Modbus Function Code 6
Modbus data structure: 8 data bits, 1 or 2 stop bits, and no parity bit. Here is the piece of code that I use to read a few VFD modbus holding registers. 6 Function Codes Modbus protocol defines several function codes for accessing Modbus registers. Read Function Codes For each Modbus table type, a specific Modbus Read Function Code value is used; this is a built-in part of the Modbus protocol. it's open and i think there have few version of modbus including tcpip. A request consists of a modbus register and a modbus function code (FC) Supported nodejs versions are 6, 8 and 10 as well as node-red in version 0. the Modbus protocol imbedded into each network's packet structure provides the common language by which the devices can exchange data. Note that the Read Function and Write Function cannot both be set to "Disabled". 3 Function code/Exception code MODBUS Function code used for FLXA402 Function Function Code (hex) Read Coils 01 Write Single Coil 05 Write Multiple Coils 0F Read Input. I know that word acces (modbus function 06) to this address area would work because when i tried communication with s7-200 where i could choose the function code manually it worked without problems, but this FB in TIA Portal (mb_master) lets me only to choose Read/Write/Diagnostic mode not the function code and automatically chooses the funciton code by the address, which kinda sucks in my. Function code = 0x03 (3). The listing below shows the modbus codes supported by Modicon: I use function code 03 and function code 16 for modbus testing and this function code that is most commonly used in general. uModbus implements both a Modbus client (both TCP and RTU) and a. Template is used by Fenix Server which work from one side like WebSerwer ans second side like Modbus or S7 client. Refer to Register Map on page 12 for details. "Modbus RTU Bit sequence. After the circuit connections are completed and the code is uploaded to Arduino Uno now its time to connect the USB to RS-485 Module to the PC where the Modbus Slave Software is installed. “This function code is used to write a single output to either ON or OFF in a remote device. For example, the expression 14 Mod 4 evaluates to 2. Failure to do so will prevent the device from accepting the upload. It could also indicate that. MVI56-MCM ♦ ControlLogix Platform Contents Modbus Communication Module User Manual ProSoft Technology, Inc. Customize built-in webpage for users Web to Serial. I am using NI Lookout to interface and collect data with the Modbus serial object. 11: The Slave Address (11 hex = address17 ) 06: The Function Code 6 (Preset Single Register). the 7800 SERIES parameters to ModBus™ registers. 1 01 (0x01) Read Coils This function code is used to read from 1 to 2000 contiguous status of coils in a remote device. The function code field of the message frame will contain two characters (in ASCII mode), or 8 binary bits (in RTU Mode) that tell the slave what kind of action to take. At the word level, Modbus function code 4 (read input register) or Modbus function code 3 (read holding register) can be used. The IR5500 has a two-channel Modbus (or single Modbus and single HART) compatible interface for communication with the control room equipment such as programmable logic controllers (PLCs). Specific Modbus Function Codes For reading data from the device or to carry out commands, the services listed in the table, also called »Function Codes«, are supported. If you are using INTERNAL COILS, use FC1, but then your modbus address 0h is a PHYSICAL INPUT (X1) and is read using Modbus Function Code 02, as indicated in the address picker. The objective of this document is to describe the function codes used within the framework of MODBUS transactions. It allows you to access and change data points in a connected slave device using either the RTU or ASCII Transmission mode. Configure modbus-in nodes for every possible address you want to supply, gather and prepare a response in the flow and conclude with a modbus-out node to transmit the respose back to the client. Modbus Function Code: 1, 5, 15 Modbus Start Address: 4001 Modbus Block Size: 500 Number of Blocks: 1 Primary use: Clear min/max registers on command. The code functions accepted by MODBUS are represented by a byte, which accept one of the values 1 to 255 (the codes between 128 to 255 are reserved for exceptions). hello this is John Renault they welcome to another Modbus video we do these from time to time and today… Continue Reading. Moondru Mudichu Polimer Tv Serials. master user Write data from slave device register. Design built-in webpages according to project requirements and realize webpage control, web page data acquisition and other functions. 1] for information about extending the slave to support additional Modbus. org community, publicly documented and guaranteed unique. 