IEI Technology Enano-8523T, Руководство пользователя

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NOTE:
The following discussion applies to DOS environment. It is recommended
you contact IEI support or visit our website 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 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 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 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.
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