Specifications

Chapter 3 Hardware
CoreModule 420 Reference Manual 43
Watchdog Timer
The watchdog timer (WDT) restarts the system if an error or mishap occurs, allowing the system to
recover from the mishap, even though the error condition may still exist. Possible problems include
failure to boot properly, loss of control by the application software, failure of an interface device,
unexpected conditions on the bus, or other hardware or software malfunctions.
The WDT (watchdog timer) can be used both during the boot process and during normal system
operation.
• During the Boot process – If the OS fails to boot in the time interval set in the BIOS, the system
will reset.
Enable the Watchdog Timer (sec) field in the BIOS and Hardware Settings screen of BIOS Setup.
Set the WDT for a time-out interval in seconds, between 1 and 255, in one second increments.
Ensure you allow enough time for the operating system (OS) to boot. The OS or application
must tickle (reset) the WDT before the timer expires. This can be done by accessing the
hardware directly or through a BIOS call.
• During System Operation – An application can set up the WDT hardware through a BIOS call, or
by accessing the hardware directly. Some Ampro Board Support Packages provide an API to the
WDT. The application must tickle (reset) the WDT before the timer expires or the system will be
reset. The BIOS implements interrupt 15 function 0x0C3h to manipulate the WDT.
• Watchdog Code examples – Ampro has provided source code examples on the CoreModule 420
Doc & SW CD-ROM illustrating how to control the WDT. The code examples can be easily
copied to your development environment to compile and test the examples, or make any desired
changes before compiling. Refer to the WDT Readme file in the Miscellaneous Source Code
Examples subdirectory, under the Support Software menu on the CoreModule 420 Doc & SW
CD-ROM.