Modbus Registers Tables

Table Format

• Address: a 16-bit register address in hexadecimal. The address is the data used in the Modbus frame.

• Register: a 16-bit register number in decimal (register = address + 1).

• RW: register read-write status

  • R: read-only access

  • RW: read access and write access using Modbus functions

• Unit: the unit the information is expressed in.

• Type: the encoding data type (refer to Data Types).

• Range: the permitted values for this register, usually a subset of what the format allows.

• Factory: value of the variable in a new device, and after a reset to factory setting command.

• Saved:

  • YES: the value is saved in case of power loss.

  • NO: the value is not saved in case of power loss.

• Bit: bit number for BITMAP description.

• Description: provides information about the register and restrictions that apply.

Data Types

Data Type: BITMAP

A BITMAP register is a 16-bit register that can be read:

• as a 16-bit unsigned integer, using the Read multiple register function (function code 0x03)

• as a collection of bits, using the Read bits functions (function code 0x01 or 0x02)

Notes

• The type column tells how many registers to read to get the variable. For instance INT16U requires reading one register, whereas INT32 requires reading 2 registers.

• Some variables must be read as a block of multiple registers. Reading the block partially results in an error.

• Reading from an undocumented register results in a Modbus exception. Refer to Modbus Exception Codes.

• Numerical values are given in decimal. When it is useful to have the corresponding value in hexadecimal, it is shown as a C language type constant: 0xdddd. For example, the decimal value 123 is represented in hexadecimal as: 0x007B.

• INT32U or INT32 variables are stored in big-endian format: the most significant register is transmitted first, the least significant second.

• Out of order and not applicable values depend on the data type.