What register information should be specified in Modbus communication of air conditioning box?

Modbus communication of air conditioning boxes should clearly define the physical or network interface, protocol form, address, register number, function code, data type, scaling, byte order and read and write restrictions. Just because both sides support Modbus, it does not mean that the same register address or numerical interpretation will automatically be consistent.

Use a temperature point to check if the data definition is complete

The temperature may be expressed as an integer multiplied by a coefficient, or it may be expressed as a floating point. The sign of negative values ​​and the order of multi-word data also need to be clear. The display number in the register file and the actual message address may also use different starting points, which should be confirmed through joint debugging. The serial port solution also needs to match the baud rate, verification and wiring requirements, and the network solution needs corresponding network parameters.

The connection parameters need to write the interface, site or network address and communication settings; the data parameters need to write the address, function code, type, scaling and byte order; the control parameters need to write read and write permissions, command conditions and communication failure strategies. The three items correspond to different configuration links and cannot be given just one register number. Please refer to the table of points that need to be provided before the air-conditioning box is connected to the building automation system.What point tables need to be provided before the air-conditioning box is connected to the building automation system?。

The physical interface and communication parameters must be confirmed first

Modbus can run over a serial port or network. The serial port solution usually requires confirmation of the interface form, baud rate, data bits, stop bits and verification method; the network solution requires confirmation of the IP address, port and connection method. The default parameters of different devices may be different, and communication parameter tables should be exchanged before docking.

What is the difference between the BACnet interface of the air conditioning box and the dry contact linkage? Please refer toWhat is the difference between the BACnet interface and dry contact linkage of the air conditioning box? . For control point table and signal definition, please refer toWhat point tables need to be provided before the air-conditioning box is connected to the building automation system?。

Register address and function code must be defined in pairs

Each data point should clearly identify the register number, function code and read and write attributes. The address ranges of holding registers, input registers and coils are different, and the function codes are also different. If you only give an address number without specifying the register type and function code, you may read the wrong location or read and write direction during docking.

The register document should also indicate whether the address starts from 0 or 1. Different software tools may display it differently. Read and write permissions should be distinguished between read-only, write-only and read-write. The write command should also specify the valid range and conditions.

Data type, scaling and byte order cannot be omitted

The same register value can represent an integer, an unsigned integer, a floating point number, or a bit state. Analog quantities such as temperature, humidity, and pressure often require scaling factors and offsets. Multi-word data (such as 32-bit floating point) needs to specify the word order and byte order, otherwise the read value may be very different from the actual value.

Negative values ​​and alarm bits also need to be clearly coded. Alarm status may be represented by bits or integer values ​​representing different fault types. If the data type and encoding method are not clearly written, it is easy to misjudge normal values ​​as faults during joint debugging.

Write commands and protection logic must be written clearly

If the upper system needs to remotely start and stop or adjust the setting value, the address, data range, validity conditions and priority of the write register should be clearly defined. The switching logic between local control and remote control, the default state when communication is interrupted, and write timeout processing all need to be agreed in advance.

Important protection usually requires a hard loop independent of communication, please refer toWhat is the difference between the BACnet interface and dry contact linkage of the air conditioning box? . Writing commands cannot replace independent protection such as emergency stop, fire linkage or antifreeze protection. Scenarios such as normal writing, illegal writing, and communication interruption should be verified during debugging.

Joint debugging cannot only verify that one number has been read

The actual physical values, reading and writing directions, alarm changes and recovery behaviors should be checked to avoid data format errors but appearing as seemingly reasonable numbers. Write tests must be performed under agreed test conditions and comply with local priority and protection logic. The register version and test records confirmed by both parties will be retained in the end.

How to change the debugging sequence from stand-alone to system linkage, please refer toHow to change the debugging sequence of air conditioning box from stand-alone unit to system linkage? . Whether the sensor readings are reliable, please refer toHow to determine the installation and calibration requirements for air conditioning box temperature and humidity sensors?。

Aili industrial supporting equipment

Aili Industrial's control docking can be carried out around the confirmed register table. Please explain the upper system and interface requirements before accessing to facilitate point-by-point verification. Aili's industrial manufacturing end covers the independent research and development and production of motors and fans, control systems, sheet metal, air filters and complete machine assembly. The controller interface, register definition and box structure can be corresponded in the same set of supporting materials; non-standard communication requirements can be adjusted according to the project docking document.

Product form can be viewedAir handling unit andFan box page; clean air supply package can be combinedFFU fan filter unit andEFU equipment end fan filter unit verification; multiple equipment linkage can understandMatching method of FFU computer group control system ; terminal particle filtering can be combinedHEPA/ULPA filter confirmation; when it comes to gaseous pollution control, you can communicate separatelyChemical filter solutions. The specific register definition, communication parameters and delivery scope still need to be confirmed based on the corresponding configuration data and on-site joint debugging results. The actual effect is subject to on-site joint debugging and performance test results.

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Related questions and answers

Both sides support Modbus, so are the register addresses the same?
uncertain. The address, function code, data type and scaling may be different. The register table should be exchanged and checked point by point before docking.

The temperature value reads a very large or very small number, what could be the reason?
It may be that the data type, scaling factor or byte order is inconsistent. You should check the register definition first and then determine whether the sensor is abnormal.

Can Aili Industrial provide the register table?
Device-side register definitions and communication parameters can be provided according to project control requirements. The specific content needs to be confirmed based on the selected controller and project docking files.

Related articles

1. What point tables need to be provided before the air-conditioning box is connected to the building automation system?

2. What is the difference between the BACnet interface and dry contact linkage of the air conditioning box?

3. How to change the debugging sequence of air conditioning box from stand-alone unit to system linkage?

4. How to determine the installation and calibration requirements for air conditioning box temperature and humidity sensors?

Key points for selection and acceptance inspection