Function 02 modbus. Aug 29, 2023 · Function code 0 is not valid. Read Scattered Holding Register Example. Its main features are: Compact size. Thank you. The following table shows how to read the rms current on phase 1 (I1) in register 1016. 1 byte. Modbus Plus Network Planning and Installation Guide. Oct 24, 2023 · There are a collection of modbus nodes available for node-red which you will need to install. Introduction. di_read: Function Code 03: modbus. The S7-1200 CPU is Modbus TCP server. Therefore, it is not necessary for the “read” command function 02 to specify the first digit of the register address. 11 05 00AC FF00 4E8B. 0B: The Slave Address (0B hex = address 11). Both channel types are displayed in the left column of the tab. Provided the data logger has a working network connection, further troubleshooting can be done with a computer running Modbus Feb 9, 2023 · Modbus Function Codes. Previously referred to as a master-slave protocol, the Modbus organization replaced the terms master and slave with server and client in 2020. Modbus: 0 Sep 11, 2018 · Modbus Function Code: Lua Function in MPM: Function Code 01: modbus. May 22, 2019 · 2. coil_read: Function Code 02: modbus. Through the Modbus-TCP interface you can read and write data to the chargers, battery monitors, inverter/chargers and Nov 19, 2023 · 2023-11-19. After receiving a query message with Modbus function 02, the slave puts the requested input values in a message structure and sends this message back to the Modbus master. Force Single Coil (Function Code=05) Request. Feb 1, 2020 · Based on the rigor of @maxy's answer, then on @Brits's answer, I decided to investigate further. The length of the message depends on the number of input values returned. all the addresses beginning with the digit “1”). Specifically, it covers the use of Modbus messaging in an intranet or internet environment using the TCP/IP protocols. We will also explain in detail the main types of function codes you will use typically. 02: The Function Code 2 (Read Discrete Inputs). Apr 19, 2022 · Nessa aula vamos analisar a descrição dos principais códigos de funções que compõem o protocolo Modbus. 02/13 Modbus® RTU Serial Communications User Manual 1 1. 1) that provides Modbus TCP/RTU server and client implementations for easy process data exchange. org). It is especially useful in embedded and resource-constrained systems like microcontrollers. so function code is a must have. GM–BM85–001. Reading input values with Modbus is done in the same way as reading the status of coils. Figure 6. The possible codes are shown in the table below. Modbus over serial line V1. "0" = No multiple message transaction or the end of the multiple message transaction. Provided the data logger has a working network connection, further troubleshooting can be done with a computer running Modbus Description. Aug 30, 2006 · new MODBUS solution over serial line should implement an electrical interface in accordance with EIA/TIA-485 standard ( also known as RS485 standard). The command to turn on, according to the manual, looks like 01 06 00 01 01 00 D9 9A Modbus function 0x16 Mask Write Register. If the NAU does not appear in the list box, wait until it broadcasts (10-15 minutes). 02,” on Modbus. Go the the menu and select manage Palette and search for the node-red-contrib-modbus package. Modbus RTU Frames Jan 23, 2021 · Modbus TCP Protocol. the address of the first input specified, and the number of inputs. Ich habe versucht die Modus Kommunikation am Chint DTSU sowie direkt am Wechslerichter abzugreifen. In this example, two Modbus functions are connections. The socket returned from TCPOpen () should be a number less than 99. Mit verschiedenen Modbus-TCP Modulen sowie einem Serial-USB Adapter. coil_write: Function Code 06: modbus. In modbus-tk Issue #121, the OP mentions that pymodbus worked with function code 23, read/write multiple registers. This is an obsolete Modbus specification, should only be used to address legacy issues. Number of Bytes. TxData[1] = 0x04; // Function code for Read Input Registers. Each bit is sent as a voltage. Modicon, Inc. Jan 24, 2013 · Function code: 22 (0x16) Mask Write Register. We are experts in Modbus RTU/TCP communication and carry a wide variety of Modbus products: Modbus Stack. Request for basic information. Therefore, the rms current on phase 1 (I1) is 555 A. So libmodbus is just sticking to the Modbus specification. com Dec 13, 2018 · This function code is used by TOP Server when requesting a read of one or more (up to 2000 at a time) output coils or 0xxxxx type discrete/boolean addresses. payload; const buf = Buffer. Output coils are read/write