ModBus ASCII

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WebHMI supports various devices using the ModBus ASCII protocol

Version 1.5 supports 4 types of ModBus regisers :

Cxx - Coils

Flag registers

ModBus functions: read - 0x01, write - 0x05

Data type: Bit

Register range: 0 <= xx <= 65535

Examples: C0, C12, C65535

DIxx - Discrete Inputs

Digital input registers

ModBus function: read- 0x02

Data type: Bit

Registers range: 0 <= xx <= 65535

Examples: DI0, DI2, DI65535

HRxx - Holding Registers

Holding Registers.

ModBus functions : read - 0x03, write - 0x06

Data type: Word

Registers range: 0 <= xx <= 65535

Examples: HR0, HR1, HR2, HR65535

MHRxx - Multiple Holding Registers

These registers identical to HRxx. The difference is that for write operations Modbus #16 (Preset Multiple Register) function is used.

IRxx - Input Registers

Input registers type.

ModBus function: read - 0x04

Data type: Word

Register range: 0 <= xx <= 65535

Examples: IR0, IR1, IR2, IR65535

Note: By default, when reading double words, two queries will be used - one for each word. To explicitly set double-word reading by single query of multiple read type, you must enable grouping in the connection properties.