Rockwell Automation 1747-L5xx SLC 500 Modular Hardware Style User Manual - Manual (Page 191)

Publication 1747-UM011G-EN-P - June 2008
Setting Up the DH-485 Network 191
Software Considerations
Software considerations include the configuration of the network and
the parameters that can be set to the specific requirements of the
network. The following are major configuration factors that have a
significant effect on network performance.
• Number of nodes on the network
• Addresses of those nodes
• Communication rate
• Maximum node address selection
• SLC 5/03, SLC 5/04, and SLC 5/05 processors only - token
hold factor
• Maximum number of communicating devices
The following sections explain network considerations and describe
ways to select parameters for optimum network performance (speed).
Number of Nodes
The number of nodes on the network directly affects the data transfer
time between nodes. Unnecessary nodes (such as a second
programming terminal that is not being used) slow the data transfer
rate. The maximum number of nodes on the network is 32.
Setting Node Addresses
The best network performance occurs when node addresses start at 0
and are assigned in sequential order. SLC 500 processors default to
node address 1. The node address is stored in the processor status file
(S:15L). Processors cannot be node 0. Also, initiators such as personal
computers should be assigned the lowest numbered addresses to
minimize the time required to initialize the network.
Setting Processor Communication Rate
The best network performance occurs at the highest communication
rate. All devices must be at the same communication rate. The
communication rate is stored in the processor status file (S:15H).