Release Note
DeviceNet Communication Card Release Note
Catalog No. 1784-PCD
What’s in This Release Note?
This Release Note contains information about the 1784-PCD card, Series A, B, and
C.
Connecting to Multiple Networks - Do Not Rely on Autobaud
Use caution when using the Autobaud feature on multiple DeviceNet networks that
are operating at different baud rates. When a 1784-PCD card is connected to a
network, you cannot disconnect from that network and reconnect to another
DeviceNet network that is using a different baud rate. The card will not
automatically use the new network’s baud rate. The driver must be reconfigured
when you switch to a DeviceNet network operating at a different baud rate.
Whether or not Autobaud is in use, if messages are sent on the new network at an
incorrect baud rate, devices on that network could enter a Bus-off state (refer to the
DeviceNet Specification. You can purchase the specification from the Open
DeviceNet Vendor Association, Inc. Visit the ODVA website at www.odva.org). A
device can recover from a Bus-off condition by being reset or shut down and
restarted.
Publication 1784-RN531A-EN-P - July 2001
To properly switch between networks of different baud rates, reconfigure the
driver.
If you are using RSLinx:
1. Select Communications
⇒Configure ⇒Delete.
2. Select Communications
⇒Configure ⇒Add New.
TIP
Autobaud will not work if there is not sufficient traffic on the
network.
Using Auto-address After Network Power Loss
Because the 1784-PCD card will Auto-address again when power is lost and then
restored to a DeviceNet network, potentially causing a race condition, we
recommend that the Auto-address feature only be used when connecting to a
network for a short period of time. The Auto-address feature should not be used for
long-term monitoring applications.
For example, assume there is a device at address 62 but not at address 61. When
the 1784-PCD card is connected to the network and instructed to Auto-address, it
will first try address 62. Since a device exists at address 62, the PCD card will try
address 61. Since no device exists at address 61, the 1784-PCD card will go on-line
at address 61. If network power is then lost and restored, the 1784-PCD card will go
through its Auto-address procedure again, starting at address 62. However, the
device at address 62 may take longer to come on-line than the 1784-PCD. In this
case, the 1784-PCD card will go on-line at address 62. The device that was
originally at address 62 will not be able to come on-line since it will get a Duplicate
MAC ID error.
Publication 1784-RN531A-EN-P - July 2001
PN 957564-58
© 2001 Rockwell International Corporation. Printed in the U.S.A.