Operating Humidity
•5 - 95%,
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
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
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
•README.DOC
•E2KEY.OBJ
•EKEYDEMO.C
•EKEYDEMO.EXE
9 | Features |