Modbus Table Format and Data Types

Table Formats

Address

Register

No.

Unit

Type

Range

Default Value

Svd

Function Code

Applicable Devices

Description

Designation	Description
Address	16-bit register address in hexadecimal. The address is the data used in the Modbus frame.
Register	16-bit register number in decimal. Register = Address + 1
No	Number of 16-bit registers that need to be read/written to access the complete information
R/RW	Whether the register is read only (R/RW) or read-write (RW).
X	Scale factor: A scale of 1 means that the value of the register is the right one with the unit indicated. A scale of 10 means that the register contains the value multiplied by 10. The actual value is therefore the value of the register divided by 10. A scale of 0.1 means that the register contains the value multiplied by 0.1. The actual value is therefore the value of the register multiplied by 10.
Unit	Information unit of measurement: “–”: no unit corresponding to the value expressed. “h”: hours “D”: the unit depends on the connected device.
Type	Coding data type (see Data type table below).
Range	Range of permitted values for the variable, usually a subset of what the format allows. For BITMAP type data, the content of this domain is “–”.
Default Value	Default value for the variable
Svd	Value saved when the power supply to the PowerTag Link gateway is switched off: “Y”: the value of the register is saved. “N”: the value is lost. NOTE: On start-up or reset, the available values are retrieved.
Function code	Code of functions that can be used in the register.
Applicable Devices	Code indicating the types of devices for which the register is available.
Description	Information about the register and the restrictions that apply.

Data Types

Name	Description	Range
INT16	16-bit signed integer (1 word)	-32768...+32767
UINT16	16-bit unsigned integer (1 word)	0...65535
INT32	32-bit signed integer (2 words)	-2 147 483 648...+2 147 483 647
UINT32	32-bit unsigned integer (2 words)	0...4 294 967 295
INT64	64-bit signed integer (4 words)	-9 223 372 036 854 775 808...9 223 372 036 854 775 807
UINT64	64-bit unsigned integer (4 words)	0 to 18 446 744 073 709 600 000
Float32	32-bit value (2 words)	-3.4028E+38... +3.4028E+38
ASCII	8-bit alphanumeric character	Table of ASCII Characters
BITMAP	16-bit field (1 word)	–
DATETIME	Refer to DATETIME	–

NOTE:

Float32 type data: Single precision float with sign bit, 8 bits exponent, 23 bits mantissa (positive and negative normalized real)

For ASCII type data, the order of transmission of characters in words (16-bit registers) is as follows:

Character n as least significant
Character n + 1 as most significant

All registers (16-bit or 2 bytes) are transmitted with Big Endian coding:

The most significant byte is transmitted first.
The least significant byte is transmitted second.

32-bit variables saved on two 16-bit words (e.g. consumption meters) are in Big Endian format:

The most significant word is transmitted first, then the least significant.

64-bit variables saved on four 16-bit words (e.g. dates) are in Big Endian format:

The most significant word is transmitted first, and so on.

DATETIME

DATETIME is a data type used to code date and time defined by the IEC 60870-5 standard.

Register	Type	Bit	Range	Description
1	INT16U	0–6	0x00–0x7F	Year: 0x00 (00) to 0x7F (127) correspond to years 2000 to 2127 For example, 0x0D (13) corresponds to year 2013.
1	INT16U	7–15	–	Reserved
2	INT16U	0–4	0x01–0x1F	Day
		5–7	–	Reserved
		8–11	0x00–0x0C	Month
		12–15	–	Reserved
3	INT16U	0–5	0x00–0x3B	Minutes
		6–7	–	Reserved
		8–12	0x00–0x17	Hours
		13–15	–	Reserved
4	INT16U	0–15	0x0000–0xEA5F	Milliseconds

Direct Bit Addressing

Addressing is permitted for BITMAP type zones with functions 1, 2, 5, and 15.

The address of the first bit is constructed as follows: (register address x 16) + bit number.

This addressing mode is specific to Schneider Electric.

Example: For functions 1, 2, 5, and 15, bit 3 of register 0x0078 should be addressed; the bit address is therefore 0x0783.

NOTE: The register whose bit needs to be addressed should have an address ≤ 0x0FFF.

Example of Modbus Frames

Request

Definition	Number of Bytes	Value	Comment
Server number	1 byte	0x05	PowerTag Link Modbus Address
Function code	1 byte	0x03	Reads n output or internal words
Address	2 bytes	0x36E2	Address of a consumption meter whose address is 14050 in decimal notation.
Number of words	2 bytes	0x002C	Reads 44 16-bit registers.
CRC	2 bytes	xxxx	Value of CRC16.

Response

Definition	Number of Bytes	Value	Comment
Server number	1 byte	0x05	PowerTag Link Modbus Address
Function code	1 byte	0x03	Reads n output or internal words
Number of Bytes	2 bytes	0x0058	Number of bytes read
Value of words read	88 bytes	–	Reads 44 16-bit registers
CRC	2 bytes	xxxx	Value of CRC16.

Modbus Register

The address of register number n is n-1. The tables detailed in the following parts of this document provides both register numbers (in decimal format) and corresponding addresses (in hexadecimal format). For example, the address of register number 3000 is 0x0BB7 (2999).

NOTE: To know the description of the registers of each associated device (how to use them), print the PDF report of Modbus registers using EcoStruxure Power Commission software (refer to EcoStruxure Power Commission Online Help). This report gives a dynamic knowledge of all the registers potentially to be integrated into the supervision systems including a description of each register.