Issue
The Modbus Server / Client is unable to read the values from address of a 32 bit Modbus register in a Building Operation server
Product Line
EcoStruxure Building Operation
Environment
- Building Operation server
- Modbus
Cause
The original Modbus/JBUS protocol specifies the use of 16-bit integer registers for Analogue Inputs and Analogue Outputs. The number range able to be represented in 16-bits is:
Unsigned: 0 to 65353
Signed: -32768 to 32867
In order to represent larger numbers, it is common for 16-bit registers to be combined to represent 32-bit or 64-bit numbers. When a Modbus Client or Server reads a 32-bit Modbus value, it will be reading two consecutive 16-bit registers. An error will occur if two 32-bit Local Modbus registers are created in Building Operation using consecutive register addresses since only the starting modbus register address is used for the request.
Resolution
When configuring 32-bit Local Modbus registers in Building Operation, the next register address should not be used. Create the next Local Modbus register using the 3rd available Modbus register address.
