Acnodes PC 6415 - Manual (Page 100)

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All rights reserved. Product description and product specifications
are subject to change without notice. For latest product information,
please visit Acnodes’ web site at www.acnodes.com.
PC 6415
15” Fanless Panel PC
A. WATCHDOG TIMER
NOTE:
The following discussion applies to DOS environment. IEI support is contacted or the IEI
website visited for specific drivers for more sophisticated operating systems, e.g., Windows and
Linux.
The Watchdog Timer is provided to ensure that standalone systems can always recover from cata-
strophic conditions that cause the CPU to crash. This condition may have occurred by external EMIs or
a software bug. When the CPU stops working correctly, Watchdog Timer either performs a hardware
reset (cold boot) or a Non-Maskable Interrupt (NMI) to bring the system back to a known state.
A BIOS function call (INT 15H) is used to control the Watchdog Timer.
INT 15H:
Call sub-function 2 to set the time-out period of Watchdog Timer first. If the time-out value is not zero,
the Watchdog Timer starts counting down. When the timer value reaches zero, the system resets. To
ensure that this reset condition does not occur; calling sub-function
2 must periodically refresh the Watchdog Timer. However, the watchdog timer is disabled if the time-
out value is set to zero.
A tolerance of at least 10% must be maintained to avoid unknown routines within the operating system
(DOS), such as disk I/O that can be very time-consuming.
NOTE:
When exiting a program it is necessary to disable the Watchdog Timer, otherwise the system resets.