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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
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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.
E
2
KEY™ FUNCTION
The SBC-370 provides an E
2
KEY™ function for system integrators. Based on the E
2
KEY
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 E
2
KEY 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 E
2
KEY 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