I need read 30000 register type from modbus slave. The configuration is: CPU Quantum, from Ethernet 140NOE77101 to TSX ETG 100 ethernet-modbus, slave modbus.

I can read 40000 register type with Quantum I/O scanning, but I can't read 30000 register type.

Can you help me?

Thank you very much.

 

You are correct. Unfortunately, the company that originated Modbus protocol did not elect to provide for any commands other than read/write 4xxxxx registers. Why? The only reason that I can think of is efficiency. The most data can be moved in words. This is the same issue with the MSTR function. With Unity, the READ/WRITE VAR function does provide some more flexibility.

Have you considered configuring the Quantum serial port as master and connecting via serial direct?

 

Thank you for your interest.

I have questioned, but this configuration has two CPU's for redundant comunication proposit. Do you know if it is possible to do it?

Thank you very much.

 

Not sure what you mean by "the company that originated Modbus protocol" but, Modbus by Modicon supports Function Code 4 and Function Code 6 to read and write "Input Registers" (3xxxx) in addition to Function Code 3 and Function Code 16 for Read and Write "Holding Registers" (4xxxx).

 

I was mistaken about Function Code 6 because it writes single Holding Registers (4xxxx). Function code 4 reads 3xxxx "Input Registers" which are typically Analog Inputs derived from A/Ds which cannot be anything but read functions.

 

Going back to the original post, I think that the problem is that the scanning feature within the Quantum Ethernet module does not allow direct access to 30000 registers in the target. No problem - simply use BLKM in the slave to copy 30000 registers of interest to 40000 in the target.

This is a good idea anyway as it decouples the input registers and their arrangement from the master - so that the master does not have to be reprogrammed if there are changes in I/O allocation in the slave. It also allows flexibility in how the AI addresses are grouped functionally - eg, if three different modules are used for redundancy, the results can still be grouped in the 40000 area for reading from the master.

Cheers,
Bruce.

 

I too was confused by the original question. The issue is not with Modbus function codes but with the ability of a Quantum processor to read 3xxxx references from a slave device via the ethernet to modbus serial converter (ETG100). It is NOT possible in the Quantum controller to program a function to read anything but registers (4xxxx references) via Modbus Plus or Modbus TCPIP. Simple as that, the FBs in Concept and Unity only read registers. Nothing else. No need to debate which function codes work. This has nothing to do with Quantum redundancy, which, by the way works fantastically.

 

You have three solutions:

1. copy all 3x objects to 4x in the slaves

2. use CEV 174CEV30020(this gateway has internal option for converting 3x to 4x See the user guide 890USE19500) instead of ETG100

3. use the RS485 Modbus Port of Quantum. You have to program OUT_IN_MBUS or XXMIT function

 

Hi there,
One way to solve it, could be to use a gateway from HMS, see:
http://www.hms.se/support/support.asp?PID=110&ProductType=AnybusCommunicator

If you need more information, send me an email at:
[email protected]

//Pat

 

I've asked to schneider spain and told me that CEV 174CEV30020 is out of catalogue. From schneider the solution is to install an M340 like a gateway between ethernet and Modbus.

In this way I can read 3XXXX registers and the redundance is OK.

Are you agree with this solution?

Thank you very much.

 

For sure M340 is a solution but is not cost effective!! You could use Premium HSBY instead of Quantum HSBY but I can't suggest to you to change all your configuration!!

What about solution number 3 ??

How many modbus slaves you have?

You won't have any real advantages by using ethernet and a gateway if you have to read only few slaves. That's why I suggest to use the modbus port (no problem for redundancy the addresses of the modbus "masters" are managed by the two controllers)

 

I've to read seven slaves.

I've considered your solution 3 and I think is good.

Now I'm analysing the corrects parameters to configuring the instruction and then test it in the installation.

Very thanks.

 

I've been able to configure the primary and stand-by modbus quantum ports. Primary is adress 1 and stand-by is adress 129.

But I've not able to read registers from slaves.

I need to read 4XXXX registers from four slaves and 3XXXX registers from three slaves.

I'm using a XXMIT instruction and returns
107 and 120 failure code from status signal.

Could you help me?

Thank you very much.

 

107 Transmit message time-out (This error is generated when the UART cannot complete a transmission in 10 seconds or less. This error bypasses the retry counter and will activate the error output on the first error).

120 XXMIT could not set PLC UART

The XXMIT have not correct configuration!

See example
http://forums.mrplc.com/index.php?autocom=downloads&showfile=271