Allen-Bradley ControlLogix 1756-DH485, User Manual, Page: 36 / 110

Publication 1756-UM532A-EN-P - May 2006
3-4 Use Data Highway 485 Network
This figure shows an SLC controller sending a local message to Channel A on
the 1756-DH485 module. Because the controller slot for Channel A is
configured to 0, the message is forwarded to the ControlLogix controller in
slot 0.
SLC Controller Sending a Local Message to Channel A on the 1756-DH485 Module
Because a local DH-485 message has only enough address information to get
the message to a target node on the same DH-485 network, the 1756-DH485
module that receives this message cannot identify where to send the message.
The 1756-DH485 module uses the Controller Slot configuration parameter in
RSLinx software to send the message to the local controller.
Local DH-485 messaging does not require a populated routing table. Local
DH-485 messaging does require a default or applied controller slot for each
channel configured for a DH-485 network.
IMPORTANT
Local DH-485 Messaging can target only one ControlLogix
controller per DH-485 channel. The ControlLogix
controller must reside in the same chassis as the
1756-DH485 module receiving the message.
Refer to Remote DH-485 Messaging on page 3-5 for more
information.
ControlLogix Chassis
SLC 5/03 Controller
Channel A
1756-DH485 Module
44052
AIC Link Coupler
AIC+ Link Coupler