Watchdog Timer, Serial Console Setup

Chapter 3

Hardware

Serial Console Setup

The serial console feature is implemented by connecting a standard null modem cable or a modified serial cable (or “Hot Cable”) between one of the serial ports, such as Serial 1 (J5A), and the serial terminal or a PC with communications software. The BIOS Setup Utility controls the serial console settings on the ReadyBoard 700. Refer to Chapter 4, BIOS Setup for the settings of the serial console option, the serial terminal, or PC with communications software and the connection procedure.

Hot (Serial) Cable

To convert a standard serial cable to a Hot Cable, certain pins must be shorted together at the Serial port connector or at the DB9 connector. For example, short the RTS (7) and RI (9) on the respective DB9 port connector as shown in Figure 3-3.

1 2 3 4 5

Standard DB9 Serial Port Connector (Female)

Rear View 6 7 8 9

Figure 3-3. Hot Cable Jumper

RB700_hotcable

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.

•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 in the Advanced BIOS Features screen. Ensure you allow enough time for the boot process to complete and for the OS to boot. The OS or application must tickle (turnoff) the WDT as soon as it comes up. 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 Ampro Board Support Packages provide an API interface to the WDT. The application must tickle (turnoff) 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.

•Watchdog Code examples – Ampro has provided source code examples on the ReadyBoard 700 Doc & SW 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 in the Miscellaneous Source Code Examples subdirectory, under the ReadyBoard 700 Software menu on the ReadyBoard 700 Doc & SW CD-ROM.

Reference Manual

ReadyBoard 700