7 MODBUS Function Code: Select one of the following MODBUS function codes: 01 – Read Coil Status 02 – Read Input Status 03 – Read Holding Registers 04 – Read Input Registers. Page 5 of 193 February 11, 2011. Figure 6: Detailed Function Code Example 1. 2 If Controller Is Configured to Support Decimal Places, Then the Controller’s Storage Method for a Parameter Affects Values Read. Therefore, a complete definition of where to find a piece of data requires both the address (or register number) and. The function code field of a MODBUS data unit is coded in one byte. The Modbus Function 10 is used to Preset Multiple Registers (4x references) in a Modbus Slave device. CoolPlug physical connection to Modbus is Two-Wire EIA/TIA-485 standard interface via 485-A and 485-B terminals, recommended by Modbus specification. BACNET/IP Interface 45 6. Modbus are mostly used in PLCs (Programmable Logic Controllers). The function code field of a MODBUS data unit is coded in one byte. RFC 3xxx MODBUS Application Protocol May 2002 go to wait excep_run send mb_excep_rsp_pdu with an execution exception code go to wait For an exception response, the server returns a function code that is the original function code plus 0x80, ie with its most significant bit set to 1. So FC16, for instance, is function code 16 decimal or 0x10 hex: the Preset Multiple Registers command. Request data frame. Using MODBUS with Series C Controllers iv Omega. 6/1112-0815/E 5/18 3. However, no response will be returned. Introduction to Function Codes The Modbus® function codes implemented for the iMAG 4700/AG3000 consist of the following: Function code Description Hex Decimal 0x03 03 Read Holding Register 0x04 04 Read Input Register 0x06 06 Write Single Register 0x10 16 Write Multiple Registers For more details, see the appendix. Functions 1, 2, 3 and 4 write the data received from the slaves to the ‘Data Table Write Addresses’, and functions 5, 6, 15 and 16 send to slaves the data read from the ‘Data Table Read Addresses’. Table 1-1 Parameter Description REQ Enables communication. In CommReq data block, the Modbus TCP address is 1. Programming instructions 6. The function code used determines the Modbus table to be read. Modbus RTU Function Codes Supported: "03" Read Holding Registers "06" Preset (Write) Single Register Reading (03) and Writing (06) Parameters The Register address equals the Parameter number. 20 6 Function codes descriptions 6. When a slave is asked to perform a function code, it uses the parameters of the function to execute that well-defined behavior. MODBUS RTU Function Code Function 01 Read Output Table 02 Read Input Table 03 Read Holding Registers (when addressing mode is 584/984, this function is used to ac-cess analog output registers). I use this library… I have no made any modification to the code: Github user 4-20ma “Modbus Master” see the modbus master files inside src folder, notice I copy crc16. It is a widely accepted protocol due to its ease of use and reliability. R[0-125] signed int and Mb. Supported Functions. Overview The present guide describes the implementation of the Mobus Protocol on the Modbus communication interface. Bit(s) 0 1 = Stop, 0 = Not Stop 1 1 = Start, 0 = Not Start. This signature will alert if 3 exception responses are seen in a short period time. This defines the message type and the type of action required by the slave. The Modbus Encapsulated Interface (MEI) is exposed through a documented public function, without being further explained. The only dependence is the pySerial module (also pure Python). Modbus was always capable of 64k register addresses that requires what was called 6 digit addressing: (4)xxxxx. Function Code: 8 bit value which is the function code in the query OR'ed with Hex (80), indicating the slave either does not recognise the query or could not carry out the action requested. Provided no errors occurred, the slave (SE-330) will Modbus Function Code 5 (Force Single Coil) is. For the input terminal in the example below, Modbus function code 2 (read input status) can be used to read the input points at the bit level. The Preset data values written in to a Modbus register are 16-bit values. function code ini yang akan dibahas di artikel ini. The result of reading is stored in dest array as word values (16 bits). • Direction of data transmission (master → slave or slave → master). function codes. The Virtual I/O Module 2 (VIM2) with Modbus TCP/IP Master Driver supports the following Modbus communications protocol function codes to read and write values to and from a Modbus slave device, as specified by the Modbus Application Protocol Specification from Modbus-IDA. Modbus on CMMP-AS-- M3/M0 Seite 6 von 7 Application Note – Modbus on CMMP-AS- -M3/M0 – 1. FUNCTION CODE 1 byte Function code ($01 / $04 / $10) DATA BYTES n bytes Data as response or command 1. Serial interface modules Operating Instructions, 03/2009, A5E00124881-05 7 Preface 1 How the Manual is Structured This manual volume is supplementary to the ET 200S Distributed I/O System manual. 