Rockwell Automation 1747-L5xx SLC 500 Modular Hardware Style User Manual - Manual (Page 192)

Publication 1747-UM011G-EN-P - June 2008
192 Setting Up the DH-485 Network
Maximum Node Address Setting
The maximum node address parameter should be set as low as
possible. This minimizes the amount of time used in soliciting
successors when initializing the network. If all nodes are addressed in
sequence from 0, and the maximum node address is equal to the
address of the highest addressed node, the token rotation will
improve by the amount of time required to transmit a solicit successor
packet plus the slot timeout value.
Note that this does not allow any node to be added to the network
without affecting the response time. On the other hand, since the time
required to hold an open station address is greater than the time
required to pass a token, it can be useful to leave a temporary device
(such as a personal computer) connected if there is only one such
device. (A solicit successor packet requires the same transmission time
as the token pass, but there is an added slot timeout period.)
See your programming software user manual for the procedures to set
node addresses, processor communication rate, and maximum node
addresses.
Maximum Number of Communicating Devices
SLC 500 fixed and SLC 5/01 processors can be selected by two
initiators maximum at the same time. Using more than two initiators to
select the same SLC 500 fixed and SLC 5/01 processors at the same
time can cause communication timeouts.
IMPORTANT
The SLC 500 series A (only) processors set the maximum node
address to 31 when power is cycled increasing initialization and
response time of the network.