An input of one module can be linked to the output registers of another
module only if they are of the same register class. For more on module
linking, see the section on

Register Classes

later in this chapter.

The ‘Not Available’ V alue

If a module is not linked to anything, its output registers will not contain any
values and are set to Not Available. In addition, if a module has an input that
is invalid, its output register is also set to Not Available. This helps
distinguish between cases where a register contains a value like ’0’ (zero) or
Off, and cases where there is actually no value available.
If the inputs of a module are Not Available, its output registers are also Not
Available. The setting of Not Available propagates through linked modules.

Online and Offline Modules

The terms online and offline describe whether a module is currently active
or not. A module is described as online when it is functioning normally
(monitoring its input and updating its output registers). An offline module is
inactive.
When you configure a 9000 series meter, the affected modules are
temporarily taken offline while they are programmed with your changes.
Once they have been programmed, the modules are then placed back
online. When a module is created, the module is offline. To make it online,
you may link the module to other modules and/or configure setup registers
properly.
Normally, this is a routine procedure; however, certain circumstances may
prevent a module from returning online. For example, if the node lacks suffi-
cient processing power to operate the module, or if the module has been
configured incorrectly, the module will remain offline.
Making Configuration Changes
When you make configuration changes to a 9000 series device, you are
either changing a value in a module’s setup register or you are changing the
linkage between two or more modules. The types of configuration changes
discussed in this chapter are changes to the settings held in module setup
registers.
Changing the settings in a module’s setup registers changes the way the
device operates. Carefully consider any change you intend to make before
proceeding. Adding or deleting links between modules significantly alters
the operation of the device, and should only be performed by experienced
personnel.
The 9000 series meter is factory-configured for use in most standard
applications. Aside from basic setup, you do not need to make any
modifications to the device’s configuration for normal use. The following
sections address advanced configuration.