ProSoft Technology WRC-CANX - Manual (Page 21)

Western Reserve Controls WRC-CANX-xx Series 4
PUB 14.1 User’s Manual
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5.1.4. Autobaud Operation
Autobaud is the method by which a device automatically determines the baud rate on the
DeviceNet network and sets it’s internal baud rate to match without the need for switches or software
configuration. The CANX supports autobaud.
Autobaud operation has the advantage of allowing a system implementer or designer to ignore the
operating baud rate when installing the CANX. The general practice is that when an I/O device is
autobaud, it does not transmit a DupMacID request message immediately upon power up. It waits for
another (fixed baud rate) device to send its DupMacID message in order use that message to determine
to which baud rate the network has been set.
Since the CANX is not a logical node on DeviceNet, it does not initiate any DeviceNet
communications. When both the A and B sides are set to autobaud, a valid message on either side will be
used to set the baud rate on both sides. In addition, that message is transmitted out the other side of the
network to the nodes there, from which they can establish their baud rates if in autobaud.
In the case where no device that initiates this DupMacID sequence, all the autobaud devices will
just wait for some valid message to be generated.
The CANX baud rate is set by setting SW1 switch positions before powering up the A side of the
CANX, as defined in Table 4-1.