Rockwell Automation 1784-KTXD User Manual download pdf (Page 193)

Publication 1747-UM011F-EN-P - May 2007

Setting Up the DH-485 Network 193

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).

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Rockwell Automation 1784-KTXD User Manual Page 193