SLC505 to read TCP/IP Device


Thread Starter


I have a device currently connected to my SLC 505 serially. I'd like to remove that device, plug it into a serial to Ethernet converter, and read that device over the Ethernet network. Does anyone have any experience? I know I can read another SLC505 with a message box over the network.

Lynn August Linse

Unfortunately, nearly all PLC with Ethernet only support their own protocol access to TCP/IP. One would think what you want is nearly a no-brainer - the PLC already has all the tools to manage a raw/ASCII device by serial port - why not just aim those tools at a raw TCP socket? Unfortunately, this is classified "too sensible to be true".

Your options will be:

1) Use 2 Enet-to-Serial converters to tunnel the remote device to your local serial port - not really a cost-effective way, but very doable by dozens of vendors products (including many from my own employer).

2) A number of companies offer the ability to pack/unpack ASCII messages from ENet protocols into register-like memory. This seems odd, but is an effective work-around for the PLC limitation. You'd use ladder logic to write an ASCII message into some registers, use a MSG block to write this data as-if to another SLC505 or CIF device. But the remote device is NOT a PLC, and smartly unpacks the data & sends it out the serial port. Any serial response is repacked to register-like memory, and another MSG block on the 5/05 can copy the response back to the PLC memory, where some tools need to parse the ASCII response. I'd get in trouble if I told you who makes these, but they DO exist, so look around.

3) A few of the PLC vendors or 3rd party do OFFER 2ndary Ethernet modules with raw access by custom user-written downloads - this means you'll end up with 2 UTP cables and have 2 IP - the native one for protocol access, and a raw one for some custom firmware.

Best solution would be for PLC vendors to modify their serial in/out modules to also support raw TCP sockets - but don't hold your breath waiting no matter how obvious this solution is.

Best regards

Lynn August Linse, [email protected] IA Firmware Specialist, Digi Int'l ( 26741 Portola Pkwy, Suite 1E #242 Foothill Ranch CA 92610-1743 USA
Not allowed.

While the SLC5/05 does conform to TCP/IP networking protocol, the application layer of the network stack is kept top-secret. In other words, a 5/05 will co-exist on a standard ethernet network, it just won't talk to anything else on the network except other AB products, or products from vendors that have paid the AB licensing fee.

I am not aware of any serial to ethernet adapters that have been 'blessed' with the blue stop sign, but I haven't been looking at AB gear much anymore, so something might be out there....

--Joe Jansen
AB has a Ethernet Interface 1761-NET-ENI Module.
This module provides Ethernet connection to Micrologix controllers and other DF1 full-duplex devices. I know this module allows a SLC5/03 connected to its DF1 serial port to communicate over Ethernet. If this will work for your application, I can't answer. You may want to talk to your AB supplier. The downside is that the module is not cheap.