Hello Dear Siemens Expert Community! 

I am working in a project, communicating a plc S7-1214C with two Schneider ATV630 drives through Modbus TCP/IP network. I can manage to read and write, a simple holding register without any problem. But, when I try to read or write multiple holding registers with one MB_Client function only, is impossible to acomplish it due that the S7-1200 plc does not support the modbus function 23 (I am not sure, if this is the number), anyway, does anybody know if there is some kind of a custom library to read/write multiple registers?

I made my own FB, written in SCL language, in order to do this. I could manage to read and write multiple registers, but only for one server, for the other one, it appears a status error (code 7002, and the help is not useful for this fault). And, although It communicates with one drive (internally appears a status error code 8200), but as I said, it works.

Let me show you the FB source code:

Hello,

sry, am I good understand that your block read and write to Slave with one request? Probably I don't understand your input parameters as there is definition OR, mean you can read or write, but not read AND write as one request. Of course (what is known to me) Siemens doesn't support FC 23. Don't know what is in TIA v14.

Hello!

The idea is to read OR write, not both at the same time, but with the function you can read or write multiple registers with only one request.

I know the MB_Client instruction has a LEN input to assign the amount of registers to be read or written, but as long as the plc does not support function 23, this feature is useless with this kind of drives (as I understand so far), so I had to find a different way to do it. One posibility would be, using one MB_Client instruction for every register I want to read/write (well, this is what I did with my code, but using a loop). But I don´t think this is "efficient coding".

Good news, the program is working fine (How? I don't know), maybe the power cycle was the answer

Anyway, if anybody knows a better way to accomplish what I did, it would be great!

Regards

Camilo Gorosito 

Hello,

ok, I was only think (you've mentioned FC 23) that you have solution as FC 23 is defined - read and write with one request.

MiloArg

Hello Dear Siemens Expert Community! 

I am working in a project, communicating a plc S7-1214C with two Schneider ATV630 drives through Modbus TCP/IP network. I can manage to read and write, a simple holding register without any problem. But, when I try to read or write multiple holding registers with one MB_Client function only, is impossible to acomplish it due that the S7-1200 plc does not support the modbus function 23 (I am not sure, if this is the number), anyway, does anybody know if there is some kind of a custom library to read/write multiple registers?

I made my own FB, written in SCL language, in order to do this. I could manage to read and write multiple registers, but only for one server, for the other one, it appears a status error (code 7002, and the help is not useful for this fault). And, although It communicates with one drive (internally appears a status error code 8200), but as I said, it works.

Let me show you the FB source code:

 

FUNCTION_BLOCK "MB_TCPIP_MRW"

TITLE = Modbus TCP/IP Multiple Read/Write registers

{ S7_Optimized_Access := 'FALSE' }

AUTHOR : Gorosito

VERSION : 0.1

//Function block for reading/writing multiple registers via modbus tcp/ip network, to Schneider ATV600 drives (registers from 40001 to 40033)

VAR_INPUT

  REQ : Bool;   // Execution request

  DISCONNECT : Bool;   // Desconnection with the server

  CONNECT_ID : UInt;   // Connection ID

  IP_OCTET1 : USInt;   // 1st IP octet

  IP_OCTET2 : USInt;   // 2nd IP octet

  IP_OCTET3 : USInt;   // 3rd IP octet

  IP_OCTET4 : USInt;   // 4th IP octet

  PORT : UInt;   // Port number

  RW : Bool;   // 0: reading 1: writing

  LEN : Int;   // Amount of data in order to read/write

END_VAR

VAR_OUTPUT

  DONE : Bool;   // Done (last datum was read/written correctly)

  Busy : Bool;   // Function busy

  Error : Bool;   // Fault from wichever of the telegrams

  Status : Word;   // Fault code

END_VAR

VAR_IN_OUT

  Storage_Addr : Array[1..32] of Int;   // 32 int array: reading/writing memory                                               // direction

END_VAR

VAR

  MB_CLIENT_MultiInstace {OriginalPartName := 'MB_CLIENT'; LibVersion := '2.1'} :       MB_CLIENT;   // MB_Client instansce (set as a multi-instance DB)

  MB_Mode : USInt;   // Function modbus type (0: reading, 1:writing)

  i : Int;   // Iteration variable

  j : Int;   // Iteration variable

  k : Int;   // Iteration variable

  IteracionUDint : UDInt;   // Iteration variable i in UDint format

  ReqAux : Bool;   // Auxiliar mark for MB_Client REQ input

  bBusy : Array[1..32] of Bool;   // 32 bool array to storage every Busy bit of every MB_Client function call

  DN : Array[1..32] of Bool;   // 32 bool array to storage every DN bit of every     MB_Client function call

  ErrorBufferBit : Array[1..32] of Bool;   // 32 bool array to storage every Error   bit of every MB_Client function call

  ErrorBufferStatus : Array[1..32] of Word;   // 32 word array to storage every   ErrorStatus word of every MB_Client function call

END_VAR

VAR_TEMP

  Data_Address : UDInt;   // Datum to read/write

  ErrorAux : Bool;   // Function fault

  ConnectIdAux : UInt;   // Auxiliar variable for connection ID

END_VAR

VAR CONSTANT

  LIMITE_CANT_DATOS : Int := 32;   // Constant that represent the maximum data amount that the function could read/write

