PmModbusMr - Driver for communication by the Modbus Master protocol

Before using this driver in the PROMOTIC application it is highly recommended to read the chapter: Communication using the PROMOTIC drivers.

Basic properties of the driver:

- Usage of this driver requires purchase of the PmModbusMr license. With the freeware version PmFree, or when developing the application (with development environment for tersting purposes), this component is always functional.

- The communication is done for Ethernet-client or for serial link (COM1, COM2 ...).

- The PROMOTIC application is the MASTER (i.e. it initiates the data transfer) from this communication point of view. For SLAVE communication can be used: PmModbusSl - Driver for communication by the Modbus Slave protocol.

- The driver is incorporated into the PROMOTIC system by means of the PmaComm object.

The driver supports the usage of both PmaCommMsg and PmaCommGroup objects. For common data transfers, it is easier to use the PmaCommGroup object.

For easy integration of this driver into the application it is handy to use: Preconfigurations in group "Modbus communication protocol"

- This is a network communication, i.e. one PmaComm object can communicate with multiple devices (the protocol supports multiple device addressing).

- The driver supports the TCP, RTU and ASCII transfer modes.

- It is possible to transfer standard 1-bit (bits) and 16-bits (registers) values and less standard 32-bits values of the float and long type and 64-bit values (float double precision).

- The driver can be used also for the JBUS protocol. The JBUS protocol is the subset of the Modbus RTU protocol. All implemented messages in this driver (see below) are also supported by the JBUS protocol.

Following Modbus data types are supported:

- b = Bit (1Bit):

In the PLC: 1bit. In the PROMOTIC application: data type Boolean.

- W = Word (2Byte Unsigned Integer):

In the PLC: 16 bits (value from 0 to 65535). In the PROMOTIC application: data type Long.

- I = Int (2Byte Signed Integer):

In the PLC: 16 bits (value from -32767 to +32767). In the PROMOTIC application: data type Integer.

- L1 = Long type 1 (4Byte Signed Integer):

In the PLC: 32 bits. In the PROMOTIC application: data type Long.

Only for messages of the 03, 04, 16 type.

The binary format of this type is the same as in PC, only the bytes order is changed (bytes order PC:1234, PLC:2143).

Use for example: Modicon, Wago, etc.

- L2 = Long type 2 (4Byte Signed Integer):

Identical as the previous data type, only the bytes sequence is different (bytes order PC:1234, PLC:4321).

Use for example: JUMO.

- L3 = Long type 3 (4Byte Signed Integer):

Identical as the previous data type, only the bytes order stays the same - as in the PC (bytes order PC:1234, PLC:1234).

- UL1 = ULong type 1 (4Byte Unsigned Integer):

In the PLC: 32 bits. In the PROMOTIC application: data type Double.

Only for messages of the 03, 04, 16 type.

The binary format of this type is the same as in PC, only the bytes order is changed (bytes order PC:1234, PLC:2143).

- UL2 = ULong type 2 (4Byte Unsigned Integer):

Identical as the previous data type, only the bytes sequence is different (bytes order PC:1234, PLC:4321).

- UL3 = ULong type 3 (4Byte Unsigned Integer):

Identical as the previous data type, only the bytes order stays the same - as in the PC (bytes order PC:1234, PLC:1234).

- LL2 = LongLong type 2 (8Byte Signed Integer):

In the PLC: 64 bits. In the PROMOTIC application: data type Double. (bytes order PLC:87654321)

Only for messages of the 03, 04, 16 type.

8-byte integer cannot be stored in requested data type with full accuracy. Here it is stored to value of the Double type, but for some very big numbers the accuracy may suffer (maximum difference +-2047).

Use for example: Energy meter iEM3100(Schneider-Electric), Multimeter EPM-07S(ENTES) ...

- R = Float type 1 (4Byte - IEEE 754):

In the PLC: 32 bits. In the PROMOTIC application: data type Single.

Only for messages of the 03, 04, 16 type.

The binary format of this type is standardized by IEEE-754, so it is the same as in PC, only the bytes order is changed (bytes order PC:1234, PLC:2143).

