protech ProX-1550, Руководство пользователя

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Chapter 3 Software Configuration
Page:3-10
Prox-1550 USER
′
S MANUAL
3-6. 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 JP6 as described 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 , 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.
The Prox-1550 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, 0443H
OUTDX, AX
Watchdog disable program:
MOVAX, 000FH (this value can be ignored)
MOVDX, 0441H
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