5 Read Discrete Inputs (Function Code 2) 43 6. The Modbus protocol establishes the format for the master’s query by placing into it the device (or broadcast) address, a function code defining the requested action, any data to be sent, and an error–checking field. Serial Data Transfer - RS485 Modbus – Protocol 6 1. Each bit is sent as a voltage. async — Twisted Async Modbus Client; constants — Modbus. Function Code (one byte denoting the function ID, in this case '16') Starting Address (two bytes representing the modbus register at which to begin writing) Register Quantity (two bytes denoting the amount of registers to write) Byte Count (one byte representing the quantity of bytes being written. PM00488 Revision 3. When communicating to multiple Modbus devices through a Gateway each with a unique unit ID, either include the unit ID in the Modbus specific address or set it in the address mapping for the device. CANopen General Reference 43 13 2B 6. In the fourth column, I/O Type, select Read Holding S16 (3) or select from any of the other Modbus register types depending on your hardware. I guess I should probably make a support case for this. common — Twisted Async Modbus Client; client. Arduino based PLC will work always as a TCP/IP server with this library. MODBUS TCP/IP For H2-EBC100 4-6 MODBUS TCP/IP Ethernet Base Controller Modules, 3rd Edition, 11/04 MODBUS 584/984 Addressing for Function Code 3 Clients This memory map offers duplicate registers from the 30001 range and Bit memory data type into the 411000 range for clients/masters that only support function code 3. Modbus Protocol -Technical description Page 3 2. The Modbus specification does not define how the data in these registers is to be interpreted, for example as signed or unsigned numbers, binary coded decimal (BCD) values, etc. The Modbus RTU Function 06 is used to Preset a Single Register (4x references) in a Modbus Slave device. But physical address in memory should not be confused with data reference. Functions/Function Blocks) Describes specifications of instructions an d functions that can be used in programs. The composition of data varies with function codes. In a standard MODBUS RTU network, there is one Master and up to 247 Slaves. FC An abbreviation of function code Master A name for the side that requests function execution MODBUS device A device used in communications via the MODBUS protocol Request message A message that requests function execution to slaves. 6 / 14 Siemens A6V10881143_en--_c Smart Infrastructure 2019-04-25 Push-button addressing Display current address (digits in reverse order) The Modbus address can be set without a separate tool by using the push-button and LED. Many code samples and real world sample programs. MODBUS RTU Master RTU Slave TCP Client Download Purchase Contact. uModbus implements both a Modbus client (both TCP and RTU) and a Modbus server (both TCP and RTU). The Modbus server we've configured supports Modbus function codes 3, 6, and 16 for direct read and write access to the hold registers--the data we've pointed to our Modbus slave block. Modbus is a simple Modbus TCP/RTU Client/Server with a simple API. Function Code 6 and Function Code 16 are used to write data to the MPS. About Modbus. The CRC is wrong. Read Function Codes For each Modbus table type, a specific Modbus Read Function Code value is used; this is a built-in part of the Modbus protocol. Valid function codes are from 1-255, but not all codes will apply to a module and some codes are reserved for future use. Modbus RTU is an open, serial (RS-232 or RS-485) protocol based on master/slave or client/server architecture. Then the command-in-Hex follow. Supported function code 3 read holding register 16 write multiple register Broadcast No Standard Modbus over serial line V1. 1Actually both straight and crossed cables are acceptable if the Modbus device features an auto-sense Ethernet port. transaction oriented Understanding the Modbus Protocol Page 6 Built with Apache Forrest. Using Campbell Scientific Dataloggers as Modbus Slave Devices in a SCADA Network 1. A large number of devices have the TCP/IP modbus protocol becoming one of the most commonly used protocols at industrial level, this time we created a routine for ESP8266 as a slave Mobdus TCP/IP, we created this routine based on this Example Update ESP8266 Industrial Modbus TCP IP V2. This address is passed to data frame as is. uModbus or (μModbus) is a pure Python implementation of the Modbus protocol as described in the MODBUS Application Protocol Specification V1. You can use this tool to vulnerability assessment a modbus protocol. The modbus_read_registers() function shall read the content of the nb holding registers to the address addr of the remote device. Information in this document is subject to change without notice. However, no response will be returned. Must use Server table in “ECOM100 Server Client Mapping. 