- R2 = Float type 2 (4Byte - IEEE 754):

Identical as the previous data type, only the bytes sequence is different (bytes order PC:1234, PLC:4321).

Use for example: ABB AC500.

- R3 = Float type 3 (4Byte - IEEE 754):

Identical as the previous data type, only the bytes order stays the same - as in the PC (bytes order PC:1234, PLC:1234).

- D1 = Float Double-precision type 1 (8Byte - IEEE 754):

In the PLC: 64 bits In the PROMOTIC application: data type Double.

Only for messages of the 03, 04, 16 type.

The binary format of this type is standardized by IEEE-754, so it is the same as in PC, only the bytes order is changed (bytes order PC:12345678, PLC:21436587).

- D2 = Float Double-precision type 2 (8Byte - IEEE 754):

Identical as the previous data type, only the bytes sequence is different (bytes order PC:12345678, PLC:87654321).

- D3 = Float Double-precision type 3 (8Byte - IEEE 754):

Identical as the previous data type, only the bytes order stays the same - as in the PC (bytes order PC:12345678, PLC:12345678).

Recommended parameters values:

Number of data bits	8 for RTU mode, 7 for ASCII mode
Number of stop bits	1 if parity is used, 2 if parity is NO

Recommended values for the Ethernet-client parameters:

TCP/UDP port number	502 (for MODBUS TCP/IP data type)
Ethernet transfer type	TCP (for MODBUS TCP/IP data type)

Description and recommended values for the Protocol parameters:

Protocol data type	Only for Ethernet. Specifies the protocol data form. It is possible to set: MODBUS TCP/IP - Standard Ethernet MODBUS communication. Compared to the data for serial link a special header is included and it is transferred via Ethernet TCP on port 502. The same data as for serial link - This option can be selected, for example, if the device is equipped with the serial link and it is connected to the Ethernet through the RS232/Ethernet converter. If the converter does no modifications to the transmitted data, then it is a very easy way how to communicate via Ethernet with devices not equipped with Ethernet interface.
Response receipt timeout	Only for serial link. The recommended value is for example 2000 ms. The time (in milliseconds) the driver is waiting for the response on sending the message. If no response comes during this time, then the transfer of the message is terminated (the onEndOfTransfer event is triggered with error 24 or 66).
Transfer mode	The MODBUS protocol includes two transfer options. In the parameters of the PmaCommMsg object message, the mode can be changed (for special cases, when necessaray to communicate with multiple PLCs in different modes). RTU - Most commonly used transfer mode, where the data is being transferred in binary form. ASCII - The transfer mode, where the data is transferred in ASCII form. This mode is not supported for MODBUS TCP/IP.

The communication description by the PmaCommGroup objects

The PmaCommGroup objects can be used for this driver. For usual data transmissions it is more favourable than using the PmaCommMsg object.

The variables in the PmaCommGroup object (or even better the variables in the PmaData object with ExtComm data extension) can be of arbitrary number, type and order. The driver uses optimalised internal communication messages for reading the data from the device.

All variables are read (if the "Data refresh enabled" configurator is checked). When writing to the variable, only the single value is sent (if the "Auto send when writing to item" configurator is checked).

Description of the "ItemID" configurator:

ItemId is the text identifier of the item that is used for addressing the value in the device. The ItemID configurator tells the driver how to receive or send the item value. The text can be written manually, or it can be assembled in the window opened by the button to the right of the configurator. Macro expression can be used for input (it is evaluated after starting the application).

The text can be for example "dev2.Ri33.W" representing:

dev2 = the item is in the PLC (device) with an address of 2. The devD (=default address) can be entered instead of the number and the PLC address will be determined according to the "Default PLC address" configurator.

Ri33 = is from the data area "Input registers on relative address 33. The address 33 is only relative address. During communication, the value defined in the "Area base addresses" configurator is added to this number.

A list of data areas:

- Bo = the area "Coil status / Output bits".

For data receive the Modbus function is used: FN01 (Read Coil Status, Read Output Bits).

