SDM01 Modbus RTU Map

Status: Stable | Applies to: SDM01 Combo ALL | Updated: 2026-04-01

1. Applied Product Models

#	Ordering Number	Description
1	SDM01-TWM-12TS	SCTA-3×120A/Φ16 Wi-Fi (Tuya LAN+) + RS485
2	SDM01-TWM-20TS	SCTA-3×200A/Φ20 Wi-Fi (Tuya LAN+) + RS485
3	SDM01-TWM-12	SCTA-3×120A/Φ16 Wi-Fi (Tuya) + RS485
4	SDM01-TWM-20	SCTA-3×200A/Φ20 Wi-Fi (Tuya) + RS485
5	SDM01-TZM-12	SCTA-3×120A/Φ16 Zigbee (Tuya) + RS485
6	SDM01-TZM-20	SCTA-3×200A/Φ20 Zigbee (Tuya) + RS485
7	SDM01-EWM-12	SDM01 SCTA-3×120A/Φ16 Wi-Fi (ESP32) + RS485
8	SDM01-EWM-20	SDM01 SCTA-3×200A/Φ20 Wi-Fi (ESP32) + RS485
9	SDM01-TZM-12-U01	SDM01 SCTA-3×120A/Φ16 Zigbee (Std. ZB3.0) + RS485
10	SDM01-TZM-20-U01	SDM01 SCTA-3×200A/Φ20 Zigbee (Std. ZB3.0) + RS485

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2. Physical Layer & Wiring Guide

💡 Default Communication Parameters: Baud Rate: 9600 bps | Data Bits: 8 | Parity: None | Stop Bits: 1 | Default Address: 247

• Cable Type: Twisted pair cable (Shielded highly recommended for industrial environments).

• Topology: Bus (Daisy-chain). Strictly avoid Star or T-branch wiring.

• Cable Specification: AWG 24-16.

• Maximum Distance: 800 - 1200m (at 9600 bps).

• Termination Resistor: 120Ω (Required at both physical endpoints of the bus).

• Bus Capacity: Max 32 nodes per segment (Up to 256 nodes if using 1/8 Unit Load drivers).

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3. Modbus Register Map

📌 General Notes for Integrators

• Function Codes Supported: 0x03 (Read Holding), 0x04 (Read Input), 0x06 (Write Single), 0x10 (Write Multiple).

• Endianness (Byte Order): All FLOAT32 data types follow Big-Endian (ABCD) byte order.

• Register Offset: All addresses listed below are 0-based (Protocol Addresses). If your PLC/Master requires 1-based addressing (e.g., 40001 format), please add 40001 to the DEC address.

3.1 Product Identification

Address (DEC)	Address (HEX)	Description	Func Code	R/W	Bytes	Data Type	Value / Range
100	0x0064	Meter Type	03, 04	R	20	UTF8 String	"iMeter_3PN" (or Custom)
110	0x006E	Manufacturer	03, 04	R	20	UTF8 String	"The Manufacturer" (or Custom)
120	0x0078	Product ID	03, 04	R	10	UTF8 String	"SDM01x" (or Custom)
125	0x007D	Serial Number	03, 04, 10	R/W	10	UTF8 String	"YYWWZZZZ" (Digits only)
130	0x0082	Hardware Version	03, 04	R	10	UTF8 String	Format: "xxx.xx.xx"
135	0x0087	Firmware Version	03, 04	R	10	UTF8 String	Format: "xxx.xx.xx"

3.2 Basic Metering Data

Note: All Float32 values occupy 2 Modbus Registers (4 Bytes).

Address (DEC)	Address (HEX)	Description	Func Code	R/W	Data Type	Range	Unit
1000	0x03E8	Voltage A-N	03, 04	R	FLOAT32	0 - 1000	V
1002	0x03EA	Voltage B-N	03, 04	R	FLOAT32	0 - 1000	V
1004	0x03EC	Voltage C-N	03, 04	R	FLOAT32	0 - 1000	V
1006	0x03EE	Current A	03, 04	R	FLOAT32	0 - 1000	A
1008	0x03F0	Current B	03, 04	R	FLOAT32	0 - 1000	A
1010	0x03F2	Current C	03, 04	R	FLOAT32	0 - 1000	A
1012	0x03F4	Active Power A	03, 04	R	FLOAT32	-1000 - 1000	kW
1014	0x03F6	Active Power B	03, 04	R	FLOAT32	-1000 - 1000	kW
1016	0x03F8	Active Power C	03, 04	R	FLOAT32	-1000 - 1000	kW
1018	0x03FA	Reactive Power A	03, 04	R	FLOAT32	-1000 - 1000	kVAR
1020	0x03FC	Reactive Power B	03, 04	R	FLOAT32	-1000 - 1000	kVAR
1022	0x03FE	Reactive Power C	03, 04	R	FLOAT32	-1000 - 1000	kVAR
1024	0x0400	Apparent Power A	03, 04	R	FLOAT32	-1000 - 1000	kVA
1026	0x0402	Apparent Power B	03, 04	R	FLOAT32	-1000 - 1000	kVA
1028	0x0404	Apparent Power C	03, 04	R	FLOAT32	-1000 - 1000	kVA
1030	0x0406	Power Factor A	03, 04	R	FLOAT32	-1.0 - 1.0	-
1032	0x0408	Power Factor B	03, 04	R	FLOAT32	-1.0 - 1.0	-
1034	0x040A	Power Factor C	03, 04	R	FLOAT32	-1.0 - 1.0	-
1036	0x040C	Average Voltage L-N	03, 04	R	FLOAT32	0 - 1000	V
1038	0x040E	Average Line Current	03, 04	R	FLOAT32	0 - 1000	A
1040	0x0410	Unbalanced Line Currents	03, 04	R	FLOAT32	-300 - 300	%
1042	0x0412	Total Line Currents	03, 04	R	FLOAT32	0 - 3000	A
1044	0x0414	Total Active Power	03, 04	R	FLOAT32	-3000 - 3000	kW
1046	0x0416	Total Reactive Power	03, 04	R	FLOAT32	-3000 - 3000	kVAR
1048	0x0418	Total Apparent Power	03, 04	R	FLOAT32	-3000 - 3000	kVA
1050	0x041A	Total Power Factor	03, 04	R	FLOAT32	-1.0 - 1.0	-
1052	0x041C	Frequency	03, 04	R	FLOAT32	0 - 1000	Hz
1054	0x041E	Total Import Active Energy	03, 04	R	FLOAT32	±1,999,999,999	kWh
1056	0x0420	Total Export Active Energy	03, 04	R	FLOAT32	±1,999,999,999	kWh
1058	0x0422	Total Import & Export Active Energy	03, 04	R	FLOAT32	±1,999,999,999	kWh
1060	0x0424	Phase A Import Active Energy	03, 04	R	FLOAT32	±1,999,999,999	kWh
1062	0x0426	Phase A Export Active Energy	03, 04	R	FLOAT32	±1,999,999,999	kWh
1064	0x0428	Phase A Import & Export Active Energy	03, 04	R	FLOAT32	±1,999,999,999	kWh
1066	0x042A	Phase B Import Active Energy	03, 04	R	FLOAT32	±1,999,999,999	kWh
1068	0x042C	Phase B Export Active Energy	03, 04	R	FLOAT32	±1,999,999,999	kWh
1070	0x042E	Phase B Import & Export Active Energy	03, 04	R	FLOAT32	±1,999,999,999	kWh
1072	0x0430	Phase C Import Active Energy	03, 04	R	FLOAT32	±1,999,999,999	kWh
1074	0x0432	Phase C Export Active Energy	03, 04	R	FLOAT32	±1,999,999,999	kWh
1076	0x0434	Phase C Import & Export Active Energy	03, 04	R	FLOAT32	±1,999,999,999	kWh

