Serial Watchdog
12
After the computer has finished its startup procedure, the watchdog
program sends the START-command to the watchdog. Now the
watchdog is reactivated. It sets the COMMUNICATION-LED and the
STATE-OF-HEALTH-LED flushes red. The watchdog waits 30 seconds
for a PING-command. If it receives a ping, it clears all timers and starts
waiting again, independent of the parameter. If the ping does not appear
within 30 seconds, the watchdog generates a periodical acoustic signal,
if audible alarm is enabled, which indicates that the power relay will be
opened in 5 minutes and sets the STATE-OF-HEALTH-LED to red. This
process can be stopped by sending the STOP-command.
If the watchdog receives a ping during this phase, it sets the STATE-
OF-HEALTH-LED and the acoustic signal according to table 1 and
clears all timers. Now it waits exactly 30 seconds for the next ping (see
above).
If no ping is received within 5 minutes after the STATE-OF-HEALTH-
LED has changed to red, the watchdog generates a continuous acoustic
signal (if enabled) and opens the power relay for exactly 40s. During this
time it does not accept any commands. After these 40 seconds the
watchdog runs its initialization procedure as described above.
The STOP-command works everytime unless the power relay is open. It
clears the COMMUNICATION-LED, sets the STATE-OF-HEALTH-LED
to red and disables all timers including the 1H-timer. Only the next
START-command will activate the watchdog again.
Table 1:
Watchdog behaviour on different commands
Command Parameter STATE-OF-HEALTH-LED
acoustic signal
(1
START
xxh
red flushing
off
STOP
xxh
red
off
PING
00h
green
off
PING
01h
red flushing
off
PING
02h
red
5 sec. every hour
(1
if enabled