What are the differences between different versions of RS485?

Question

I'm trying to find out the best order an RS485 interface as an optional interface for my CX2033 Beckhoff industrial PC. in the ordering page I faced the following four details of RS485 with some strange expressions:

drop/end point

with/without echo

termination on/off

RS485 interface, D-sub socket, 9-pin, configuration as an end point, without echo, termination on
RS485 interface, D-sub socket, 9-pin, configuration as an end point, with echo, termination on
RS485 interface, D-sub socket, 9-pin, configuration as drop point, without echo, termination off
RS485 interface, D-sub socket, 9-pin, configuration as drop point, with echo, termination off

I looked up on the inte.net for these phrases I almost find nothing about them. now I have some questions:

1. What is the meaning of these phrases in the RS485 interface?
2. What does mean the word configuration as , configure as hardware or software? and are there changeable to each other after this configuration or not?

more information is available on this link :

Product information->Options->Optional interfaces

all datasheets of this PC are also available on this page.

any help would be appreciated.

Answer 1

The echo is can be a feature or a bug. As explained here , Some CPU use this as a form of "timing control" but it can create standing waves on the line which may create an undesirable behavior.

Termination and drop-point are essentially the opposite one from another. Either there is aa built-in termination or there is no termination and an option for you to add it. It is very much depends on your.network topology. You can read about it here and here .