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AR-B1851 User’s Guide
AR-B1851
35
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