access - you'll see support for Function Codes 5 and 15 a further down the list. The function code that operates on this register specifies a "holding register" operation and the "4xxxx" reference group is implied. You can only query the value of inputs of one device at a time. Definition. The exception code gives an indication of the nature of the problem. hr_write Dec 10, 2019 · All Modbus function codes follow a similar pattern to the two examples shown above. The function can be used to set or clear individual bits in the register. Sep 19, 2022 · There is a two-channel relay with Modbus, I use the package to communicate with it node-red-contrib-modbus Read channel 1 and channel 2 state ：01 03 00 01 00 02 95 CB — it is not problem The problem starts when I initiate the write, namely. 02; Modicon Modbus Protocol Reference Guide (hay MODBUS Over Serial Line FOR LEGACY APPLICATIONS ONLY, theo tên gọi của Modbus Organization): Tài liệu 121 trang; 1996. The following table describes the exception codes handled by the circuit breaker: Exception Code. Speed up your PLC programming with this simulating tools. 3 Function Field The Modbus functions implemented in the PowerSmart+ Advance meter are shown in Table 2-1. The slave may be in the wrong state to process a specific request. Bit Name Description; 0 "Extended" flag: This bit is used if the object dictionary data set is larger than would fit in a Modbus command. This function code is used to modify the contents of a specified holding register using a combination of an AND mask, an OR mask, and the register's current contents. The request specifies the holding register to be The FX5 MODBUS/TCP communication function allows communication, via Ethernet connection, with various MODBUS/TCP master devices which are connected to FX5 set as the slave station. We will see how exceptions are conveyed further in this tutorial. For more information consult the Modbus specification. The supplier must specify: Support for RS-232 and/or RS-485 and wiring instructions Support for RTU and/or ASCII modes Speed, data bits, stop bits, parity The supplier must provide customer-quality user documentation to assist the tester with setup instructions. This command is writing the contents of discrete coil # 173 to ON in the slave device with address 17. Let’s consider an example where a PLC reads 1 input register 30100 from a device (ID 2) The PLC will transmit the following sequence in Modbus RTU (Hex). See full list on control. MODBUS fc01 fc02 fc03 fc04 fc05 fc06 fc15 fc16 ASCII TCP exceptions About Enron MODBUS RTU Master RTU Slave TCP Client Download Purchase Contact . Data contained with any open document is accessible to the master application. The Omron CP1H and CP1L PLCs offer a built in function called ‘Easy Modbus’, that performs a Modbus RTU Master function, allowing the PLC to communicate with devices that use the Modbus RTU protocol, such as inverters, scales, temperature controllers, etc. The process to read the input Registers is similar to the Holding Registers. Không vì chúng được đẩy bởi một nhóm lớn các nhà cung cấp hay một tổ chức chuẩn đặc biệt. The request PDU consists Dec 30, 2019 · Funtion Code별 DATA 구조 및 디바이스 제어. read failed: modbus: exception '2' (illegal data address), function '3' Dec 20, 2006 · new MODBUS solution over serial line should implement an electrical interface in accordance with EIA/TIA-485 standard ( also known as RS485 standard). MODBUS Lịch sử của Modbus protocol Vài chuẩn truyền thông vừa nổi lên. That is 83H, and fill 02H into Exception Code then send it back to Master equipment. MODBUS-TCP는 Function Code별 프로토콜 Data구조가 조금식 달라집니다. Jan 4, 2019 · Modbus 07 and 08 function codes and sub-codes can be used to get additional diagnostic information on serial links (see “MODBUS over Serial Line Specification and Implementation Guide, V1. You can access the coils, inputs, holding, read registers from your devices as sensors, switches, selects, numbers or various other ESPHome components and present them to your Analysis of modbus query: 05 03 1000 0002 E6: is the starting character ; 05 is the slave address of the PLC ; 03 is the function code (03 = “Read Register”) 1000 is the starting address (relative address 0x1000 = 4096 decimal = absolute address 44097 decimal) 2. No dynamic memory allocations. Now internally on the VFD, Coil 1 - Run/Stop Command and Coil 2 - Forward/Reverse Direction may both be mapped to individual bits of a single 16-bit control word Feb 3, 2003 · For example a sample command request might be: 0203 9C66 0001 4A76 where 02 = Modbus Unit Address 03 = Read Function 9C66 = 40038 = Starting Register 0001 = # of registers to read from 4A76 = CRC and the return string (Read Holding Registers) might look like: 0203 0200 00FC 44 where 02 = Modbus Unit Address 03 = Read Function 02 = byte Count Use Type "Modbus" and set the Analyzer Id property to the NAU’s analyzer id. The Modbus RTU allows the instrument to be a citizen on a Modbus is a serial communication protocol developed by Modicon, published by Modicon® in 1979, for use with programmable logic controllers (PLC). Table 2-1 Modbus Function Codes Code (decimal) Meaning in Modbus Action 03 Read holding registers Read multiple registers 04 Read input registers Read multiple registers Modbus Specifications and Implementation Guides. 