ADLINK PCI-7260 - Manual (Page 41)

Operation Theorem 31
4.3 Watchdog Timer
In safety-critical applications, users can enable the watchdog timer
function on PCI 7260 to automatically set the relay pattern to pre-
set state, in case the operating system or PCI 7260 crashes. To
access this function, users must first configure the watchdog timer
overflow counter by windows API. Generally the trigger source
would come from the onboard 30-bit watchdog timer.
The watchdog timer overflow interval can be programmed through
Windows API. After enabling the watchdog timer, users must peri-
odically reset the timer by software command. If the timer is not
being reset within the specified interval, the WDT module will gen-
erate an overflow signal and set the relay pattern to the one speci-
fied by users. This function is disabled by default. For more
information, please refer to the software programming users’
guide.
The Watch Dog Timer function operation flow is as follows:
1. Load the WDTimer counter value through the function
_7260_WDTimerSReload_Config(), this function allows
users to set WDTimer overflow time from 32 s to 2 ms.
2. Enable the WDTimer counter to count down through the
function _7260_INT_Control(), this function allows WDT
function in the CPLD (as Figure 4.3) starting to count
down. After enabling the function, users must reload
WDTimter by step (1) before it overflows. This makes
PCI-7260 work normally under WDT monitoring. When it
overflows, CPLD interrupt will occurs and emergency
shutdown will be active too to make relay output in a
safety pattern unless user disable the emergency shut-
down function through function_7260_EMG_SETUP().
3. When WDTimer interrupt occurs, users must reload the
WDTimer through function
_7260_WDTimerSReload_Config() to clear WDTimer
carry out, and then clear the system interrupt through
function _7260_CLR_IRQ(). After doing this, the
WDTimer will count again unless user disable WDTimer
counter.