For data write the Modbus function is used: FN05 (Force Single Coil, Write 1 Bit).

- BoM = the area "Coil status / Output bits".

For data receive the Modbus function is used: FN01 (Read Coil Status, Read Output Bits).

For data write the Modbus function is used: FN15 (Force Multiple Coils, Write n Bits).

The difference from the Bo area is only the write method (FN15 is used instead of FN05).

- Bi = the area "Input status / Input bits".

For data receive the Modbus function is used: FN02 (Read Input Status, Read Input Bits).

Data write is not possible..

- Ro = the area "Holding/Output registers".

For data receive the Modbus function is used: FN03 (Read Holding/Output Registers).

For data write the Modbus function is used: FN16 (Preset Multiple Registers, Write n Registers).

- RoS = the area "Holding/Output registers".

For data receive the Modbus function is used: FN03 (Read Holding/Output Registers).

For data write the Modbus function is used: FN06 (Preset Single Register, Write 1 Register).

The difference from the Ro area is only the write method (FN06 is used instead of FN16).

Caution: The function FN06 cannot write 4 and more byte values (for example data types Long and Float).

- RoB = the area "Holding/Output registers". For transfer of individual bits.

For data receive the Modbus function is used: FN03 (Read Holding/Output Registers).

For data write the Modbus function is used: FN22 (22-Mask Write Register).

Example: RoB38.0 is read/write of 0.bit in register 38.

- Ri = the area "Input registers.

For data receive the Modbus function is used: FN04 (Read Input Registers).

For data write the Modbus function is used: FN16 (Preset Multiple Registers, Write n Registers).

- RiS = the area "Input registers.

For data receive the Modbus function is used: FN04 (Read Input Registers).

For data write the Modbus function is used: FN06 (Preset Single Register, Write 1 Register).

The difference from the Ri area is only the write method (FN06 is used instead of FN16).

Caution: The function FN06 cannot write 4 and more byte values (for example data types Long and Float).

W = in PLC has the data type Word

Description of the "PmaCommGroup > Parameters > Special Parameters" configurator:

Default PLC address	The address defined here can be used for definitions in the "ItemID" configurator for the variables in this object (i.e. the variables on the "Data" page or in the ExtComm data extensions). The address can be entered in ItemID: - as for example dev1... - then the value will be read from the PLC device with address 1. - or devD... - the "D" character means default, (it means that the address is taken from this configurator). This parameter can be modified and read in the script during runtime by methods: SetSpecParam("SlaveAddr") and GetSpecParam("SlaveAddr").
Area base addresses	Here, the addresses of the beginnings of the data areas are entered (Bo, Bi, Ro, Ri). The addresses for these areas are preset to 0. (if the preconfiguration for a specific device is not used - see Preconfigurations / Communication / Modbus communication protocol). For another PLC types the addresses my be different (e.g. the addresses do not begin with 0, but with 1 or 40001, etc.). While communicating, the "Data item address" is modified as a sum of the relative item address (defined in the ItemID identificator) and the area base address.
Max.number of variables received in one message	For each area (Bo,Bi,Ro,Ri) the maximum number of variables to be transmitted in one communication message is defined here. These values depend on the device type to communicate with (some devices support transmissions of low register numbers in a single message, other support higher numbers) - this specification can be found in the device documentation or must be tried/tested. The preset values are 64 for Bo and Bi, 32 for Ro and Ri (if the preconfiguration for a specific device is not used - see Preconfigurations / Communication / Modbus communication protocol). The preconfigured values are very low. Increasing these values (if the device allows it) may cause higher communication speeds because the transmitted data can be sent in a lower number of communication messages.

Default PLC address

The address defined here can be used for definitions in the "ItemID" configurator for the variables in this object (i.e. the variables on the "Data" page or in the ExtComm data extensions). The address can be entered in ItemID:

- as for example dev1... - then the value will be read from the PLC device with address 1.

- or devD... - the "D" character means default, (it means that the address is taken from this configurator).

