ADLINK Technology cPCI-3920 Series, User Manual

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62 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.
6.2 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();