System Installation
ROBO-8112VG2AR User’s Manual
3-8
3.5
WDT Function
The working algorithm of the WDT function can be simply described as a counting
process. The Time-Out Interval can be set through software programming. The
availability of the time-out interval settings by software or hardware varies from
boards to boards.
ROBO-8112VG2AR allows users control WDT through dynamic software
programming. The WDT starts counting when it is activated. It sends out a signal to
system reset or to non-maskable interrupt (NMI), when time-out interval ends. To
prevent the time-out interval from running out, a re-trigger signal will need to be
sent before the counting reaches its end. This action will restart the counting process.
A well-written WDT program should keep the counting process running under
normal condition. WDT should never generate a system reset or NMI signal unless the
system runs into troubles.
The related Control Registers of WDT are all included in the following sample
program that is written in C language. User can fill a non-zero value into the Time-out
Value Register to enable/refresh WDT. System will be reset after the Time-out
Value to be counted down to zero. Or user can directly fill a zero value into Time-out
Value Register to disable WDT immediately. To ensure a successful accessing to the
content of desired Control Register, the sequence of following program codes
should be step-by-step run again when each register is accessed. Additionally, there
are maximum 2 seconds of counting tolerance that should be considered into user’
application program. For more information about WDT, please refer to IT8728F/CXS
data sheet.
There are two PNP I/O port addresses that can be used to configure WDT,
1) 0x2E:EFIR (Extended Function Index Register, for identifying CR index number)
2) 0x2F:EFDR (Extended Function Data Register, for accessing desired CR)
Below are some example codes, which demonstrate the use of WDT.
#include <stdio.h>
#include <conio.h>
#include <dos.h>
#define SIO_Port 0x2E
#define SIO_Port2
0x4E
#define GPIO_LDN
0x07
void Enter_IT872x_SIO() {
outportb(SIO_Port,
0x87);
outportb(SIO_Port,
0x01);
outportb(SIO_Port,
0x55);
outportb(SIO_Port,
0x55);
}
