Rockwell Automation 1753-DNSI DeviceNet Safety Scanner for GuardPLC Controllers - Manual (Page 19)

Publication 1753-UM002A-EN-P - July 2005
Before You Begin 1-9
Choose a Communication Rate for the Network
The default communication rate for a DeviceNet network is
125K bit/s. This is the easiest communication rate to use.
If you choose to use a different communication rate, the length of the
trunkline and type of cable determine which communication rates
your application can support.
Set the baud rate of the DeviceNet Safety Scanner using the Node
Commissioning tool in RSNetWorx for DeviceNet. See Commission All
Nodes on page 3-2.
The following table lists the most common methods for setting
communication rates for other DeviceNet devices.
Communication
Rate
Maximum Distance
Cumulative Drop
Line Length
flat cable thick cable thin cable
125K bit/s 420 m (1378 ft) 500 m (1640 ft) 100 m (328 ft) 156 m (512 ft)
250K bit/s 200 m (656 ft) 250 m (820 ft) 100 m (328 ft) 78 m (256 ft)
500K bit/s 75 m (246 ft) 100 m (328 ft) 100 m (328 ft) 39 m (128 ft)
IMPORTANT
If you change the communication rate of your
network, make sure that all devices change to the
new communication rate. Mixed communication
rates produce communication errors.
Method Description
autobaud At power up, the device automatically sets its communication
rate to the baud rate of the first device it finds on the network.
The device remains set until it powers up again.
The network requires at least one device with a fixed
communication rate so that the autobaud devices have something
against which to set. Typically, scanners and network interfaces
have a fixed communication rate.
switches or
pushbuttons on the
device Some devices have switches or a pushbutton that sets the
communication rate. Typically, the switch or pushbutton lets you
select either autobaud or a fixed communication rate (125K, 250K,
or 500K bit/s). The device reads the switch setting at power up. If
you change the setting, you must cycle power for the change to
take effect.
software Some devices require a programming device to set its address
and communication rate. For example, you can use the Node
Commissioning tool in RSNetWorx for DeviceNet to set the
communication rate of a device.