Modbus - ZPROS??

[mariobo11]

Hy!

Is there any serial communication protocol called MODBUS-ZPROS?

I'm working on some project and i have to pick PLC who support that kind of protocol. I have never heard for that protocol but i would like to ask u all if someone knows something.

Thank you!

:site:

 

[danw]

I have no knowledge of Modbus -ZPROS, but I suspect that Modbus-whatever is a combination of publicly documented function codes (from Modbus.org) AND some private, proprietary function codes, designed for a manufacturer's specific tasks. Hopefully the private function codes occupy those function code values allocated for private codes.

I have this note regarding categories of Modbus Function Codes, from an unknown source:

There are 2 categories of MODBUS Function Codes, ie
1. Public Function Codes
2. User-Defined Function Codes (otherwise known as private function codes)

The set of Public Function Codes comprises 2 sets of function codes:
1. Assigned Function Codes
2. Unassigned Function Codes, set aside for future assignment.

Public Function Codes
- are well defined function codes ,
- guaranteed to be unique,
- validated by the modbus.org community,
- publicly documented at modbus.org,
- have available conformance tests,
- include both assigned function codes as well as unassigned function codes reserved for future use.

User-Defined Function Codes
- There are two defined ranges of user-defined function codes, ie
- 65 to 72 decimal (0x41 to 0x58), and
- 100 to 110 decimal (0x64 to 0x6E).
- The user can select and implement a function code without any approval from modbus.org.
- There is no guarantee that the use of the selected function code will be unique.

 

[mariobo11]

That is true. I found out that it is private protocol who are using only one company in Croatia.

Thanks anyway
:site:

 

[danw]

If you just need Modbus RTU, then additional private function codes might not be a serious drawback.

Modicon Modicon uses a proprietary function code (7Eh) to do PLC configuration with their own software. They don't publicly document the 7E function code, but it's their software, they dont' have to.

It's expected that the user uses the software which then (transparently) uses the 7E function code in the manner they've designed it for.

As long as the publicly documented function codes do what you need to do, then the it will work out just fine.

If you need Modbus-whatever, then you need Modbus-whatever.