Allen-Bradley 1794-IE8H, User Manual, Page: 18 / 146

Publication 1794-UM063A-EN-P - March 2006
1-2 About the FLEX I/O HART Analog Modules
How FLEX I/O Analog
Modules
Communicate with
Programmable Controllers
FLEX I/O analog modules provide best utility when used with ControlNet
products on the ControlNet network. Data connections are established
between the I/O module and an Allen-Bradley programmable controller
(PLC) to transfer information between the two at a scheduled rate.
Input module information is then automatically made available in the PLC
data table through the data connection. Reciprocally, output data information
determined by the PLC program is also automatically transferred from the
PLC data table to the output module through the data connection.
In addition, when the data connection is originally established, configuration
information for the module is automatically transferred to it via the network.
Events Following Power-up
You must apply +24V dc power to your FLEX I/O analog I/O modules. The
following sequence of events occurs after power has initially been applied to
your module:
1. The module begins an internal diagnostic check. The channel 0 indicator
turns ON to indicate the check has begun. The indicator turns OFF
when the check is finished.
2. After the diagnostic check, module configuration information, selected
by the user and downloaded over the network, is applied by the module.
For more information on configuration options, see Chapter 2.
3. Following the module configuration download for the 1794-IE8H
module, the module begins producing runtime data for the PLC
processor.
Following the module configuration download for the 1794-OE8H
module, the module applies configuration data to output channels.
4. If any diagnostics or alarms are generated during normal module
operation, the data is returned to the PLC processor.