PLC supporting special Modbus commands

[glnassaf]

Hi,
I have a project in which I need to communicate with FMC Sybertrol flow computer in modbus RTU.
The flow computer has a whole range of registers that can be accessed using Modbus non standard function codes 67,68
(see http://info.smithmeter.com/literature/docs/mn09048l.pdf - page 3)

Is anyone familiar with a PLC that is able to send and receive special modbus commands?

Regards,
Assaf

 

[glnassaf]

Any ideas? No one here used non standard modbus commands?

Thanks,
Assaf

 

[Bullzi]

Assaf,
I have worked for a FMC Smith Meter Distributor for the last 23 years but have never worked on a SyberTrol. Omni, and Total Flow Flow Computers dominate the market here in the US. The Non-Standard Modbus is one of the reasons I suspect that the SyberTrol never took off.

Maybe this will help: I worked with a customer not long ago that was using a AB Compact Logix PLC with a Prosoft MVI56E-MNET Modbus TCP/IP Card. He connected it to several FMC Accuload III units and automated the whole station.

So you might look into the Prosoft line of Modbus Cards and see if they make one that you can add your own function codes or have those codes in them.

If I can help let me know.

 

[danw]

1) Special modbus commands are invented for specialty software.

You need to contact the vendor and find out what software the special Modbus commands were developed for.

2) Are the special commands doing something so critical that the standard commands can not be used for?

What would you be missing if you just used standard Modbus functions?

 

[JHarbin]

1) Special modbus commands are invented for specialty software.

You need to contact the vendor and find out what software the special Modbus commands were developed for.

2) Are the special commands doing something so critical that the standard commands can not be used for?

What would you be missing if you just used standard Modbus functions?

A quick glance at the manual indicates to me that most everything most people would want is available through standard Modbus functions.

 

[glnassaf]

JHarbin, thanks for enlightenment.
I checked again for all of the parameters the customer requires.
It appears they exist both on the special function address range and on the standard address range.
I will simply tell the customer we will read these parameters from the standard range and solve the problem quite easily!

Thank you all for helping!

Assaf