This parameter can be modified and read in the script during runtime by methods: SetSpecParam("SlaveAddr") and GetSpecParam("SlaveAddr").

Area base addresses

Here, the addresses of the beginnings of the data areas are entered (Bo, Bi, Ro, Ri).

The addresses for these areas are preset to 0. (if the preconfiguration for a specific device is not used - see Preconfigurations / Communication / Modbus communication protocol). For another PLC types the addresses my be different (e.g. the addresses do not begin with 0, but with 1 or 40001, etc.).

While communicating, the "Data item address" is modified as a sum of the relative item address (defined in the ItemID identificator) and the area base address.

Max.number of variables received in one message

For each area (Bo,Bi,Ro,Ri) the maximum number of variables to be transmitted in one communication message is defined here. These values depend on the device type to communicate with (some devices support transmissions of low register numbers in a single message, other support higher numbers) - this specification can be found in the device documentation or must be tried/tested.

The preset values are 64 for Bo and Bi, 32 for Ro and Ri (if the preconfiguration for a specific device is not used - see Preconfigurations / Communication / Modbus communication protocol).

The preconfigured values are very low. Increasing these values (if the device allows it) may cause higher communication speeds because the transmitted data can be sent in a lower number of communication messages.

The communication description by the PmaCommMsg objects

The PmaCommMsg object can be used for special communications, that cannot be executed by the PmaCommGroup object. For example by the "XX-User defined opened function" type message it is possible to compose any Modbus message types, that are not directly supported by the driver.

The address of the SLAVE station from which it is read or to which it is written, must be entered in each message. This address is entered on the "Data-sent" page of the message in the "Slave" variable (e.g. for the Modicon, valid slave addresses are in the range of 0-247).

The address 0 is used for the broadcast, i.e. for the messages received by all stations (if the Modbus protocol is used on higher network level, then the broadcast may not be allowed). The driver sends these messages but does not wait for response - therefore it is not relevant to set address 0 for messages that are to read (e.g. messages 01 to 04).

Further the address of the variable in the station is entered in the Data-sent in the "Addr" variable. The address value is supposed to be from 0 by default. But some devices (e.g. Modicon, GE-Fanuc) are addressed from 1 and that's why it is necessary to enter the Addr value decreased by 1 at these stations.

The maximum number of values (states, registers) in one message differs according to the PLC device. It can be for example 32, 125, 128, 1024, etc.

List and description of the communication messages:

01-Read Coil Status (Read Output Bits): This message reads n output states (1-bit values) from the specified address Addr.

02-Read Input Status (Read Input Bits): This message reads n input states (1-bit values) from the specified address Addr.

03-Read Holding Registers (Read Output Registers): This message reads n output registers (16-bits values) from the specified address Addr.

04-Read Input Registers: This message reads n input registers (16-bits values) from the specified address Addr.

05-Force Single Coil (Write 1 Bit): This message writes into one state (1-bit value) to the specified address Addr.

06-Preset Single Register (Write 1 Register): This message writes into one register (16-bits value) to the specified address Addr.

15-Force Multiple Coils (Write n Bits): This message writes into n state (1-bit values) from the specified address Addr.

16-Preset Multiple Registers (Write n Registers): This message writes into n registers (16-bits values) from the specified address Addr.

22-Mask Write Register (Modify Register Using both AND & OR Masks): This message writes defined individual bits into a single register (16-bit value) by using the AND and OR mask.

There are following variables on the "Data-sent" page:

Slave - Address of the slave device, i.e. PLC address.

Addr - the address of the register where the bits will be written.

AND_Mask - mask of bits to be zeroed

OR_Mask - mask of bits to be set

There is no varible on the "Data-received" page.

XX-User defined opened function:

User-defined Modbus message. It can be used for message types that are not otherwise supported by this driver. The designer can define the complete content of the message (received or sent), but the order and data type of the DataX variables must be observed carefully.

The variables DataX (in Data-sent and in Data-received) represent data in Modbus protocol from the character Function (without this character) and up to the character CRC (for serial RTU, without his character) or up to the end of the message (for Modbus TCP/IP). For ASCII transfer mode the data is defined the same way as for RTU mode and the driver then transforms such data into ASCII form.