5) Function Code (1 byte) 6) Data bytes (n bytes) The most important bytes for this frame are the Unit Identifier, the Function Code and the Data bytes. MODBUS function codes are elements of MODBUS request/reply PDUs. VAR_OUTPUT. Modbus MFU Option Card Installation Manual 2 of 64 Publication PUB091-004-00_0219 The Modbus card described in this manual has been designed to fully comply with Modbus. The function code used determines the Modbus table to be read. Fenix can share data from Modbus or S7 devices in WebBrowsers. If not sufficient this services can be extended using custom function code and application specific data models. MODBUS® TCP FOR THE MICROCHIP TCP/IP STACK DS00001568A-page 4 2013 Microchip Technology Inc. The function number is encoded in 7 bits. the address of the first coil specified, and the number of coils. This defines the message type and the type of action required by the slave. h header file includes more function code definitions, such as: • ReadCoil 1 • ReadDiscreteInputs 2 • WriteSingleRegister 6. Try setting Modbus/TCP Port preference to this destination or source port. ok so I have Experion server that is sending my c# program a code function 6. WriteSingleCoil // WriteSingleRegister is Modbus function code 6. Function code 4 - Read Input Registers (read-only integers) Each of these different data types are stored in a different area of memory, according to Modbus, so you can think of the different function codes as different offsets into the data registers of Modbus. Holding registers: Addressed as analogues (each new address maps to a 16-bit register), can be read from or written to and have a base address of 40001 in modbus speak, and are accessed using function codes 3, 6 & 16. 1 Option H2. Modbus Function Codes 2 and 4. org for more details. Refer to the section below for details. Thu Jan 6, 2011 by jmccrohan in , , , , , , is an industry standard communications protocol for electronic devices. OVERVIEW Modbus RTU is an open, serial (RS-232 or RS-485) protocol derived from the Master/Slave architecture. attached pic So, if you are not using any physical inputs, do not use FC 2 ---- use FC 1. The above code work fine with FUnction code 3. Features: Fully user compliant Modbus TCP Server; fully compliant Modbus RTU Slave; Supports up to 400 Modbus registers for both Modbus TCP and Modbus RTU; Supports Modbus Function Codes 1,2,3,4,5,6,7,15 and 16; All Modbus TCP Server devices map directly to a Modbus RTU network; Effortless browser based configuration; 10/100 BaseT operation; Includes Ethernet Device Management Tool; No. Companies, names and data used in examples herein are fictitious unless otherwise noted. , to set 0x0004 you might need to set [4,0]. In such case, the unit identifier tells the Slave Address of the device behind the gateway. This command is writing the contents of analog output holding register # 40002 to the slave device with address 17. 11: The Slave Address (11 hex = address17 ) 06: The Function Code 6 (Preset Single Register). What are the supported Modbus Function Codes for a M221 controller? Welcome to the Schneider Electric corporate Website. 0 and others. 2 Modbus RTU connection to the SIMOCODE pro device Connecting Modbus RTU to the SIMOCODE pro V Modbus basic unit Modbus RTU can be connected to the SIMOCODE pro V basic unit both viathe connecting. Function Code terbagi menjadi 3 kategori. ReadHoldingRegisters // ReadInputRegisters is Modbus function code 4. However, no response will be returned. R[0-125] signed int and Mb. Array might need reverse ordering. Holding registers: Addressed as analogues (each new address maps to a 16-bit register), can be read from or written to and have a base address of 40001 in modbus speak, and are accessed using function codes 3, 6 & 16. For example, a decimal "1" is used for Parameter 1, a decimal "39" is used for Parameter 39, etc. The interface can be connected to a RS485 Modbus network and can be controlled by a Mobus master station over this network. address: number (-) Start address of the first holding register or coil in the write. Modbus tcp api. We listed the supported function codes on the Connecting to Modbus Device page. command and response format as the functions listed in the Modicon Modbus Protocol Reference Guide (January 1985), form PI-MBUS-300 Rev B. Page 8 / 21 Polling Data Registers from Modbus Devices | AUG 059. Some scanners will only use these bytes when polling for and displaying information via the Modbus TCP protocol. The telegram functions 03H (Read Holding Register) and 10H (Preset Multiple Registers) e. In the MODBUS protocol, the master requests function execution to the slaves. Modbus library. 