PSB Speakers PSB-1688LF M1 user manual Watchdog Timer Configuration, Watchdog enable program

Chapter 3 Software Configuration

3-7. WATCHDOG TIMER CONFIGURATION

This board has watchdog timer function for monitoring whether 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 in “Reset/NMI/Clear Watchdog Selection” found in chapter 2. This is defined at I/O port 443H. When you want to enable the watchdog timer, please write I/O port 443H, and then the system will either reset itself or perform the NMI function. Likewise, when you want to disable the function, write I/O port 441H, the system will run the command to stop the Watchdog function.

In PSB-1688LF watchdog function, you must write your program so when it writes I/O port address 443 for enable watchdog and write I/O port address 441 for disable watchdog. The timer's intervals have a tolerance of 25% so you should program an instruction that will refresh the timer about every second.

The following program shows you how to program the watch timer in your program.

Watchdog enable program:

MOVAX, 000FH(choose the values you need; start from 0)

MOVDX, 443H

OUTDX, AX

Watchdog disable program:

MOVAX, 000FH(this value can be ignored)

MOVDX, 441H

OUTDX, AX

The Watchdog Timer control table is as follows:

	Level	Value	Time/sec	Level	Value	Time/sec
	1	F	0	9	7	64
	2	E	8	10	6	72
	3	D	16	11	5	80
	4	C	24	12	4	88
	5	B	32	13	3	96
	6	A	40	14	2	104
	7	9	48	15	1	112
	8	8	56	16	0	120
PSB-1688LF USER′S MANUAL							Page:3-9