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B. appendix b: watchdog timer, B.1 most introduction, B.2 detail register descriptions – Lanner LEC-2050 User Manual

Page 32: B.2.1 to used the watch-dog timer

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LEC-2050 Fanless Embedded System User’s Manual

32

B. Appendix B: Watchdog Timer

B.1 Most Introduction

systems need to be self-reliant. If an error should occur it is typically not possible to wait for

the system to be rebooted manually. In some cases, such as space probes, the system is

simply not accessible to human operators. If such systems should ever hang, they would be

permanently disabled. In other cases, the speed at which a human operator would reset the
system would be too slow to meet the uptime requirements of the product.

A watchdog timer is a piece of hardware that can be used to automatically detect system

anomalies and reset the processor in the case any problems are found. Generally speaking,
a watchdog timer is based on a counter that counts down from an initial value to zero. The

software selects the counter's initial value and periodically restarts it. Should the counter

reach zero before the software restarts it, the software is presumed to be malfunctioning,

and the processor's reset signal is asserted. Thus, the processor will be restarted as if a
human operator had cycled the power.

B.2 Detail Register Descriptions

A watchdog action consists of a series of watchdog instructions. A watchdog instruction is

the operation on a register region. This section describes the detail register in LPD I/O

(W83697HG)

B.2.1 To used the watch-dog timer

For DOS system:

Execute the EM9765WD1.EXE file under DOS, then key-in 0~255. The system will reboot
automatically according to the time-out you set.