02 - Device ID; 04 - Function Code for Read Input Register Sep 6, 2018 · The data to be sent to the 3rd party Modbus device is held in a manual array in the AnnexPoint not the X Driver point itself. The following table shows how to read the addresses of the register 664 (address 0x0297) and register 666 (address 0x0299) of a Modbus slave. 1 MODBUS Master / Slaves protocol principle Function code Data MODBUS PDU Figure 5: MODBUS Protocol Data Unit Apr 27, 2023 · Es ist ein Chint DTSU 666 verbaut. . Please direct all support questsions to slack or the forums. All addresses and the general function are tested with another Modbus client. The address of register 1016 is 1016 - 1 = 1015 = 0x03F7. 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) 04 Read Input Registers (when addressing The slave's response for these functions will contain the Slave's address (1 byte), function code (1 byte), register address (2 bytes), register value (2 bytes), and a CRC (2 bytes). The goal of this series is to give an overview of the specification and to demonstrate how it can be used for basic use cases. If you are choosing a Control Solutions I/O device, pick one that matches your network. The nodes that we are mainly interested in are the read and write nodes. CRC Calculation Explanation Feb 6, 2020 · When I use function code 0x04 (read input registers) to read all 8 registers simultaneously, the request succeeds. Modbus Coil - Information contained as a 1-bit quantity. 7. If you are looking for a Control Solutions gateway, you will need to pick the model that matches the electrical interface of the equipment you want to connect. msg. Namely, these are: Note: The Modbus clients implement each function code This command is requesting the content of analog input register #30011 from the slave device with address 11. The function code received in the request is not an authorized action for the slave. In simple words, it is a method for transmitting information over serial lines between electronic devices. Modbus Scanner. Value. In addition, some devices may implement a “Four-Wire” RS485-Interface. 3. Oct 1, 2022 · Reading Input Registers. ----- Sep 6, 2023 · In Modbus RTU, function code 01 represents a read from multiple coils operation, 05 corresponds to writing a value to a single coil, 02 initiates a read from a discrete input, 04 lets the client read an input register, and function codes 03 and 06 let a client read and write holding register values. Conclusion. 0B: The Slave Address (0B hex = address 11) 04: The Function Code 4 (Read Input Registers) 000A: The Data Address of the first register requested (000A hex = 10, + 30001 offset Modbus Transmission Example 1 - Read Input Register. Following the Function Code is the Exception Code. 02 – Modbus Organization (2006) Modicon Modbus Protocol Reference Guide – Modbus Organization (1996). 1 Modbus RTU Implementation This implementation is designed to provide a popular data exchange format connecting these instruments to both Honeywell and foreign master devices. The data is sent as series of ones and zeroes called “bits. Show QR code for this page. 01 (0x01) Read Coils 02 (0x02) Read Discrete Inputs 03 (0x03) Read Holding Registers 04 (0x04) Read Input Registers 05 (0x05) Write Single Coil 06 (0x06) Write Single Register MODBUS RTU Function Codes The following MODBUS RTU functions are supported by the T1K–MODBUS base controller. So you can not use that. The data is sent as series of ones and zeroes called bits. The simplest setup would be a single serial cable connecting the serial ports on two devices, a Client and a Server. 6 XL and GE iFIX 5. The data set then spans over multiple Modbus messages; each message contains part of the data set. For Modbus TCP, it indicates a failed socket connection. B053: The CRC (cyclic redundancy check). Modbus Function Code 2 (Hex 0x02) 984 Programmable Controller Systems Manual. Name. Dec 4, 2023 · Modbus communicates over several types of physical media such as RS-232/RS-485 or Ethernet. 