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Connecting an Ethernet raw ASCII device to EtherNet/IP

How logical!

– Joe House

Comtrol’s DeviceMaster® UP is most commonly associated with connecting serial devices to industrial protocols such as EtherNet/IP.  This common association tells less than half of the DeviceMaster UP’s capabilities in EtherNet/IP. The DeviceMaster UP is also capable of connecting ASCII over Ethernet devices to EtherNet/IP – something that is only logical.

A single DeviceMaster UP 1-Port is capable of supporting one serial connection AND one logical, TCP socket connection simultaneously.  By supporting both connections simultaneously, a DeviceMaster UP 1-Port can connect two devices to a PLC.

ASCII - Ethernet port splitterIf the DeviceMaster UP only has one Ethernet port – how can you connect two things into a single port?

The DeviceMaster UP supports ASCII over Ethernet connections through a logical TCP socket connection, something that only requires the DeviceMaster UP, Ethernet device, and PLC be on the same network.  Put in different terms – the DeviceMaster UP, Ethernet device, and PLC must all be able to communicate via TCP/IP addressing.

There are certainly many ways to put three products on the same network. The easiest, however, is to connect all three products to one of Comtrol’s RocketLinx Ethernet switches such as the ES8105.  This method is shown below.  Please note the black lines illustrate physical connections via copper Ethernet cables while the dotted red line represents a logical connection between the Ethernet device (printer) and the PLC.  This is the intended target for data transmission.

DeviceMaster Ethernet to EtherNet/IP


As the number of Ethernet connected devices continues to increase in the industrial market space, it is foolish to expect them all to behave the same.  Some devices, such as a bar code scanner may just send ASCII data without command from the PLC.  Anytime a new bar code is read it is automatically packetized and sent.  Other devices, like a printer, may demand a prompt from the PLC to send data. The PLC says, “print this,” and the printer prints and reports back, “Done.”

Clearly this is an oversimplification but it does lead to a valid point.  To truly provide a flexible connection to EtherNet/IP when communicating with ASCII over Ethernet devices, the DeviceMaster UP must be able to work with both devices that simply send data and those that demand a prompt to send data.  In context of establishing connections, the DeviceMaster UP is capable of operating as either a client or server.  In other words, the DeviceMaster UP can be set to listen for a connection – or to initiate one.

Either way, the DeviceMaster UP can be configured easily through the web interface under the “Configure Ethernet Device” heading.  For a bar code scanner, a customer may select the DeviceMaster UP to be configured as a client; a client simply listens to the ASCII over Ethernet data from the scanner and sends it on to the PLC after converting to EtherNet/IP.  In the above printing application, the DeviceMaster UP may operate as a server – receiving commands from the PLC in EtherNet/IP and passing them onto the printer in TCP/IP.  Whichever way your application demands you will be greeted by the below page:

DeviceMaster UP

After entering all appropriate system information, the DeviceMaster UP can make your intended connection – from an Ethernet device to EtherNet/IP.  In the end it is the DeviceMaster’s flexibility that makes it a valuable product, whether converting serial to EtherNet/IP, or Ethernet (TCP/IP) to EtherNet/IP, the Comtrol DeviceMaster UP is the ticket – either way it’s only logical!


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