Logix Block Module Operation; Logix Block Modules Connected Through Ethernet/Ip Network; (1757-Ffld Linking Device) - Allen-Bradley 9308-RSFB64ENE User Manual

Logix Block Module
Operation
Logix Block Modules
Connected through
EtherNet/IP Network

(1757-FFLD linking device)

• If the configuration data is not appropriate, the data is rejected and an error
message is displayed in the software. In this case, the configuration data can
be inappropriate for any of a number of reasons. For example, a module's
configuration data may be appropriate except for a mismatch in electronic
keying that prevents normal operation.
The controller maintains and monitors its connection with a module. Any break
in the connection, such as removing power from the linking device, causes the
controller to set fault status bits in the data area associated with the module. You
can use ladder logic to monitor this data area and detect module failures.
In the ControlLogix system, the owner-controller does not poll Logix Block
modules after a connection is established. The modules multicast their data
periodically. Multicast frequency depends on the options chosen during
configuration and where in the control system that the Logix Block module
resides.
Because a Logix Block module resides in the linking device, which acts like a
remote chassis, the role of a requested packet interval (RPI) varies slightly with
respect to getting data to the owner-controller, depending on what network type
you are using to connect to the Logix Block module.
We recommend that you set the value of your RPI to half of your
macrocycle value.
When Logix Block modules are connected to the owner-controller through an
EtherNet/IP network, data is sent over the network through the Ethernet port on
the 1757-FFLD linking device to the owner-controller as long as it has not sent
data within a time frame that is 1/4 the value of the Logix Block module's RPI.
For example, if a Logix Block module uses an RPI = 100 ms, the 1757-FFLD
linking device will only send module data immediately on receiving it if another
data packet was not sent within the last 25 ms.
The Ethernet module will either multicast the module's data to all devices on the
network or unicast to a specific owner-controller depending on the setting of the
Unicast checkbox on the Connection tab of the Module Properties dialog box.
Rockwell Automation Publication 1757-UM012A-EN-P - July 2011
Logix Block Operation in a ControlLogix System Chapter 6
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