Contec SPI-6941-LV - Watch-Dog-Timer (WDT) Setting

CHAPTER 5 – S o f twa r e U tilitie s
46 SPI-6941-LV
5 . 2 W a t c h - D og - Ti m e r ( W D T ) S e tt ing
WDT is widely used for industry application to monitoring the activity of CPU.
Application 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 reload by an abnormal system, then WDT
will time out and reset the system automatically to avoid abnormal operation.
SPI-6941-LV supports 16 levels watchdog timer by software programming I/O
ports. Write any value to I/O address 0441H will disable Watch-Dog-Timer. Write setting code
(please reference to WDT Setting Table) to I/O 0443h will re-load WDT.
Below is an assembly program example for disable and load of WDT.
MOV DX,0441H ; REM Write any value to 0441H, disable WDT
OUT DX,AX;
MOV AX,0001H ;
WDT timer = 28 Sec
MOV DX,0443H
OUT DX,AX ;
REM trigger WDT with timer setting
Timer Value Table
V a lue Ti m er V a lue Ti m er V a lue Ti m er V a lue Ti m er
0 30 sec 4 22 sec 8 14 sec C 6 sec
1 28 sec 5 20 sec 9 12 sec D 4 sec
2 26 sec 6 18 sec A 10 sec E 2 sec
3 24 sec 7 16 sec B 8 sec F
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