the processor may begin to execute errant code. If this is left unchecked the entire system may crash.

The watchdog time-out selection will result in different time-out values depending on the clock speed. The Watchdog timer will de disabled on reset. In general, software should restart the Watchdog timer to put it into a known state. The control bits that support the Watchdog timer are discussed below.

Watchdog Timer Control Register

ENW : Enable watch-dog if set.

CLRW: Clear watch-dog timer and prescaler if set. This flag will be cleared automatically

WIDL : If this bit is set, watch-dog is enabled under IDLE mode. If cleared, watch-dog is disabled under IDLE mode. Default is cleared.

PS2, PS1, PS0: Watch-dog prescaler timer select. Prescaler is selected when set PS2~0 as follows:

watchdog timer scheme

The time-out period is obtained using the following equation:

 

OSC

´ 214 ´PRESCALER ´ 1000 ´ 12 mS
Before Watchdog time-out occurs, the program must clear the 14-bit timer by writing 1 to WDTC.6 (CLRW). After 1 is written to this bit, the 14-bit timer, prescaler and this bit will be reset on the next instruction cycle. The Watchdog timer is cleared on reset.

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