There are following variables on the "Data-sent" page:

TXLength - The size of transmitted data (in bytes). This is not the total size of the sent mesage, but just the portion that is stored in the DataX variables on this page. The value -1 means that all DataX variables on this page are to be sent.

RXLength - Maximum expected size of accepted data (in bytes). This is not the total size of the received mesage, but just the portion that will be stored in the DataX variables on the "Data-received" page. The value -1 means that the expected size will be calculated as the total lenght of all DataX variables on the "Data-received" page.

- if the size is defined less than the currently received data, then an error occurs and the received data is not processed.

- if the size is defined greater than the currently received data, then the transfer takes longer (the system will wait for timeout), but the received data is processed.

Slave - Address of the slave device, i.e. PLC address.

Function - Number (code) of Modbus function. For example 1 = Read Coil Status, 17 = Report Slave ID etc.

DataX - User-defined data that are to follow after the function number (without the control sum). There may be multiple variables (of different data types) on the page, but only those that fit into the message will be sent (i.e. according to the value in TxLength).

There are following variables on the "Data-received" page:

Length - The ammount of received data (in bytes). It is not the total size of the received message, but only the portion that is stored in DataX variables on this page.

Function - The number (code) of Modbus function. Normally, there should be the same value here as on the "Data-sent" page.

DataX - Received data. There may be multiple variables (also different data types) on this page, but only those that were in the received message will be filled.

History:

Pm9.00.07: Generalization: Added Modbus data type: UL1 = ULong type 1 (4Byte Unsigned Integer), UL2 = ULong type 2 (4Byte Unsigned Integer) and UL3 = ULong type 3 (4Byte Unsigned Integer)

Pm8.03.25: Fixed bug: Optimized PmaCommGroup variables assignment into individual communication messages.

Pm8.03.24:

- Generalization: Added Modbus data type: LL2 = LongLong type 2 (8Byte Signed Integer)

- Fixed bug: On data receive it was not teste whether the answer came from the correct device.

Pm8.03.19: Generalization for send broadcast type messages by PmaCommMsg object, i.e. if the defined slave address is 0, then the broadcasted message will be received all stations in the network.

Pm8.03.10: Generalization for data writing by Modbus function FN06 (area RoS and RiS).

Pm8.03.01: Fixed bug: Reading and writing bit in the registry (i.e. reading and writing area RoB) did not work correctly.

Pm8.02.11: in the message of the XX-User defined opened function type the number of bytes of received data was not saved into the "Data-received" variable. The total message lenght was saved instead.

Pm8.02.03: Fixed bug: Fixed transmission of messages of the XX-User defined opened function type.

Pm8.02.00:

- Now it is possible to transmit messages for user-defined functions. In the PmaCommMsg object parameters, it is now possible to set the function: XX-User defined opened function.

- Now it is possible to write individual bits (in the PmaCommGroup and PmaCommMsg objects) by the 22-Mask Write Register (Modify Register Using both AND & OR Masks) Modbus function.

Pm8.00.05:

- into the PmaCommGroup object, there has been added a New configurator Default PLC address. In some cases the new configurator allows easier address input and administration.

- Fixed bug: there was sometimes an error when sending values in the PmaCommGroup object.

Pm8.00.03:

- Generalization: Added Modbus data type: R2 = Float type 2 (4Byte - IEEE 754)

- Fixed bug: the PmaCommGroup object sometimes incorrectly received the bit values.

Pm8.00.02: Fixed bug: the PmaCommGroup object was unable to read/write 4-byte values (Long, Single).

Pm7.02.03: Fixed bug: data sending error in ASCII mode.

Pm7.02.02: Generalization: Added Modbus data type: L1 = Long type 1 (4Byte Signed Integer) and R = Float type 1 (4Byte - IEEE 754)

Pm7.01.00: Implementation of the Ethernet communication

PROMOTIC 9.0.8 SCADA system documentation - MICROSYS, spol. s r.o.

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