02 (0x02) Modbus Serial only. Function Code별로 요청·응답에 대한 프로토콜의 데이터 구조를 알아보고 TCPPORT의 디바이스를 제어하는 방법을 살펴 보겠습니다. Figure 3. If everyone have any questions please ki Bit Name Description; 0 "Extended" flag: This bit is used if the object dictionary data set is larger than would fit in a Modbus command. Other. The simplest setup would be a single serial cable connecting the serial ports on two devices, a Master and a Slave. The request specifies the holding register to be written, the Mar 24, 2021 · Modbus TCP has Format Slave ID; Function Code; Adress, num of coils. The only change is instead of using the function code 3, now we use the function code 4. Therefore, it is not necessary for the “read” command function 02 to specify the first digit of the register address. Nov 2, 2019 · SunSpec Tutorial Part I: Modbus. Whether you are connecting via Modbus to a solar inverter, power meter, or flow meter, the information provided here can help you overcome the challenges, and successfully gather data into a Campbell data logger. Client and server code can be disabled, if not needed. Refer to the following publications for details about the application and installation of the Modbus Plus network and related communications devices: GM–MBPL–001. 1. Return value. A distinction is made between generated channels and user-defined channels. Figure 6 shows a list of the common function codes along with exception codes for exception responses. 0 Tài liệu về phiên bản cũ hơn của MODBUS over Serial Line V1. Function 01 answer structure Function 02: Read input status. The device identification data consists of ASCII characters called objects. So I know that address and conn Apr 13, 2017 · I have a gateway communicating to 3 Modicon Quantum PLCs. The modbus_controller component creates a RS485 connection to control a Modbus server (slave) device, letting your ESPHome node to act as a Modbus client (master). The function code field of a MODBUS data unit is coded in one byte. Zeroes are sent as positive voltages and a ones as negative. The Request PDU specifies the starting address, i. in_read: Function Code 05: N/A: Function Code 15: modbus. Thus, holding register 40108 is actually addressed as register 006BH (107 decimal). Hi, I am trying to get data from my SMA Solar Inverter. 007A: The Data Address of the first input to read (00C4 hex = 122, +10001 offset = input Nov 9, 2020 · In the modbus device dtm you should be able to specify function codes, rep rates or trigger types etc which then GENERATES the modbus table in the NOC/CPU in the same way a VSD DTM does. Description. The only difference is that for inputs Modbus function 02 is used. 01 (0x01) Illegal function. “This function code is used to read from 1 to 2000 contiguous status of discrete inputs in a remote device. Introduction 1. Figure 3 shows an example of function code 05 from the Modbus Application Protocol specification, which does not contain the slave address or the CRC. Modbus Relative Addressing. The S7-1500 CPU establishes the first connection as Modbus TCP client. This standard allows point to point and multipoint systems, in a “two-wire configuration”. Modbus. Các chuẩn này—giống Modbus interface—nổi lên vì chúng tốt, đơn giản để thực hiện và do đó For Modbus TCP, it indicates a failed socket connection. Tài liệu hiện tại đã lỗi thời và chỉ được tham The MODBUS application protocol establishes the format of a request initiated by a client. 3 Function Field The Modbus functions implemented in the Multi-Mon/036 are shown in Table 2-1. FluentModbus is a . If you agree to the terms herein then you must click the "I ACCEPT" button below before you are permitted to use this software/protocol and related documents. For example, Modbus function code 02 reads discrete input registers in the device with an absolute address range of 10001 to 19999 (i. Table 2-1 Modbus Function Codes Code (decimal) Meaning in Modbus Action 03 Read holding registers Read multiple registers 04 Read input registers Read multiple registers Modbus TCP/IP (sometimes referred to as the Modbus TCP protocol or just Modbus TCP) is a variant of the Modbus family of simple, vendor-neutral communication protocols intended for supervision and control of automation equipment. Only ~1500 lines of code. Slave number. Jan 16, 2003 · Modbus Function Code 5: Modbus: 2: Jan 14, 2021: Concept 2. Generated Channels are automatically generated from the created variables Structure of Modbus Read Device Identification Messages. You can first save the two integers to a buffer (swapping the words as you mentioned in the OP). The "MB_SERVER" instruction processes connection requests of a Modbus/TCP