Rockwell Automation 1756-DHRIO_DHRIOXT ControlLogix Data Highway Plus-Remote I/O Communication Interface Module - Manual (Page 107)

Rockwell Automation Publication 1756-UM514C-EN-P - June 2014 107
Using the 1756-DHRIO and 1756-DHRIOXT Modules in Remote I/O Applications Chapter 9
Adapter Module I/O The 1756-DHRIO and 1756-DHRIOXT modules scan the remote I/O devices
as they appear in the ControlLogix controller’s controller organizer. The entries
in the organizer represent logical adapters. The physical adapter modules on
remote I/O can act as several racks. This depends on the addressing mode of the
physical adapter and chassis. The Studio 5000 environment enables four choices
for the adapter modules:
• 1747 Remote I/O adapter
• 1771 Remote I/O adapter
• 1794 Remote I/O adapter
• Generic Remote I/O adapter
Each entry includes the following:
• rack address - values are 00-77 octal
• starting group - can start in slot 0, 2, 4, or 6
• rack size - can be 1/4, 1/2, 3/4 or full rack
The 1756-DHRIO and 1756-DHRIOXT modules consume the adapter output
data sent by the ControlLogix controller on the connection created when you
add remote I/O devices in the Studio 5000 environment.
The owner-controller produces the output data at the RPI; this output data
production is not tied to the scan time of the controller’s program. The remote
I/O scanner sends output data to the remote I/O adapters at a rate dependent on
the number of adapters on the channel and the baud rate used.
The 1756-DHRIO and 1756-DHRIOXT modules produce the rack input data
received in the adapter response immediately after the remote I/O adapter
response is received. The owner-controller receives the data directly into the data
buffer created by the software. The frequency at which the input data is produced
depends upon the number of adapters on the channel and the baud rate used.
IMPORTANT Each choice determines what type of adapter is present on the remote I/O
network. However, they all behave the same in the ControlLogix system.
When online, the 1756-DHRIO and 1756-DHRIOXT modules cannot tell
which adapter is connected to the remote I/O network.