1756 Devicenet problem

Hi all.

I have a controllogix 5561 with a 1756-DNB devicenet scanner in the backplane. The scanner is a master for three E3Plus relays.

problem is that the scanner won't go into run mode. i set the CommandRegister.Run bit high, but StatusRegister.Run stays low. Only clue i have is that StatusRegister.DeviceFailure is high.

any ideas?

A 1756-DNB module connected to a valid network should definitely go into RUN mode when it is commanded to do so.

First check the 1756-DNB entry in the I/O tree to be sure there's no connection fault indication. The Connection tab for the module configuration should also indicate it's in a Running mode.

Describe the numbers and letters that are scrolling across the scanner module's display.

Thanks for the tips, was a keying mismatch problem - sorted out now.

i have another question though, what is the best method to make tag values and alarm conditions available across an ethernet connection (provided by a 1756 ENBT module) to other plc devices on the network?

The most efficient way to share data between ControlLogix controllers across an Ethernet network is to use Produced/Consumed Tags. These use the same mechanisms as EtherNet/IP I/O connections to transmit and receive Tag value data expressed as individual Tags, as arrays, or as UDT's. All the connection handling and timing is performed behind the scenes by the controller and the Ethernet modules, so you don't have to program or manage Message instructions.

You do need a properly designed Ethernet network to make this an effective mechanism, though. Start by obtaining the following publications from Rockwell Automation:

EtherNet/IP Performance and Application Guide publication ENET-AP001

EtherNet/IP Media Planning and Installation Guide publication ENET-IN001

EtherNet/IP Modules in Logix 5000 Control Systems User Manual publication ENET-UM001

thankyou. i thought that might be the answer, but i will certainly have a look at the publications you reccomended.