client, receives requests from Modbus functions and sends response messages. Broadcast addressing mode is not supported. The value 0xFF has to be used. Modbus-TCP is an industry standard protocol, that can be used to interface PLCs or other third party equipment with Victron products. The modbus_free() function shall free an allocated modbus_t structure. Now that you understand what Modbus functions are, and how they’re used to interact with registers in the server, let’s get into the details of the 8 most popular Modbus functions. address, function code, data field and error-checking field. Query - A Modbus message from the Modbus master to the product. This is how the function node will look like (first line added for testing purposes). Modbus TCP is basically the Modbus RTU protocol with a TCP interface running on Ethernet. . Each discrete input is a single bit. "1" = Part of a multiple message transaction. Chipkin has Modbus solutions for almost every situation. Modbus Slave. Modbus is used for transmitting information between devices that are connected to buses or networks over serial lines or Jan 14, 2021 · From a Modbus perspective, if a client/master wants to command this theoretical VFD to run, it would send a Function Code 5 request to the VFD to write Coil 1 - Run/Stop Command to ON. This is a three-part tutorial about SunSpec, an open specification that aims at increasing the interoperability within the solar and distributed energy industry. I’m guessing my PLC type does not support a specific modbus function, but I have only seen that before with writing to bits or coils, not 12/02/02 2 MODBUS Data Link Layer 2. 02 04 00 63 00 01 C1 E7. Afterward, read the buffer as a float. Modbus Gateways. Use Type "Modbus" and set the Analyzer Id property to the NAU’s analyzer id. Any device can be a client or a server. Implement Modbus function code 02. The content of register 1016 (address 0x03F7) is 0x022B = 555. Each register contains 16 bits. 0xFF. when the communication parameters are modified. Download PDF. The console log is throwing 39,357 errors per hour currently with Logger ReadHoldingRegistersRequest and ReadCoilsRequest, with message Received response with ExceptionCode: 0x01 (IllegalFunction). Originally implemented as an application-level protocol intended to transfer data over a serial layer, Modbus has expanded to include implementations over serial, TCP/IP, and the user datagram protocol (UDP). 3. The request specifies the holding register to be written, the Feb 24, 2012 · For example, holding register 40001 is addressed as register 0000 in the data address field of the message. The CJ1 / CJ2 / CS1 PLCs support Modbus through a Protocol Macro. com; Modbus tutorial at RF Wireless World Nov 24, 2020 · 11: The Slave Address (11 hex = address17 ) 04: The Function Code 4 (read Analog Input Registers) 02: The number of data bytes to follow (1 registers x 2 bytes each = 2 bytes) 000A: The contents o avoid multiple use of functions 3 and 4 in order to read non-contiguous registers. TxData for Input Register query. allocUnsafe(4); Oct 31, 2019 · That FF you see right before the Modbus function is actually correct. Oct 17, 2018 · Modbus is transmitted over serial lines between devices. If you have a failed socket connection for Modbus TCP, check your TCPOpen () instruction. This causes the length of the output message to vary. Quoting the Modbus Implementation Guide, page 23: On TCP/IP, the MODBUS server is addressed using its IP address; therefore, the MODBUS Unit Identifier is useless. This command is requesting the On/Off (0/1) status of discrete inputs # 10123 to 10150 from the slave device with address 11. When I use function code 0x04 to read the registers, either individually, or as a partial group (ex: only the first 7 of 8), the sensor returns an exception code 2 ( illegal data address ). Overview. List of Public Modbus Function Codes Function Code Jul 27, 2022 · Hello everyone!In this video I would like to show and share about PLC S7-1200 Modbus TCP/IP all function code Part-1. There is no return values. name: power slave: 1 Function: 2 address: 1002 coils: 5; that is the goal. This article introduced Modbus. Modbus Slave is for simulating up to 100 slave devices in 100 windows!. This function code is used to modify the contents of a specified holding register using a combination of an UNSELECTED mask, an SETBIT mask, and the register's current contents. 