SBC81870 SERIES USER'S MANUAL VERSION A1 SEPTEMBER ...

SBC81870 Intel ® Pentium ® M w/ DDR/VGA/Dual LAN3.8 Watchdog Timer ConfigurationThis board has watchdog timer function for monitoringwhether the system is still work or not after a period of time.The user can select watchdog timer to system reset or NMI(Non Maskable interrupt) depending on the jumper set inchapter 2. This is defined at I/O port 443H. When you wantto enable the watchdog timer, please write I/O port 443H,and then the system will either reset itself or perform the NMIfunction. Likewise, when you want to disable the function,write I/O port 441H, the system will run the command to stopthe Watchdog function.In SBC81870 watchdog function, you must write yourprogram so when it writes I/O port address 443 for enablewatchdog and write I/O port address 441 for disablewatchdog. The timer's intervals have a tolerance of 25%(but for level 1 and 2, the tolerance is 4%), so you shouldprogram an instruction that will refresh the timer about everysecond.The following program shows you how to program the watchtimer in your program.Watchdog enable program:MOVAX, 000FH(choose the values you need; start from 0)MOVDX, 443HOUTDX, AXWatchdog disable program:MOVAX, 000FH(this value can be ignored)MOVDX, 441HOUTDX, AXSoftware Utilities 49