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AR-B1520 User’s Guide

4. WATCHDOG TIMER

This section describes the use of Watchdog Timer. AR-B1520 is equipped with a programmable time-out period

watchdog timer that enable user to reset the system after a time out occur. Users can use simple program to enable

the watchdog timer, and program the timer in range of seconds or minutes, with maximum 255 seconds/minutes.

Once you enable the watchdog timer, the program will start the count down and when counting down to zero the

system will generate a reset signal to reset the system.

4.1 WATCHDOG TIMER SETTING

The watchdog timer is a circuit that maybe be used from your program software to detect crash or hang up.

The Watchdog timer is automatically disabled after reset. Once you enabled the watchdog timer, your program

should trigger the watchdog timer every time before it times out. After you trigger the watchdog timer, the timer will

be set to zero and start to count again. If your program fails to trigger the watchdog timer before times out, it will

generate a reset pulse to reset the system .

Please refer to the following table in order to properly program Watchdog function.

Users could test watchdog function under ‘Debug’ program as follows:

C:>debug

o 2e 87

;Extended Functions Enable Register

o 2e 87 ;Extended Functions Enable Register

o 2e 07 ;EFIR=EFER (Extended Functions Index Register)

point to Logical Device Number Reg.

o 2f 08

;EFDR=EFIR+1 (select logical device 8, Watchdog )

o 2e f4 ;select CRF4 (to set Watchdog Timer Value)

o 2f 02 ;set the Watchdog timer to 2 seconds. (00 to disable, max FF)

o 2e 30 ;select device 30

o 2f 01 ;enable

q ;Quit debug

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Acrosser AR-B1520 Manuel d'utilisateur Page 15