Watlow Electric Gateway & DeviceNet - Manual (Page 7)

RUI/Gateway & DeviceNet TM
Configuration & Ladder Logic Example
Using an Allen-Bradley CompactLogix PLC
Watlow
1241 Bundy Blvd
Winona, MN 55987
Telephone: 507-494-5656
© 2007 Watlow Electric Mfg Co 7
4/08
14. After the scanner recognizes the RUI/Gateway on the network it will then appear as an
Available Device as shown below. Before clicking on the right arrow to add it in the scanners
scan list consider the effect of the Automap on Add check box. If this box is checked and
there are other currently existing nodes on the network where they may not be using
complete words (less than 32 bits) the scanner will not consider word boundaries when
adding a new node and will attempt to utilize every available bit in the PLC. As an example, if
a given device has only 9 bytes of information it will use 2¼ 32 bit words (3 bytes not used in
the last word). Now, when adding a new node like the RU/Gateway that utilizes 80 bytes (20-
32 bit words with each being a separate entity, i.e., 32 bit Set Point) ¾ of the first word will be
placed in the last word of the node mentioned above. The impact of this action would then
break up all of the 20 words sent to and received from the RUI/Gateway in a convoluted way.
For this reason, it is suggested that this box be unchecked (if there are other devices on the
network) allowing the individual doing the configuration to select the appropriate word
boundaries manually.
In this case, there are no other devices on the network so leaving the Automap on Add box
checked will not have a negative impact on the gateway configuration.