ADLINK Technology cPCI-3920 Series Uživatelský manuál stáhnout pdf (Strana 54)

40 Watchdog Timer

the internal IO to control the WDT and retrieve its status. The basic

functions of the WDT include:

X Setting the watchdog timeout interval

X Starting the timer countdown

X Selecting 1 step or 2 step WDT

X Enabling or disabling WDT

X Reloading the timeout value to keep the watchdog from tim-

ing out

X Setting the range of the timeout period from 1 µs to 1 sec-

ond, or from 1 ms to 1050 seconds

When the watchdog times out, it will send a RESET signal to the

system.

7.2 Using the Watchdog Timer in an Application

The following section describes the WDT functions in an applica-

tion. The WDT reset function is explained in the previous section.

This can be controlled through the registers in the WDT unit of the

Intel 3100 chipset .

An application using the reset feature enables the watchdog func-

tion, sets the count-down period, and reloads the timeout value

periodically to keep it from resetting the system. If the timer count-

down value is not reloaded, the watchdog resets the system hard-

ware after its counter registers zero.

A detailed programming sample is provided below:

#include<dos.h>

#include<conio.h>

#include<stdio.h>

#include<stdlib.h>

#defineconfig_port_index0x4E

#defineconfig_port_data0x4F

/* Pre-declaration */

/* access configuration registers routines */

void enter_config_mode();

void exit_config_mode();

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ADLINK Technology cPCI-3920 Series Uživatelský manuál Strana 54