5 IGS OPC - "Illegal Modbus Function Call" Programmable Logic Controller - PLC: 0: Oct 8, 2020: G: MODBUS Function Code 16 - Value out of range: Modbus: 2: Sep 9, 2019: E: Function Read File Record (function code - 0x14) in Modbus Protocol Specification. The “Modbus Communication Channels” tab displays which Modbus channels/function codes can be used to read and write variables. Valid codes are in the range of 1 255 decimal (the range 128 – 255 is reserved and used for exception responses). RS-485 Connections 1. 0A: The Slave Address ( 0A hex = address10 ) 81: The Function Code 1 (read Coil Status - with the highest bit set) 02: The Exception Code. Define the Start channel address; Enter the number of Bits to be written in the "Number Of Channels" Jun 18, 2009 · Section 1. nanoMODBUS is a small C library that implements the Modbus protocol. NET Standard library (2. The best example of how this should be implemented is in the Generic Modbus device in EcoStruxure Machine Expert. Modbus for Field Technicians at modbusbacnet. see About Modbus TCP | Simply Modbus Software Modbus function 0x16 Mask Write Register. Function codes from 128 to 255 are reserved for indicating exception conditions. Response - A Modbus message from the product to the Modbus master. November 2, 2019. Function 04 can be used in the same context as function 03. Modbus TCP uses Ethernet. 2. Read Coils (Code 01) A Modbus client uses this function to read the values of coil registers within the Modbus server. The following functions are supported by Modbus Poll. There are 11 nodes in the package and they are grouped together in the Modbus section. Modbus function code categories Data Modbus Integration Solutions. Mar 31, 2023 · Modbus is an industrial protocol that was developed in 1979 to make communication possible between automation devices. Data send to ip: 01 02 03 ea 00 05. 0 and 2. Like Modbus RTU, Modbus TCP operates on a client/server principle, but in this case, the client (master) initiates both requests and responses from a server (slave). Resetting Counters. • The master function and slave function are supported and the master and slave can be used simultaneously by a single FX5. Function Codes and Exception Codes . The Modbus address of the Modbus slave is 47 = 0x2F. Both, the server and the client, implement class 0, class 1 and class 2 (partially) functions of the specification. Start programming and test before you receive your slave device from supplier. Modbus Data Clients. Modbus Weather. hr_read (16-bit) Function Code 04: modbus. Jul 14, 2023 · edited. TxData[0] = 0x05; // slave address. The device requesting information is called Modbus Master and the devices providing Function 83 H Exception Code 02 H CRC Lo 81 H CRC Hi 30 H Remark：Address 0020H is illegal for Function Code: 03H , Therefore Slave equipment will set the MSB bite of Function Code: 03H as 1. Modbus Tools. 02 (0x02) Most of the difficulties with Modbus communications arise from deviations from the standards, which are not enforced within Modbus. MODBUS FUNCTIONS Modbus is a data communication protocol that is based on a request-response model. Use the Gas Chromatograph Portal to make entries in the "sending analyzer" result table to indicate which component values to send. payload = [0, 16833]; let pay = msg. Modbus RTU uses RS-485 or RS-232. The goal was to identify if the root cause was a modbus-tk bug, or if my device doesn't support function code 23. Modbus Register - Information contained as a 16-bit quantity. Create an X Driver point on the required Comm port and define: The correct slave number; Function code 15. The original Modbus interface ran on RS-232 serial communication but most of the later Modbus implementations use RS-485 because it allows for longer distances, higher speeds and the possibility of multiple devices on a single multi-drop network. 11: The Slave Address (11 Jul 27, 2022 · Modbus is transmitted over serial lines between devices. Request frame breakdown. e. Modbus Read Discrete Inputs (02) Modbus Read Holding Registers (03) Modbus Read Input Registers (04) Modbus Write Single Coil (05) Modbus Write Single Register (06) Modbus Write Multiple Registers (16) Modbus Read Coils (01) Modbus Read Coils, function code 01, reads between 1 and 2000 output coils (bits) from the PLC. ”. Ich erhalte immer die Fehlermeldung. MODBUS-TCP는 서버로 사용되며 IP Function Field. 0B 04 000A 0001 1162. Modbus-TCP is a feature on all our GX devices eg Cerbo GX, and Venus GX . The counters are reset to 0: when they reach the maximum value 65535, when they are reset by a Modbus command (function code 8, sub-function code 10), when the power is cut off, or. The Function Code field tells the addressed slave what function to perform. Please review the following license agreement before down loading any MODBUS protocol or related documents from this web site. up rj sc pq pr ne ng an ga xy