2 days ago · Modbus Exception Codes Supported Code 01 Illegal Function (sent in response to a Master device use of a Function Code other than Code 3) Code 02 Illegal Data Address (sent in response to a Master device query outside of the allowable register range) Modbus protocol defines several function codes for accessing Modbus registers. Select whether or not to log writes from the master to the slave. The Modbus Master Source Code Library (SCL) is an attempt towards assisting Original Equipment Manufacturers and HMI Software vendors in quickly implementing Modbus support into their devices/products. 1 Use of the manual The manual is part of the product and contains important information on operation and. • Modbus ASCII was the first Modbus and is a serial protocol, typically running on either the RS-232 or RS-485 physical layer. I use this library… I have no made any modification to the code: Github user 4-20ma “Modbus Master” see the modbus master files inside src folder, notice I copy crc16. The modbus_read_registers() function shall read the content of the nb holding registers to the address addr of the remote device. dll, Function Code: 15, Exception Code: 9 And in the line: master. Visualizing Data in the Modbus Device. Valid addresses for this type of data are: X3XXX i. Modbus Program User Manual SECTION 1 Š GETTING STARTED 1. hi, you can found modbus protocol at www. c 3 //// - Wrapper to respond to 0x16 (read coils ) in the MODBUS specification. Through the verification and analysis of experiment, Modbus-S can fully compensate for the design defects of Modbus TCP protocol. Refer to the section below for details. Added additional function codes 06(write single register) Added exception codes 03h(illegal address) and 04h(illegal data value) Deleted the modbus registers 0xE0E0 and E0E1 which are not required. means device operating as master will poll one or more device operating as slave. Other functions, such as file read and diagnostics functions also exist Undocumented Modbus function codes can also be used to perform specific actions Function name Function code Read coils 1 Write single coil 5 Read holding registers 3 Write single register 6 Write multiple registers 16 Read/Write multiple registers 23. 3 Message Function Codes The IR5500 Modbus interface supports the following standard function codes for communication with external instruments: Function code 03 (Read Holding Registers) for reading single or multiple registers;. Exception One: Register #24 (Modbus Register #25) Drive Status, can also be read as a group of 6 words. See FPS Manual Appendix E for the Modbus register list and address definitions. VB2010 Express is available as a free download (for evaluation purposes) from Microsoft. A large number of devices have the TCP/IP modbus protocol becoming one of the most commonly used protocols at industrial level, this time we created a routine for ESP8266 as a slave Mobdus TCP/IP, we created this routine based on this Example Update ESP8266 Industrial Modbus TCP IP V2. This example code shows a quick and dirty way to get an arduino to talk to a modbus master device with a device ID of 1 at 9600 baud. function code One of numerous functions defined within th e Modbus specification, of which a device may implement. Function codes. The receiving. Number of stopbits is fixed to 1 All TAC5 data is in 16 -bit modbus holding registers. MODBUS exceptions do not cover the application level, i. Function codes 3 and 4 are treated the same by the S7810M. This command is requesting the content of analog output holding registers # 40108 to 40110 from the slave device with address 17. Since the RS485 has a two-wire interface (half-duplex), writing and reading must be conducted consecutively. Use zero based address, e. Do you want to unsubscribe in order to stop receiving notifications regarding "Modbus RTU Master Implementation; GUI - demo" changes. • Direction of data transmission (master → slave or slave → master). 4 Modbus functions are available: • 3 (16#03) Read Holding Registers • 6 (16#06) Write Single Register • 16 (16#10) Write Multiple Registers • 43/14 (16#2B/0E) Read Device Identification Function 3 has a restricted implementation: • with length 1 it permits to read any parameter of the drive, one by one, see page 33. The Modbus extension supports the following Modbus functions: Read Coils (function code 1) Read Discrete Inputs (function code 2) Read Multiple Holding Registers (function code 3) Read Input Registers (function code 4) Data conversion rules. The function only adds to the message, the header or CRC of the selected backend, so raw_req must start and contain at least a slave/unit identifier and a function code. Each message comprises three parts: modbus application header, function code and data. codes is presented in Table 2. The Modbus standard makes use of the EIA RS 485 standard. Code Function Data Access Description 0x01 Read Coil Bit access. 