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Chapter 6
Starting the DPU
Startup States
Refer to this chapter to learn how to:
• Start a standalone DPU
• Start DPUs in a backup pair
• Replace a DPU in a backup pair
When a DPU is restarted, it senses the type of initialization being performed
and starts in one of the following two modes:
Cold
A Cold initialization occurs following a power outage if no
configuration information is available from before the outage.
This can occur if no battery power is available when the DPU is
powered down, or if a Cold start is demanded through the front
panel mode switches. Following a Cold start, the DPU will remain
in Offline state until it is manually placed online. Refer to
"Demanding a Cold Startup."
Cool
A Cool initialization occurs if configuration data is available in
flash memory, unless a Cold start is demanded through the front
panel mode switches. Following a Cool start, the DPU will
automatically progress to Online state unless its keyswitch is in
the Offline position.
In both modes, the DPU uses the time and date preserved in its CMOS clock,
then synchronizes with other stations on the DPU Bus. If the CMOS clock is
not valid, the DPU will raise an alarm and remain Offline until it receives
time via the DPU Bus.
When the DPU is reset or the 24 Vdc power to the DPU is interrupted, Event
Queue information is lost, but the internal battery allows the configuration to
be preserved in flash memory. When the DPU restarts, it reloads its
configuration and erases the flash memory to prevent the possibility of later
reloading an out of date configuration.
Metso Automation MAX Controls • • • • 277573 • • • •
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