Rockwell Automation DeviceNet Communications Module - Manual (Page 76)

8-2 DeviceNet Communications Module
Benefits of Multi-Drive mode include:
• Lower hardware costs. Only one MDCOMM-DNET module is
needed for up to five drives. MD60 drives can also be used for the
daisy-chained drives instead of MD65 drives.
• Reduces the network node count (DeviceNet is 63 nodes
maximum). For example, in Single-Drive mode 30 drives would
consume 30 nodes. In Multi-Drive mode, 30 drives can be
connected in 6 nodes.
• Provides a means to put MD60 drives on DeviceNet (MD60
drives do not have an internal communications module slot).
• Controller can control, monitor, and read/write parameters for all
five drives.
The trade-offs of Multi-Drive mode include:
• If the MD65 drive with the MDCOMM-DNET module is powered
down, then communications with the daisy-chained drives are
disrupted, and the drives will take the appropriate
communications loss action set in each drive.
• Communications throughput to the daisy-chained drives will be
slower than if each drive was a separate node on DeviceNet
(Single-Drive mode). This is because the MDCOMM-DNET
module must take the DeviceNet data for the other drives and
sequentially send the respective data to each drive over RS-485.
The approximate additional throughput time for Logic
Command/Reference to be transmitted and received by each
drive is shown in table 8.1.
Figure 8.2 – Example of a Multi-Drive Mode Network
DeviceNet
up to 5 drives per node
MD65 Drive
MDCOMM-DNET
Up to 4 MD65 or MD60 Drives
AK-U0-RJ45-TB2P
Connector w/3rd Party
Terminating Resistor
AK-U0-RJ45-TB2P
Connector w/3rd Party
Terminating Resistor
AK-U0-RJ45-TB2P RS-485