ADLINK Technology LittleBoard 735, Reference Manual

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Chapter 3 Hardware
38 Reference Manual LittleBoard 735
Hot (Serial) Cable
To convert a standard serial cable to a Hot Cable, specific pins must be shorted together at the Serial port
connector or at the DB9 cable connector. For example, short the RTS (7) and RI (9) at the rear of the
respective DB9 cable connector as shown in
Figure 3-3 .
Figure 3-3. Hot Cable Jumper
Watchdog Timer
The watchdog timer (WDT) restarts the system if a mishap occurs, ensuring proper start-up after the
interruption. Possible problems include failure to boot properly, the application software’s loss of control,
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.
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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 Boot Settings Configuration of BIOS Setup. Set the WDT for a time-out interval in
seconds, between 1 and 255, in one-second increments in the Boot Setting Configuration screen. Ensure
you allow enough time for the boot process to complete and for the OS to boot. The OS or application
must tickle the WDT as soon as it comes up. This can be done by accessing the hardware directly or
through a BIOS call.
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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 the WDT in the time set when the WDT is initialized or the
system will be reset. You can use a BIOS call to tickle the WDT or access the hardware directly.
The BIOS implements interrupt 15 function 0C3h to manipulate the WDT.
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Watchdog Code examples – ADLINK has provided source code examples on the LittleBoard 735
Support Software CD-ROM illustrating how to control the WDT. The code examples can be easily
copied to your development environment to compile and test the examples, or make any desired
changes before compiling. Refer to the WDT Readme file on the LittleBoard 735 Support Software
QuickDrive.
Optional CPU Fan
Table 3-22 lists the pin signals of the optional CPU Fan, which uses 3 pins, single row, with 0.100"
(2.54mm) pitch.
Note: The shaded areas denote power or ground.
Table 3-22. Optional CPU Fan (J34)
Pin # Signal Description
1 Fan_Tach Fan Tachometer – This signal indicates Fan speed
2 VCC +5.0 volts DC +/- 5%
3 GND Ground and Modulation
Standard DB9 Cable
Connector (Female)
Rear View
5 4 3 2 1
9 8 7 6
LB735Hotcable