We currently only support Rockford PLC's directly. I am not really familiar with the Siemens PLC, but if you are able to make a TCP connection through it, the printer will accept simple TCP connections over port 9100. You will need to send the printer specific commands to control it in this way: ZPL Programming Guidehttps://www.zebra.com/content/dam/zebra/manuals/printers/common/programming/zpl-zbi2-pm-en.pdf
I'm not sure this answers your question. Please let us know. I am also tagging this question to get one of our PLC experts to take a look.