Arbor Technology EmETXe-a10M0, User Manual

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Appendix
Appendix D: Watchdog Timer (WDT) Setting
WDT is widely used for industry application to monitor the activity of CPU. Ap-
plication software depends on its requirement to trigger WDT with adequate
timer setting. Before WDT time out, the functional normal system will reload
the WDT. The WDT never time out for a normal system. The WDT will not be
reloaded by an abnormal system, then WDT will time out and reset the system
automatically to avoid abnormal operation.
This board supports 255 levels watchdog timer by software programming I/O
ports. Below are the source codes written in C, please take them as WDT ap-
plication example.
/*---------------------------------------------------------------------------*/
#include <math.h>
#include <stdio.h>
#include <dos.h>
int iWDTCount;
int sioIndex = 0x2E; // or 0x4E
int sioData = 0x2F; // or 0x4F
int main(void)
{
unsigned char iCount;
printf(“WDT Times ( 1 ~ 255 ) : “);
scanf(“%d”,&iCount);
printf(“\n”);
WDT_Start(iCount);
return 0;
}
void WDT_Start(int iCount)
{
int iData;
outportb(sioIndex, 0x87); /* Enable Super I/O */
outportb(sioIndex, 0x87);
outportb(sioIndex, 0x07); /* Select logic device – WDT */
outportb(sioData, 0x07);
outportb(sioIndex, 0x29); /* Enable WDTRST# Pin */
iData = inportb(sioData);
iData = iData & 0xEF;
outportb(sioData, iData); /* The pin function is WDTRST# */
outportb(sioIndex, 0x30); /* Enable WDT */
outportb(sioData, 0x01);