EPX-C414/Configuration
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Two interfaces are provided to the watchdog timer. The Advanced interface is the most
flexible and recommended for new designs. The other interface option is provided for
software compatibility with older WinSystems single-board computers.
7.8.1 Advanced
Enable the watchdog timer in the BIOS settings by entering any non-zero value for
Watchdog Timeout on the Intel Super I/O Control screen. A non-zero value represents
the number of minutes prior to reset during system boot. When the operating system is
loaded, the watchdog can be disabled or reconfigured in the application software.
NOTE
WinSystems recommends using a long timeout if the watchdog is enabled when trying
to boot any operating system.
The watchdog can be enabled, disabled, or reset by writing the appropriate values to the
configuration registers located at I/O addresses 565h and 566h. The watchdog is
enabled by writing a non-zero timeout value to the I/O address 566h, and is disabled by
writing 00h to the same address. The watchdog timer is serviced by writing the desired
timeout value to I/O port 566h. If the watchdog has not been serviced within the allotted
time, the circuit resets the CPU.
The timeout value can be set to anywhere from 1 second to 255 minutes. If port 565h
bit 7 equals 0, the timeout value written into I/O address 566h is in minutes. If port 565
bit 7 equals 1, the timeout value written to address 566h is in seconds.
Table 19:
Watchdog Timer Examples
Port Address
Port Bit 7
Value
Port Address
Value
Reset Interval
565h
x
566h
00h
DISABLED
565h
1
566h
03h
3 seconds
565h
1
566h
1Eh
30 seconds
565h
0
566h
04h
4 Minutes
565h
0
566h
05h
5 Minutes
Software watchdog timer PET = PORT 566h, write the timeout value.
