MBMap Registry
  1. Devices
  2. Eastron
  3. SDM120CT

Eastron SDM120CT Modbus register map

Also covers SDM120CTM, SDM120CT-M

Single-phase DIN rail energy meter for an external current transformer (1 A or 5 A secondary)

  • Official
  • 35 registers
  • Modbus RTU
  • Revision 2 · 2026-10-17
  • Identity: serial number

Official: Written from the manufacturer's documentation, but not tested on a device yet. Check the map against the manufacturer's documentation before you write to a live device. Tested it? Report a test.

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Communication

Protocol
Modbus RTU
Unit ID
1
Serial
2400 8N1 · 2400 baud, 8 data bits, none parity, 1 stop bit
Byte / word order
ABCD · bytes big-endian, words high first
Addresses
0-based

Connection values are defaults: the device may be configured differently.

Map

Registers
14 holding registers, 21 input registers
Groups
6
Revision
2 · 2026-10-17
Added
()
File
maps/eastron/sdm120ct.mbmap.json · 8 KB · history
SHA-256
e61973b9b69eb93ad393bf7a0a276ff6b103ccde8847a7dbb9ab8a3c514772e6
Manufacturer
eastroneurope.com

Device identity

What a tool can read to check that this map fits the connected device (SPEC.md section 4.7). Registers with a role are read like any other register.

Registers
RoleRegisterAddressTypeValues
Serial number Serial number holding 64512 uint32 ABCD

Sources and notes

Source: Eastron, "Eastron SDM120CTM Smart Meter Modbus Protocol Implementation", V1.3

  • Measurements are float32 input registers (FC04); settings are float32 holding registers (FC03 read, FC10 write). The meter also answers FC08.
  • Requests must start at an even address and cover an even number of registers, so a single float32 is read or written as two registers. Only one float can be written per request.
  • The settings at F900h-F920h are 16-bit values in the protocol; read them together with the next register if the meter rejects a one-register read.
AreaAddressNameTypeAccessUnitScaleDescription
IR 0 float32 ABCD R V
IR 6 float32 ABCD R A
IR 12 float32 ABCD R W
IR 18 float32 ABCD R VA
IR 24 float32 ABCD R var
IR 30 float32 ABCD R
IR 70 float32 ABCD R Hz
IR 72 float32 ABCD R kWh
IR 74 float32 ABCD R kWh
IR 76 float32 ABCD R kvarh
IR 78 float32 ABCD R kvarh
IR 84 float32 ABCD R W
IR 86 float32 ABCD R W
IR 88 float32 ABCD R W
IR 90 float32 ABCD R W
IR 92 float32 ABCD R W
IR 94 float32 ABCD R W
IR 258 float32 ABCD R A
IR 264 float32 ABCD R A
IR 342 float32 ABCD R kWh
IR 344 float32 ABCD R kvarh
HR 0 float32 ABCD R min Minutes into the first demand calculation; demand values are valid once it reaches the demand period
HR 2 float32 ABCD RW min Default 60; 0 turns demand off
HR 12 float32 ABCD RW ms 60, 100 or 200 ms, default 100
HR 18 float32 ABCD RW Default 0. Takes effect after a restart
HR 20 float32 ABCD RW Modbus address, default 1
HR 28 float32 ABCD RW Default 0 (2400)
HR 50 float32 ABCD RW A Default 5
HR 52 float32 ABCD RW A 1 or 5, default 5
HR 86 float32 ABCD RW Default 4
HR 61456 uint32 ABCD W The protocol writes 00 00 here; requests must cover an even number of registers, so this sends two zero registers with FC10
HR 63744 uint16 RW s BCD, 0 to 30 s; 0 (default) = no automatic scrolling
HR 63760 uint16 RW Default 1
HR 63776 uint16 RW Default 2
HR 64512 uint32 ABCD R

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