ADLINK ETX-PVR - Manual (Page 49)

Chapter 3 Hardware
ETX-PVR Reference Manual 43
Watchdog Timer (WDT)
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 operating system fails to boot in the time interval set in the BIOS, the
system will reset.
The Watchdog Timer (WDT) is enabled and configured in the Boot settings screen of the BIOS Setup
Utility. 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 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 ADLINK Board Support Packages provide an API interface 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 0C3h to manipulate the WDT.
• Watchdog Code examples – ADLINK will provide code examples on the ETX-PVR Support Software
QuickDrive illustrating how to control the WDT. The code examples can be easily copied to your
development environment to compile and test or to make any desired changes before compiling. Refer
to the WDT README file on the ETX-PVR Support Software QuickDrive.
Power Interface
The ETX-PVR draws its input voltage (+5V) through the four connectors (X1, X2, X3, X4) on the custom
baseboard, which requires an external power supply, typically an ATX power supply or other power source
as the application requires. The ETX-PVR generates its own internal voltages onboard, including the CPU
core voltages and requires the externally supplied +5 volts DC +/- 5%.
The –5V, –12V, and +12V voltages used for the PCI and ISA buses and the LVDS video header are supplied
to the baseboard and ETX-PVR module from the externally connected power supply, typically an ATX
power supply.
Power and Sleep States
The following information only applies if an ATX power supply is connected to the ETX baseboard on
which the ETX-PVR is installed. If a non-ATX power supply is used, then the ETX-PVR is only controlled
by the Power-On/Off switch on the power supply and the various sleep states are not available. The ACPI
sleep states are OS dependent and not available if your OS does not support power management based on the
ACPI standard. The signals used for control of the ATX power supply and sleep states in general is
described in more detail under Power Control Signals and Power Management Signals earlier in this
chapter.
Power-On Switch
The Power-On switch, on or connected to the ETX Baseboard, turns the ETX-PVR and its attached power
supply to a fully powered-on condition, if you are using an ATX power supply and an OS that supports sleep
states. If the operating system (OS) supports sleep states, the OS will turn off the ETX-PVR and its power
supply during the OS shut down process. Typically, the Power-On switch will also transition the ETX-PVR,
the ETX baseboard, and its power supply between a fully powered-on state and the various sleep states,
including a fully powered-off state. If the OS does not support sleep states, then the Power-On switch only
turns power On or Off to the ETX-PVR and its baseboard.
Typically, an OS that supports ACPI, also allows the Power-On switch to be configured through a user
interface. The Power-On switch for the ETX-PVR must be provided on, or connected to the baseboard.