110502
PRODUCT MANUAL EPX-C380
17
Watchdog Timer
The EPX-C380 features an advanced watchdog timer which can be used to guard against software lockups. Three
interfaces are provided to the watchdog timer. The Advanced interface is the most flexible and recommended for new
designs. The other two interface options are provided for software compatibility with older WinSystems single board
computers.
Advanced
The watchdog timer can be enabled in the BIOS Settings by entering a value for Watchdog Timeout on the Intel → Super
I/O Control screen. Any non-zero value represents the number of minutes prior to reset during system boot. Once the
operating system is loaded, the watchdog can be disabled or reconfigured in the application software.
NOTE:
It is recommended that a long timeout be used 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 timeout value other than zero to the I/O address
566h and disabled by writing
00h
to this I/O 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 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. The timeout value written to address 566h is in seconds if port 565 bit 7 equals
1
.
Port Address
Value
Reset Interval
1EEH
00h
DISABLED
01h
3 SECONDS
03h
30 SECONDS
05h
300 SECONDS
1EFH
ANY
RESET TIMER
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.
Watchdog Timer Examples
Standard (requires changing the default I/O ranges within in the BIOS)
The watchdog can be enabled or disabled via software by writing an appropriate timeout value to I/O port 1EEH. See the
chart provided below.
Preliminary