3.3 RS485 Communication Settings

Address (DEC)	Address (HEX)	Description	Func Code	R/W	Data Type	Value Mapping	Default
6000	0x1770	Modbus Address	03, 04, 06, 10	R/W	UINT16	1 - 246 (Valid Node IDs)	247
6001	0x1771	Baud Rate	03, 04, 06, 10	R/W	UINT16	0 = 9600 1 = 2400 2 = 4800 3 = 9600 4 = 19200 5 = 38400	0 (9600 bps)
6002	0x1772	Parity / Stop Bits	03, 04, 06, 10	R/W	UINT16	0 = N, 8, 1 1 = E, 8, 1 2 = O, 8, 1 3 = N, 8, 2	0 (N, 8, 1)

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4. Control & Broadcast Commands

4.1 Device Specific Commands (Unicast)

Send these commands to a specific device's Modbus address.

Address (DEC)	Address (HEX)	Description	Func Code	R/W	Data Type	Write Value
10000	0x2710	Trigger LED Blinking (Device Locating)	06	W	UINT16	0x5055 (20565)
10001	0x2711	Reset Energy Accumulators	06	W	UINT16	0x51AA (20906)

🔍 Feature: Device Locating via LED When multiple meters are installed in a dense electrical panel, send 0x5055 to a specific device's Slave ID. The target meter's LED will blink rapidly for 15 seconds, allowing field engineers to visually identify the physical device corresponding to that IP/Slave ID.

4.2 Broadcast Address Assignment

Send this command to Broadcast Address 0.

Address (DEC)	Address (HEX)	Description	Func Code	R/W	Data Type	Write Value
30000	0x7530	Assign Modbus Address (Button Triggered)	10	W	2× UINT16	0x55AA + [New Address]

🛠️ How to use Broadcast Address Assignment: This feature allows quick commissioning without needing to wire devices one by one.

1. The Host PLC sends a broadcast write command (Slave ID = 0) to register 30000.

2. The payload must be 2 words (4 bytes): 0x55AA followed by the [New Address] (e.g., 0x0005).

3. Action: Only the meter that currently has its physical reset button pressed will accept this command and update its address. All other meters on the bus will ignore it.

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5. Compatible Meter Emulation

To ensure seamless integration with existing Home Energy Management Systems (EMS) automation applications - such Dynamic Load Balancing and Export limiting, the SDM01 series features automatic register mapping emulation for the standard versions of industry-leading meters.

The compatibility depends on the specific SDM01 model series, as detailed in the table below:

SDM01 Model Series	Compatible Emulation (Standard Versions)
SDM01-TWM-* SDM01-TZM-*	• Eastron SDM630MCT • ABB B23
SDM01-EWM-* SDM01-TZM-*-U01	• Eastron SDM630MCT • ABB B23 • CHINT DTSU666

Scope of Emulation: This emulation covers all commonly used core electrical parameters. If your PLC, SCADA, or automation system already has a built-in driver or template for the meters above, you can connect the SDM01 and read data directly without modifying your Modbus polling profiles.

The seamlessly mapped parameters include:

• Voltage (U) & Current (I) (Per phase)

• Power (Per phase Active Power and Total Active Power)

• Energy (Per phase Forward Active Energy and the Total Value, Per phase Reserve Active Energy and the Total Value)

(Note: Emulation focuses on standard metering data. Manufacturer-specific diagnostic or hardware configuration registers are not included. Important: In solar export limiting applications, brands like Eastron and CHINT frequently supply customized models to specific inverter manufacturers. These custom versions may have modified register maps that are incompatible with the standard common registers. If you are unsure about the compatibility of your specific meter version, please contact the document maintainer for confirmation.)