6 2 ModBus Conﬁ guration MODBUS / BACnet Exception Codes Code Name Meaning 01 ILLEGAL FUNCTION The function code received in the query is not an allowable action for the server (or slave). 0, Visual C++ 6. 01 February 23, 2004. uModbus implements both a Modbus client (both TCP and RTU) and a Modbus server (both TCP and RTU). For example, MODBUS assumes a register is a 16-bit entity, so any value between 0 and 65535 (decimal = FFFF hex) is valid to be written to / read. 03: The Function Code 3 (read Analog Output Holding Registers) 06: The number of data bytes to follow (3 registers x 2 bytes each = 6 bytes) AE41: The contents of register 40108 5652: The contents of register 40109 4340: The contents of register 40110 49AD: The CRC (cyclic redundancy check). uModbus or (μModbus) is a pure Python implementation of the Modbus protocol as described in the MODBUS Application Protocol Specification V1. 11: The Slave Address (11 hex = address17 ) 06: The Function Code 6 (Preset Single Register). Modbus Function Code: 1, 5, 15 Modbus Start Address: 4001 Modbus Block Size: 500 Number of Blocks: 1 Primary use: Clear min/max registers on command. If you are interested in developing a Modbus Master application, here are some programs that I wrote that you can extract code from. Modbus Function Codes The last two bytes are the CRC pattern. REGISTER READING (0x03) Format of command sent by the Master: - Device address: Address of slave device to be polled - Function Code:. 469 MOTOR MANAGEMENT RELAY – COMMUNICATIONS GUIDE 5 Modbus Functions Supported Functions The following functions are supported by the 469: Modbus Function Code 01: Read Relay Coil Modbus Function Code 02: Read Digital Input Status Modbus Function Code 03: Read Setpoints and Actual Values Modbus Function Code 04: Read Setpoints and Actual Values. 7200MA MODBUS Application Notes A C D 6/29 7200MA MODBUS MANUAL. means device operating as master will poll one or more device operating as slave. This count is identical to that returned by the Diagnostic function (code 08), sub-function Return Bus Message Count (code 11, 0B hex). h header file includes more function code definitions, such as: • ReadCoil 1 • ReadDiscreteInputs 2 • WriteSingleRegister 6. Modbus technically only supports 6 different I/O types, force / read coil, read input status, read / write holding register and read input register. MVI56-MCM ♦ ControlLogix Platform Contents Modbus Communication Module User Manual ProSoft Technology, Inc. the crc generation is easy. In server mode the memory areas of several TwinCAT runtime systems can be mapped directly to the Modbus memory areas. Modbus was always capable of 64k register addresses that requires what was called 6 digit addressing: (4)xxxxx. Therefore, a complete definition of where to find a piece of data requires both the address (or register number) and. This may be because the function code is only applicable to newer devices, and was not implemented in the unit selected. 4 Holding (READ FROM / WRITE TO) registers (Modbus function codes 3 & 6) 30 5. Two Modbus functions are currently supported: Read Holding Registers. To toggle the LED, it must send a Modbus message to slave address 1 that writes a single holding register (Modbus function #6) to the first element with a value of 0 or 1. The data registers are always 16 bit (two byte) values, transmitted high order byte first. 3 or later For Simplex and Redundant Applications USER MANUAL. Function Field Valid function field codes are in the range of 1 - 255 decimal. The code i've found about MX2 VFD from another person is the above:. Function Code untuk umum. Function code 6 is used to write a single holding register. The parameter contains one byte of information. This Operation Manual explains the serial communication (Modbus), among others, providing the. A large number of devices have the TCP/IP modbus protocol becoming one of the most commonly used protocols at industrial level, this time we created a routine for ESP8266 as a slave Mobdus TCP/IP, we created this routine based on this Example Update ESP8266 Industrial Modbus TCP IP V2. The Modbus RTU XDriver supports special function codes to convert various (Non Modbus standard) data formats for use in Continuum points. Modbus-S is a Modbus Slave (server) software component enabling an embedded system to communicate to a Modbus Master (client). At the word level, Modbus function code 4 (read input register) or Modbus function code 3 (read holding register) can be used. Modbus/TCP, also known as Modbus TCP/IP, is a form of Modbus that uses the TCP/IP layers as a base for controlling the communications between different devices. 2 Target Audience. Visualizing Data in the Modbus Device. We can see, although the Holding Register is the same, in read, the function code is 0x03, in write, the function code is 0x06. Modbus Function Code 6.