Allen-Bradley micrologix 1500, Руководство пользователя

Страница: 117 / 149

Publication 1764-UM001A-US-P
Understanding Communication Protocols E-13
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
•
baud rate
The following sections explain network considerations and describe ways to select
parameters for optimum network performance (speed). See your programming
software’s user manual for more information.
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 are assigned in
sequential order. Initiators, such as personal computers, should be assigned the
lowest numbered addresses to minimize the time required to initialize the network.
The valid range for the MicroLogix 1500 controllers is 1-31 (controllers cannot be
node 0). The default setting is 1. The node address is stored in the controller
Communications Status file (CS0:5/0 to CS0:5/7).
Setting Controller Baud Rate
The best network performance occurs at the highest baud rate, which is 19200.
This is the default baud rate for a MicroLogix 1500 device on the DH-485
network. All devices must be at the same baud rate. This rate is stored in the
controller Communications Status file (CS0:5/8 to CS0:5/15).
Setting Maximum Node Address
Once you have an established network set up and are confident that you will not be
adding more devices, you may enhance performance by adjusting the maximum
node address of your controllers. It should be set to the highest node address being
used.
IMPORTANT
All devices should be set to the same maximum node address.
AB Spares