User's Guide
Revision. B3
April, 2001
Appendix
45
Watch Dog Timer Programming Procedure
•
Power on or reset the system
The initial value of WDT Control Register (D4~D0) is zero, when power is on or reset the system. The
following means the initial value of WDT ( 00000000b ) :
Bit Value
Mean
4 0 Select
Reset
3
0
Disable Watch Dog Timer
2, 1, 0 0 0 0
Select 64 second
•
Initialize the SQW of RTC (set SQW output period=0.5 second)
To initialize the SQW of RTC Component is to set the SQW signal which is output period=0.5 second.
It offers the basic frequency of the WDT counter.
The following is an example of
initializing the SQW signal program
in Intel 8086 assembly language.
; (Generate SQW = 0.5 Sec.)
Mov
dx, 70h
Mov
ax, 0Ah
Out
dx, al
; Out port 70h = 0Ah
Mov
dx, 71h
Mov
ax, 2Fh
Out
dx, al
; Out port 71h = 2Fh
; (enable the SQW output)
Mov
dx, 70h
Mov
ax, 0Bh
Out
dx, al
; Out port 70h = 0Bh
Mov
dx, 71h
Mov
ax, 0Ah
Out
dx, al
; Out port 71h = 0Ah
