Addressing And Data Transmission In The Modbus Protocol; Unit Ids; Assignment Of The Sunspec Modbus Registers To Unit Ids; Modbus Register Number, Register Width And Data Block - SMA SUNNY TRIPOWER 60 Technical Information

SMA Solar Technology AG

3.4 Addressing and Data Transmission in the Modbus Protocol

3.4.1

Unit IDs

The Unit ID is a superordinate addressing type in the Modbus protocol. The assignment of the unit
IDs in the SunSpec Modbus profile for SUNNY TRIPOWER 60 devices is performed automatically
by the Inverter Manager. You can determine the unit IDs assigned by the Inverter Manager for the
connected SUNNY TRIPOWER 60 devices using the Local Commissioning and Service tool (LCS
tool).
The following table shows an overview of the unit IDs in the STP60 SunSpec Modbus profile:
Unit ID Explanation
125* This unit ID is reserved for the Inverter Manager.
126 to 167* The unit IDs from 126 to 167 are reserved for STP 60 devices.
*Deviation for firmware version < 1.45: Inverter Manager ID = 1; Inverter ID 2 to 43
3.4.2

Assignment of the SunSpec Modbus Registers to Unit IDs

The assignment of the parameters and measured values of the SMA devices to Modbus registers is
achieved using assignment tables and is also shown in this document (see Section 5 "STP60 Sun-
Spec Modbus Profile – Assignment Tables", page 15).
The assignment table "Gateway (Unit ID = 125)" contains the SunSpec Modbus registers that are
provided by the Inverter Manager.
The assignment table (Unit ID = 126 to 167) contains a summary of the SunSpec Modbus registers
supported by the STP60 as well as a brief description of the register data.
3.4.3

Modbus Register Number, Register Width and Data Block

A Modbus register is 16 bits wide. For wider data items, connected Modbus registers are used and
considered as data blocks. The number (CNT) of connected Modbus registers is indicated in the
SunSpec assignment tables. The register number of the first Modbus register in a data block is the
start address of the data block. The register numbering begins with 40001.
Offset of the Modbus register numbers (No.)
For the reading or writing of Modbus registers, use the register numbers reduced by the
offset 1 in each case. Example: Modbus register address = register number in the STP60
SunSpec Modbus profile – offset = 40001 – 1 = 40000.
Technical Information
Product Description
STP60-SunSpec_Modbus-TI-en-12 11