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Appendix E: Watchdog Timer (WDT) Setting
WDT is widely applied to industry computers to monitor activities of CPU.
The programmed application triggers WDT with adequate timer setting
depending on its requirement. Before WDT counts down to zero, the func-
tional system will reset the counter. In case the WDT counter is not reset by
an abnormal system, it will counts down to zero and then reset the system
automatically.
This computer supports the watchdog timer up to 255 levels for users for
software programming. Below please take the source code written in C for a
WDT application example.
E.1 Source Code in C
/*-----
Include Header Area -----*/
#include "math.h"
#include "stdio.h"
#include "dos.h"
/**-------- index port 0x2e ---------*/
void main()
{
outportb(0x2e, 0x87);
/* initial IO port */
outportb(0x2e, 0x87);
/* twice, */
outportb(0x2e, 0x07);
/* point to logical device */
outportb(0x2e+1, 0x07);
/* select logical device 7 */
outportb(0x2e, 0xf5);
/* select offset f5h */
outportb(0x2e+1, 0x40);
/* set bit5 = 1 to clear bit5 */
outportb(0x2e, 0xf0);
/* select offset f0h */
outportb(0x2e+1, 0x81);
/* set bit7 =1 to enable WDTRST# */
outportb(0x2e, 0xf6);
/* select offset f6h */
outportb(0x2e+1, 0x05);
/* update offset f6h to 0ah :10sec */
outportb(0x2e, 0xF5);
/* select offset f5h */
outportb(0x2e+1, 0x20);
/* set bit5 = 1 enable watch dog time */
outportb(0x2e, 0xAA);
/* stop program F71869E, Exit */
}
Appendix
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Appendix
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