Modbus RTU using SLC 5/05

Hi,

I'm hoping to use an SLC 5/05 PLC to communicate as Modbus RTU Master to a number of Modbus TCP slaves. I understand that a gateway is required to switch protocols however the budget for the project is fairly limited as it is a college project.

My question is whether the SLC 5/05 would be able to implement Modbus RTU over the DF1 RS232 port, or would one of the Prosoft Modbus modules be required.

Also, assuming this would be possible, what type of gateway would be required. There seem to be a number of RTU to TCP gateways around but they're all RS485 to TCP and since the PLC only has an RS232 port i'm unsure how to proceed.

Thanks in advance.

mcmahobr said:

Hi,

I'm hoping to use an SLC 5/05 PLC to communicate as Modbus RTU Master to a number of Modbus TCP slaves. I understand that a gateway is required to switch protocols however the budget for the project is fairly limited as it is a college project.

My question is whether the SLC 5/05 would be able to implement Modbus RTU over the DF1 RS232 port, or would one of the Prosoft Modbus modules be required.

Also, assuming this would be possible, what type of gateway would be required. There seem to be a number of RTU to TCP gateways around but they're all RS485 to TCP and since the PLC only has an RS232 port i'm unsure how to proceed.

Thanks in advance.

Click to expand...

I would have imagined the easiest way to do this would be to add a Modbus TCP card to the PLC if such a thing i available (i don't used SLC)

A Schneider EGX150 will do Modbus RTU with RS232 on master side Modbus TCP on the slave side

https://www.schneider-electric.com/...t-gateway---2-ethernetport---24-v-dc-and-poe/

Or an Anybus may have something that will work

Hi and welcome to the Forum fellow Paddy!

mcmahobr said:

...My question is whether the SLC 5/05 would be able to implement Modbus RTU over the DF1 RS232 port...

Click to expand...

If you can read the following Rockwell Automation Knowledgebase technote article: -

58253 - SLC Processors that Support Modbus Protocol
Access Level: Everyone

There you will see that support for Modbus RTU Master capabilities on the SLC modular controllers, including the 5/05, using the Channel 0 RS-232 serial port, was added at firmware revision "OS 501 Series C FRN 11", which was released about 10 years ago.

You must also be using RSLogix 500 v8.1 or later to support the selection of Modbus RTU Master for the Channel 0 serial port.

Do you have the controller or know what firmware series and revision it's currently at?

The latest is "OS501 Series C FRN 13" (released 2016) and if you need it then you can download it from here...

FIND DOWNLOADS

Type "SLC 5/05" in the search field.

Any further question fire away.

Regards,
George

Its a series C 5/05 with the frn 7 firmware, i got the download for the latest firmware but haven't gotten around to flashing it yet. I can configure the Rs232 port for Modbus in RsLogix too so i'd say that's fine.

Knowing that'll work fine with the RS232 port will certainly save a lot of heartache as far as my budget is concerned anyway. I've had a look since for specifically Rs232 to TCP gateways and there's plenty of affordable options on ebay.

Thanks for the replies, that's cleared a lot up!

Regards,
Brian.