Difference between RS485 & Modbus Protocol

[ArifAhmadpk]

Dear Members,

I have a RS485 TO Ethernet converter. With the help of this converter, i want to take data from device which have RS485 port (modbus RTU) and display the data on winccFlexible (Siemens SCADA Software) through Ethernet port. My question is, can i use any type of RS485 to Ethernet converter, or special kind of RS485 to Ethernet converter for Modbus protocol.


Best Regards,

Arif Ahmad

 

[wade_hassler]

RS485 is hardware serial-interface standard that defines the hardware for carrying a message.
Modbus is a messaging protocol that defines the content of that message.
So far, so good: the two do not 'differ' at all. BUT, there is one hardware requirement for Modbus over a SERIAL-line: the message ends when no character has been sent for 3.5(?) character-times.
That requirement is meaningless for Ethernet because a message 'ends' when its packet ends.

Another potential problem is that Modbus defines a CRC for its messages and Ethernet already has a CRC on its packets.

You need to know how your converter works: how it knows when an output-packet starts and when it ends.

 

[FvM]

I guess winccFlexible neither supports generic RS485 nor MODBUS transported over Ethernet. It rather works with OPC, PROFINET
or some SIMATIC low level protocols. But I'm not familiar with the last years new developments of the product.