Ampro Corporation MightyBoard 821 Power Interfaces, Watchdog Timer, ATX Power Supply Interface

Models: MightyBoard 821

1 38
Download 38 pages 37.82 Kb
Page 31
Image 31
Watchdog Timer

Chapter 3


Table 3-11. Infrared (IrDA) Interface Pin/Signal Descriptions (J7) (Continued)




IR Receive Data Ground

Note: The shaded area denotes power or ground.

Watchdog Timer

The watchdog timer (WDT) restarts the system if a mishap occurs. Possible problems include failure to boot properly, the application software’s loss of control, 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.

Enable the WDT in the Advanced BIOS Features of BIOS Setup. Set the WDT for a time-out interval in seconds, between 2 and 255, in one second increments. Ensure you allow enough time for the operating system (OS) to boot. The OS or application must tickle the WDT before the timer expires.

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 interface to the WDT. The application must tickle 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 – Ampro has provided source code examples on the MightyBoard 821 Support Software DVD illustrating how to control the WDT. (Refer to the WDT Readme file in the Miscellaneous Source Code Examples subdirectory, under the MightyBoard 821 Software menu on the MightyBoard 821 Support Software DVD.)

Power Interfaces

ATX Power Supply Interface

The power supply interface, J2, uses a 20-pin interface that connects directly to a standard ATX power supply. The MightyBoard 821 requires +12 volts for operation and all the onboard voltages, including the CPU core voltages, are derived from the externally supplied +12 volts DC +/- 5%. The ATX power supply interface provides -5V, -12V, +5V, +3.3V and +12V to the MightyBoard 821, but not all interface pins are connected at the MightyBoard 821. Refer to the Table 3-12for more information.

Table 3-12shows the pin signals for power interface (J2), which has 20-pins, two rows, consecutive (1, 11) with 0.165" (4.2mm) pin spacing.

Table 3-12. ATX Power Supply Interface Pin/Signal Descriptions (J2)

Pin #



1, 2, 11


+3.3 volts – This voltage used for PCI bus.

3, 5, 7



4, 6,


+5 volts +/- 5% – This is the main input voltage to the MightyBoard and it

19, 20


generates the other voltages used on the MightyBoard 821.



Not connected (Power Ok or Good)






+5V, 100mA Standby voltage – Input to MightyBoard from ATX type power



supply to power specific components on the board during standby.



+12 volts +/- 5% – This provides voltage to the CPU Fan, LCD backlite supply



and PCI bus.



-12 volts – This voltage goes to PCI bus only




MightyBoard 821

Reference Manual


Page 31
Image 31
Ampro Corporation MightyBoard 821 Power Interfaces, Watchdog Timer, ATX Power Supply Interface, Pin #, Signal, Description