Filter
Top Products
235
Appendix B
DeviceNet Connections
DeviceNet has several different protocols for remote I/O communications between Master and Slave devices.
Connections are units used to monitor those protocols.
There are four kinds of DeviceNet remote I/O communications protocols (connections): Poll, bit–strobe, COS
(change of state), and cyclic. CS/CJ-series DeviceNet Units support all four types.
The connection used by the DeviceNet Unit is automatically selected if the Configurator is not used.
If the Configurator is used, the connection can be automatically selected by the DeviceNet Unit or the user can
specify the connections for each slave. Up to two connections can be set. COS and cyclic connections cannot
be specified at the same time. The characteristics of each connection are outlined in the following table.
Note 1. The C200HW-DRM21-V1 and CVM1-DRM21-V1 DeviceNet Master Units use bit-strobe connections
with slaves with 8 or less input points and poll connections with other slaves. The DeviceNet Unit au-
tomatically chooses the connection.
2. There can be only one master on each network if COS or cyclic connections are used.
Connection Characteristics
Poll Used for basic I/O.
Bit-strobe Used for input of 8 bytes or less. Sends broadcasting requests from master and receives input
from slaves.
COS (Change of
State)
Communications occur at regular cycles (heartbeat timer) and the con-
nection is determined by the master or slave sending the data.
Data can be sent only when required, which reduces the network com-
munications load.
This connection can be used to send data to the master or slave if the
master or slave data changes. For DeviceNet Units, the transmission
timing can be decided in the user program.
The following points apply for CS/CJ-series DeviceNet Units:
If the Master COS Send Switch is turned ON, remote I/O communica-
tions output data can be sent every time from the master using COS to
the slaves that support COS.
If the Slave COS Send Switch is turned ON, remote I/O communications
output data can be sent every time from the slave using COS to the
master (input data from the perspective of the master).
Even if the software switch is not turned ON, the COS communications
using regular cycles (heartbeat timer) can be performed simultaneously.
Note: This CS/CJ-series DeviceNet Unit is the only OMRON slave that
supports COS.
Note: COS and cyclic
connections cannot be
used at the same time.
Cyclic Communications timing is determined by regular cycles (heartbeat
timer).
Masters and slaves send output or input data in regular cycles.