Figure 6-1 Behavior Of The Wdtto Contact; Figure 6-2 Behavior Of The Wdtto Contact (When The Os Shuts Down) - Hitachi HF-W7500 40 Manual

WDT is retriggered.
WdtControl function is called.
Power is
(Timeout: 10 seconds)
turned on.
Contact open
(Normal)
Contact closed
(WDT has timed out.)
OS startup
Dotted lines in Figure 6-1 denote the respective states of the contact and the thick line denotes
the transition of the state of the contact.
Figure 6-2 shows an example of the behavior of the WDTTO contact when the OS shuts
down. In this example, the timeout of the watchdog timer is 60 seconds. The process that
retriggers the watchdog timer terminates during shutdown and consequently the watchdog
timer times out.
WDT is retriggered.
Contact open
(Normal)
Contact closed
(WDT has timed out.)
WDT is
retriggered.

Figure 6-2 Behavior of the WDTTO Contact (When the OS Shuts Down)

Dotted lines in Figure 6-2 denote the respective states of the contact and the thick line denotes
the transition of the state of the contact.
NOTE
In the explanation above, it is assumed that the RAS external contacts interface
is HJ-7805-21. If you use HJ-7805-22 as a RAS external contacts interface, the
behavior of the contact is opposite. This contact is open when the contact in the
explanation above is closed and the other way around.
WDT times out.
10 seconds
WDT is
retriggered.
WDT is retriggered.

Figure 6-1 Behavior of the WDTTO Contact

OS shutdown starts. WDT times out.
60 seconds
WDT is retriggered.
WDT stops.
WdtControl function is called.
6-7
6. LIBRARY FUNCTIONS
Power is turned off.
WDT has stopped.
Time →
Power is turned off.
Time →