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Changing the I/O Port Address
The setup program, WDTSETUP.EXE, changes the I/O port
address that the software uses to communicate with watchdog timer.
This address must match the setting of the jumper switches on the
watchdog timer. The program updates keys in the registry for the
device driver. In order to update these keys under Windows NT
Server, the user must be logged in as the administrator or have
administrator rights. Windows NT Workstation and Windows 95
allow all users to modify these keys. Under Windows NT, both
server and workstation, the changes made by the setup program
take effect the next timer the computer is restarted. Under Windows
95, the changes are effective immediately, but any program that is
using the watchdog timer when the change is made must be
restarted for the changes to take effect.
Disk Caching
Both Windows NT and Windows 95 use disk caching to speed
up access of the hard drive. This means that the operating system
decides when to write data to the disk instead of it being done when
your application writes it. Rebooting the computer with the watchdog
timer with write-behind caching enabled may cause the loss of all
data in the write-behind cache.
Existing DOS Programs
The NT device driver does not allow existing DOS programs to
communicate with the watchdog timer. DOS programs will work
under Windows 95, because Windows 95 allows direct access to the
I/O ports of the computer.
Windows 3.11
Windows 3.11, just like DOS, allows full access to the I/O ports
of the computer, so a simple OUT command can be used to
communicate with the watchdog timer. A 16-bit dynamic-link library
(DLL) is supplied to provide a common interface to the watchdog
timer as in Windows 95 and Windows NT. The commands are
explained in the command reference section of this chapter.
14
Documentation Number ATxWDT-1303
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