Moxa UC-7110-LX [37/46] Wdt watch dog timer

UC-7101/7110/7112 Software User’s Manual UC-7101/7110/7112 Device API

5-3

WDT (Watch Dog Timer)

1. Introduction

The WDT works like a watch dog function. You can enable it or disable it. When the user enables

WDT but the application does not acknowledge it, the system will reboot. You can set the ack time

from a minimum of 50 msec to a maximum of 60 seconds.

2. How the WDT works

The sWatchDog is disabled when the system boots up. The user application can also enable ack.

When the user does not ack, it will let the system reboot.

Kernel boot

…..

….

User application running and enable user ack

….

3. The user API

The user application must include <moxadevic.h>, and link moxalib.a. A makefile example is

shown below:

all:

arm-elf-gcc –Wl, -elf2flt –o xxxx xxxx.c -lmoxalib

int swtd_open (void)

Description

Open the file handle to control the sWatchDog. If you want to do something you must first do this

and keep the file handle for other uses.

Input

None

Output

The return value is the file handle. If there is an error, it will return a negative value.

Use errno() to retrieve errors.

int swtd_enable (int fd, unsigned long time)

Description

Enable application sWatchDog. You must do an ack after this process.

Input

int fd—the file handle, from the swtd_open() return value.

unsigned long time—The time you wish to ack sWatchDog periodically. You must ack the

sWatchDog before timeout. If you do not ack, the system will be reboot

automatically. The minimum time is 50 msec, the maximum time is 60

seconds. The time unit is msec.