END_VAR

BEGIN

//Depending on either the function is for reading or writing, it'll determine the MB_MODE value based on the INPUT parameter "RW"

IF #RW THEN

  #MB_Mode := 2;

ELSE

  #MB_Mode := 0;

END_IF;

//Test if the LEN value (amount of data to be read/write) is between the limits from 1 to LIMITE_CANT_DATOS

IF (#LEN > 0) AND (#LEN <= #LIMITE_CANT_DATOS) THEN

  //Loop cycle for requesting network data several times

  FOR #i := 1 TO #LEN DO

    //Converts iteration variable format

    #IteracionUDint := INT_TO_UDINT(IN := #i);

    //Increases holding register starting from the 40001

    #Data_Address := 40000 + #IteracionUDint;

    //Every MB_Client request depends on if the former MB_Client function has finished with a DN bit on or an error.

   //Except for the first one, that only depends if the MB_Client function is busy or not

      IF #REQ AND NOT (#bBusy[#i]) THEN

        IF #i = 1 THEN

          #ReqAux := TRUE;

        ELSE

          #ReqAux := (#DN[#i - 1] OR #ErrorBufferBit[#i - 1]);

          #DN[#i - 1] := 0;

        END_IF;

      ELSE

        #ReqAux := FALSE;

      END_IF;

      //MB_Client function call

      #MB_CLIENT_MultiInstace(REQ := #ReqAux,

                              DISCONNECT := #DISCONNECT,

                              CONNECT_ID := 1,

                              IP_OCTET_1 := #IP_OCTET1,

                              IP_OCTET_2 := #IP_OCTET2,

                              IP_OCTET_3 := #IP_OCTET3,

                              IP_OCTET_4 := #IP_OCTET4,

                              IP_PORT := #PORT,

                              MB_MODE := #MB_Mode,

                              MB_DATA_ADDR := #Data_Address,

                              MB_DATA_LEN := 1,

                              DONE => #DN[#i],

                              BUSY => #bBusy[#i],

                              ERROR => #ErrorBufferBit[#i],

                              STATUS => #ErrorBufferStatus[#i],

                              MB_DATA_PTR := #Storage_Addr[#i]);

  END_FOR;

//Set the error bit if some of the LEN MB_Client functions has set an error.

#j := 1;

#ErrorAux := FALSE;

  WHILE (#j<= #LEN) AND ((#ErrorAux <> 0)) DO

    #ErrorAux := #ErrorBufferBit[#j];

    #j := #j + 1;

  END_WHILE;

//If the last MB_Client call has finished correctly, it sets the DONE flag

  IF #DN[#LEN] AND NOT (#ErrorAux) THEN

    #DONE := TRUE;

    #DN[#LEN] := 0;

  ELSE

    #DONE := FALSE;

  END_IF;

//If there isn't any fault, then the FB proceeds to erase the error buffer

  IF NOT (#ErrorAux) THEN

    FOR #k := 1 TO 32 BY 1 DO

      #ErrorBufferStatus[#k] := 0;

    END_FOR;

  END_IF;

ELSE

  #Status := 0600;        //Error 0600, LEN parameter out of bounds

END_IF;

#Error := #ErrorAux;

END_FUNCTION_BLOCK

 As I always say, I am sorry for my english.

Any kind of help will be gratefully accepted, thanks!!

Regards

Camilo Gorosito

 

 

 Dear friend,

Ihave an incoming project with S7 1215 with ATV 660 , and i need to control the speed of the VFD through PID block.

can you please briefly explain how to read/write values/parameters from/to  VFD via Modbus TCP/IP?

I have a project with 1215c cpu and ATV 660 VFD

In need to control the speed of motors by controlling the frequency of vfd via PID control .

at the same time i need to take VFD data's through modbus TCP/IP communication.

 Kindly share the details how to do this config. bcz  I am new in these product

>But, when I try to read or write multiple holding registers with one MB_Client function only, is impossible to acomplish it due that the S7-1200 plc does not support the modbus function 23.

It is very difficult to find a Modbus Client or server that uses/implements/understands Function code 23. 

However, the standard Modbus Function codes are widely implemented.   The use of the standard Modbus code generally does not require writing code, it requires using the appropriate function code in the Modbus message along with addressing, byte count and data transfer information is required.

The standard Modbus Function Codes are listed below.  All those Function Codes are defined by the Modbus spec.  Not all clients/masters or server/slaves implement all of the standard function codes, but the device documentation lists which are supported.

Read Functions
Function Code 01  Read coil(s), single or multiple
Function Code 01  Read Discrete Input(s), single or multiple
Function Code 03  Read Holding Register(s) 4xxxx, single or multiple (integer - floating point format data)
Function Code 04  Read Input Register(s) 3xxxx, single or multiple (read only registers)

Write Functions
Function Code 05  Write single coil (mandated specific data format 0xFF00 or 0x0000)
Function Code 06  Write single Holding register 4xxxx

Function Code 15 (0x0F), Write multiple coils
Function Code 16 (0x10), Write multiple Holding Registers 4xxxx