Rockwell Automation RECOMM-ENET EtherNet/IP Communications Module - Manual (Page 182)

Glossary-4 EtherNet/IP Communications Module
The number of devices on your EtherNet/IP network will vary
depending on the number of bytes that are used for the network
address. In many cases you are given a network with a Class C
address, in which the first three bytes contain the network address
(subnet mask = 255.255.255.0). This leaves 8 bits or 256
addresses on your network. Because two addresses are reserved
for special uses (0 is an address for the network usually used by the
router, and 255 is an address for broadcast messages to all network
devices), you have 254 addresses to use on a Class C address
block.
To ensure that each device on the Internet has a unique address,
contact your network administrator or Internet Service Provider for
unique fixed IP addresses. You can then set the unique IP address
for the module by using a BOOTP server or by manually configuring
parameters in the module. The module reads the values of these
parameters only at power up.
Logic Command/Logic Status - The Logic Command is used to
control the SP600 drive (e.g., start, stop, direction). It consists of
one 16-bit word of input to the module from the network. The
definitions of the bits in this word depend on the drive.
The Logic Status is used to monitor the SP600 drive (for example,
operating state, motor direction). It consists of one 16-bit word of
output from the module to the network. The definitions of the bits in
this word depend on the drive.
Master-Slave hierarchy - A module configured for a Master-Slave
hierarch exchanges data with the master device. Usually, a network
has one scanner, which is the master device, and all other devices
are slave devices (for example, drives connected to Ethernet/IP
modules).
0 1 7 15 23 31
Class A 0 Network ID Host ID
0 1 7 15 23 31
Class B 1 0 Network ID Host ID
0 1 2 7 15 23 31
Class C 1 1 0 Network ID Host ID