Hitachi HF-W6500 60 Manual page 110

6. LIBRARY FUNCTIONS
(2) Behavior of the WDTTO contact of the RAS external contacts interface
This sub-subsection describes the behavior of the WDTTO contact of the RAS external
contacts interface under each of the following conditions.
● When the equipment starts
The WDTTO contact is closed.
● When the OS starts
The WDTTO contact is closed when the OS starts. The WDTTO contact becomes open
when the watchdog timer is retriggered by the automatic retriggering feature for watchdog
timer or the WdtControl function.
● When the WdtContol function is called
If dwCmd is WDT_SET:
The WDTTO contact becomes open. If the watchdog timer is not retriggered afterward
within the specified timeout period, the contact becomes closed. If the watchdog timer is
retriggered when the contact is closed, the WDTTO contact becomes open.
If dwCmd is WDT_STOP:
The WDTTO contact becomes closed.
● When the automatic retriggering feature for watchdog timer is used
The WDTTO contact becomes open. The process for this function runs at the lowest
priority (idle priority class). If the amount of CPU time used by processes with a priority
higher than the idle priority class exceeds the set value, the watchdog timer times out.
And the contact becomes closed. Afterward, when free CPU time becomes available and
the process for this function can run, the watchdog timer resumes being retriggered and
the WDTTO contact becomes open.
Figure 6-1 shows an example of the behavior of the WDTTO contact when an application
controls the watchdog timer using the WdtControl function. In this example, the timeout of
the watchdog timer specified by the WdtControl function is 10 seconds.
6-6