User`s manual

CyberResearch
®
CPU Cards CZGG LU-10-X Series
CyberResearch, Inc. 147
25 Business Park Drive P: [phone]; F: [phone]
Branford, CT USA www.cyberresearch.com
NOTE:
The following discussion applies to the DOS environment. It is
recommended you contact CyberResearch support or visit our website for
specific drivers for other operating systems.
The Watchdog Timer is provided to ensure that standalone systems can always recover
from catastrophic conditions that cause the CPU to crash. This condition may have
occurred by external EMI 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:
AH – 6FH Sub-function:
AL – 2: Sets the Watchdog Timer’s period.
BL: Time-out value (Its unit-second is dependent on the item “Watchdog
Timer unit select” in CMOS setup).
Table B-1: AH-6FH Sub-function
You have to 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. While the timer
value reaches zero, the system will reset. To ensure that this reset condition does not
occur, calling sub-function 2 must periodically refresh the Watchdog Timer. However, the
Watchdog timer will be disabled if you set the time-out value to be 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.