Advantech ARK-5420 Series User Manual

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Advantech ARK-5420 Series User Manual Manual pdf 76 page image

ARK-5420 User Manual 64A.1 Programming the Watchdog TimerThe ARK-5420's watchdog timer can be used to monitor system software operationand take corrective action if the software fails to function within the programmedperiod. This section describes the operation of the watchdog timer and how to pro-gram it.A.1.1 Watchdog Timer OverviewThe watchdog timer is built into the super I/O controller SMSC SCH3114. It providesthe following user-programmable functions: Can be enabled or disabled via user program Timer can be set from 1 to 255 seconds or 1 to 255 minutes Generates an interrupt or resets signal if the software fails to reset the timer before time-outA.1.2 Programming the Watchdog TimerThe I/O port address of the watchdog timer is 680h (hex).Table A.1: Watchdog Timer RegistersAddress: 680h(hex) RegisterRead/WriteDescription65 (hex) writeSet seconds or minutes as units for the timer.Write 0 to bit 7: set second as counting unit. [default]Write 1 to bit 7: set minutes as counting unit.66 (hex) write0: Stop timer [default]01~FF (hex): The amount of the count, in seconds or min- utes,depends on the value set in register 65 (hex). This number decideshow long the watchdog timer waits for strobe before generating aninterrupt or reset signal. Writing a new value to this register canreset the timer to count withthe new value.67 (hex) read/writeConfigure watchdog timerBit 1:Write 1 to enable keyboard to reset the timer, 0 to dis- able.[default]Bit 2: Write 1 to enable mouse to reset the timer, 0 to dis-able.[default]Bit 7~4: Set the interrupt mapping of watchdog timer:1111=IRQ15……0011=IRQ30010=IRQ20001=IRQ10000=Disable [default]68 (hex) read/writeControl watchdog timerBit0: Read watchdog state; 1=Timer timeoutBit2: Write 1 to immediately generate timeout signal, and automat-ically return to 0 (Write only).Bit3: Writer 1 to allow triggering of timer timeout when P20 is effec-tive, 0 to disable. [default]