Rockwell Automation 1756-DHRIO_DHRIOXT ControlLogix Data Highway Plus-Remote I/O Communication Interface Module - Manual (Page 105)

Rockwell Automation Publication 1756-UM514C-EN-P - June 2014 105
Using the 1756-DHRIO and 1756-DHRIOXT Modules in Remote I/O Applications Chapter 9
Exchange I/O Data Between the Module and Adapters
I/O data is exchanged between the 1756-DHRIO or 1756-DHRIOXT module
and adapters on the remote I/O link based on a list of adapters generated in the
Studio 5000 environment.
The ControlLogix controller, as the 1756-DHRIO or1756-DHRIOXT
module’s owner-controller, downloads this list, along with the remote I/O baud
rate, to the 1756-DHRIO or1756-DHRIOXT module. The 1756-DHRIO or
1756-DHRIOXT module scans each adapter (exchange I/O data) in the list in a
round-robin fashion.
Exchange I/O Data Between the Module and the ControlLogix
Controller
I/O data and status are exchanged between the 1756-DHRIO or
1756-DHRIOXT module and the ControlLogix controller through the
producer/consumer model used by the ControlLogix system.
Multiple connections are established between the 1756-DHRIO or
1756-DHRIOXT module and the ControlLogix controller. These connections
can be classified in two categories. In the first category, connections are
established between the 1756-DHRIO or 1756-DHRIOXT module and the
ControlLogix controller for each adapter on the remote I/O link. I/O data is
exchanged on these connections.
In the second category, a connection is established between the supervisor of the
remote I/O on the 1756-DHRIO or 1756-DHRIOXT module (the supervisor
is the internal remote I/O scanner on the module) and the ControlLogix
controller. Remote I/O scanner status is exchanged on this connection. In this
case, the data exchange is bidirectional. The 1756-DHRIO or 1756-DHRIOXT
module reports status on the remote I/O scanner, and the ControlLogix
controller maintains ownership of the 1756-DHRIO or1756-DHRIOXT
module.
I/O Configuration Tree in Studio 5000 Environment Controller
Organizer
The I/O configuration tree in the Studio 5000 environment Controller
Organizer specifies the connections to the 1756-DHRIO or 1756-DHRIOXT
module and generates the adapter list of the 1756-DHRIO or 1756-DHRIOXT
modules to scan.
IMPORTANT Only one ControlLogix controller can communicate with and own the
remote I/O channels on a 1756-DHRIO or 1756-DHRIOXT module.