Communication Structure; Modbus Rtu Airzone - Airzone Modbus Bedienungsanleitung

Communication
structure

MODBUS RTU AIRZONE

Note: Available for Airzone systems, Webserver and Aidoo Pro.
The format of the commands for read/write operations with Modbus RTU (8 bytes) is as follows:
System address Operation code
1 byte 1 byte
◊
System address. Defines the system to be accessed. Addresses are from 1 to 247, as address
0 is reserved for transmission to all devices (Broadcast).
◊
Operation code. Indicates the function to be performed by the command.
◊
Zone address. For zone commands, this field defines the zone to which the operation is
carried out. For system commands this byte is always 0.
◊
Register address. Indicates the address of the register to be accessed. In commands on
multiple registers, defines the Start Register from which to operate consecutively.
◊
Data. Formed by 2 bytes (single operations) or set of 2 bytes (multiple operations) that
contain the command information.
◊
CRC. 2 bytes are added to the end of the frame in order to detect errors in transmission or
reception. The Cyclic Redundant Code (CRC) check method is used for this.
The generator polynomial is: CRC-16 = x
Register
Zone address
address
1 byte 1 byte
+ x + x + 1.
16 15 2
Data CRC
1...2·N bytes 2 bytes
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