Casio HS-3000/4M JP9: Watchdog Timer Active Type Select, JP14: Watchdog Timer Out Period Select, JP9, PINS, PINS, PINS, PINS, Period, Description

JP9: Watchdog Timer Active Type Select

JP9	Description	1
Short 1-2 (default)	System Reset
Short 2-3	Active NMI
Open	Disabled
		3

JP14: Watchdog Timer Out Period Select
Period	PINS 1-2	PINS 3-4	PINS 5-6	PINS 7-8
1 sec	Open	Open	Short	Open
(default)
					2
2 sec	Open	Open	Short	Short
10 sec	Open	Short	Open	Open	1
20 sec	Open	Short	Open	Short
110 sec	Short	Open	Open	Open
220 sec	Short	Open	Open	Short

The watchdog timer is disabled after the system power-on. The watchdog timer can be enabled by a Enable cycle with reading the control port (443H), a Refresh cycle with reading the control port (443H) and a Disable cycle by reading the watchdog timer disable control port (043H). After a Enable cycle of WDT, user must constantly proceed a Refresh cycle to WDT before its period setting comes ending of every 1, 2, 10, 20, 110 or 220 seconds (Please reference to the selection table of JP14 for WDT Time Out period setting). If the Refresh cycle does not active before WDT period cycle, the onboard WDT architecture will issue a Reset or NMI cycle to the system. The watchdog timer controlled by two I/O ports.

443H	I/O Read	Enable/Refresh cycle
043H	I/O Read	Disable cycle

The following sample program shows how to Enable, Disable and Refresh the watchdog timer：

WDT_EN_RF	EQU	0433H
WDT_DIS	EQU	0043H
WT_Enable	PUSH	AX	; keep AX DX
PUSH	DX
MOV	DX,WDT_EN_RF		; enable the WDT
IN	AL,DX
POP	DX		; get back AX, DX
POP	AX
RET

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