ADS Technologies AR-B1851 manual Appendix A. Watchdog Timer

AR-B1851 User’s Guide

Appendix A. Watchdog Timer

The WDT(Watch Dog Timer)is used to generate a variety of output signals after a user programmable cont. The WDT is suitable for use in the prevention of system lock-up, such as when software becomes trapped in a deadlock. Under these sort of circumstances, the timer will count to zero and the selected outputs will be driven. Under normal circumstance, the user will restart the WDT at regular intervals before the timer counts to zero.

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 watchdogtimer, 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 or trigger the IRQ9 signal in order to tell your system that the watchdog time is out.

User could test watch dog function under ’Debug.exe’ program as follows:

WDT Example	Description
o 2e 87	;Extended Functions Enable Register
o 2e 87	;Extended Functions Enable Register
o 2e 07	;EFIR=EFER(Extended Function Index
	Register)point to Logical Device Number Reg.
o 2f 08	;EFDR=EFIR+1, select logical device 8
o 2e 30	;select CR30
o 2f 01	;update CR30 with value 01H
o 2e f6	;select CRF6
o 2f 08	;update CRF6 with value 08H,(8sec reset)
g	;go
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