Intel SBC-370 manual Operating Humidity, Watchdog Timer, E2KEY Function

Operating Humidity

•5 - 95%, non-condensing

WATCHDOG TIMER

The Watchdog Timer is provided to ensure that standalone systems can recover from catastrophic conditions that cause the CPU to crash. This condition can occur from ex- ternal EMI or a software bug. When the CPU stops working correctly, hardware on the board will either perform a hardware reset (cold boot) or a Non-Maskable Interrupt (NMI) to bring the system back to a known state.

Two I/O ports control the Watchdog Timer:

443 (hex)	Read	Enable to refresh the Watchdog Timer
043 (hex)	Read	Disable the Watchdog Timer

To enable the Watchdog Timer, a read from I/O port 443H must be performed. This will enable and activate the countdown timer which will eventually timeout and either reset the CPU or cause a NMI, depending on the setting of JP5. To ensure that this reset condition does not occur, the Watchdog Timer must periodically be refreshed by reading the same I/O port 433H. This must be done within the time- out period that is selected by JP12.

A tolerance of at least 20% must be maintained to avoid unknown routines within the operating system (DOS), such as disk I/O that can be very time consum- ing. Therefore, if the timeout period has been set to 10 seconds, the I/O port 443H must be read within 7 seconds.

Note: When exiting a program, it is necessary to disable the Watchdog Timer, otherwise the system will reset.

E2KEY™ FUNCTION

The SBC-370 provides an E2KEY™ function for system integrators. Based on the E2KEY utility, you can freely store the ID Code, Password, or Critical Data in the 1Kbit EEPROM. Because the EEPROM is nonvolatile memory, you don't have to worry about losing important data.

The E2KEY utility is based on a 1Kbit EEPROM which is configured to 64 words (from 0 to 63). You can access (read or write) each word at any time.

The E2KEY utility is provided on a CD-ROM with your system. The software utility will include four files as files:

•README.DOC

•E2KEY.OBJ

•EKEYDEMO.C

•EKEYDEMO.EXE

9 Features