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Appendix 1 - Watch Dog Timer
Stingray II+ User's Guide
A1-4
S
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Clear the WDT
Repeatedly read WDT Configuration Port and the interval cannot be lonĆ
ger than the preset time, otherwise, the WDT will generate NMI or Reset
signal for the system.
The following is an example of
clear the WDT program in Intel 8086
assembly language.
; ( Clear the WDT)
Mov dx, F2h ;Setting the WDT configuration port
In al, dx
Note: Before running WDT, you must clear the WDT, making sure the
initial value is zero before enabling the WDT.
S WDT Control Register (Write to WDT configuration port)
You can set the WDT Control Register to control the WDT working mode.
The initial value of the WDT Control Register is as the following.
; (Setting the WDT Control Register as AL)
Mov
al, 0h ; Setting initial value = 0 for the WDT Control
Register
You can select the tollowing options:
1. Select NMI or Reset: decide D4 value in F2.
For Reset Mode, set D4 = 0
Mov al, 11101111b ; Select Reset
For NMI Mode, set D4 = 1
Mov al, 00010000b ; Select NMI
2. Select the time-out intervals of WDT (decide the values of D2, D1, D0
in F2 )
Example: D2~D0 = 0, the time-out interval will be 64 sec.
Mov al, 11111000b ; Setting the time-out interval as 64 sec.