Legrand EMDX3 multifunction meter (4 120 45)

Register map(s) for this device, each at the trust rung it earned. Addresses are 0-based as on the wire. Word order and scaling are confirmed at the hardware-verified rung and at no rung below it.

interop-verified

Read + decoded cleanly over a real network vs an independent third-party Modbus test server (transport and framing; reads are remapped into the server's register window, so the map's own addresses are NOT exercised). Does NOT prove word order/scaling against the actual device.

point	address (0-based)	type	scale	unit
phase_1_voltage	4096	U32BE	0.001	mV
phase_2_voltage	4098	U32BE	0.001	mV
phase_3_voltage	4100	U32BE	0.001	mV
phase_1_current	4102	U32BE	0.001	mA
phase_2_current	4104	U32BE	0.001	mA
phase_3_current	4106	U32BE	0.001	mA
neutral_current	4108	U32BE	0.001	mA
chained_voltage_l1_l2	4110	U32BE	0.001	mV
chained_voltage_l2_l3	4112	U32BE	0.001	mV
chained_voltage_l3_l1	4114	U32BE	0.001	mV
three_phase_active_power	4116	U32BE	1	W
three_phase_reactive_power	4118	U32BE	1	var
three_phase_apparent_power	4120	U32BE	1	VA
three_phase_positive_active_energy	4124	U32BE	1	Wh
three_phase_positive_reactive_energy	4126	U32BE	1	varh
three_phase_negative_active_energy	4128	U32BE	1	Wh
three_phase_negative_reactive_energy	4130	U32BE	1	varh
three_phase_power_factor	4132	I16	0.01
frequency	4134	U16	0.1	Hz
phase_1_thd_v1	4170	U16	0.1	%
phase_2_thd_v2	4171	U16	0.1	%
phase_3_thd_v3	4172	U16	0.1	%
phase_1_thd_i1	4173	U16	0.1	%
phase_2_thd_i2	4174	U16	0.1	%
phase_3_thd_i3	4175	U16	0.1	%

link settings as documented (unverified): RTU; FC 03,16

bench facts as documented (unverified)

terminals	two-wire configuration
connector	standard EIA/TIA 485 (RS-485)
response timeout	300 ms
inter-frame delay	20 ms
model register	768

field reports — community-sourced, unverified (checked 2026-06-11)

The official Legrand Modbus Table document lists the measurement registers under the section 'INPUT REGISTERS - Words (R)'. However, attempting to read these registers using Modbus Function Code 04 (Read Input Registers) results in an 'Illegal Function' error. The device actually requires Function Code 03 (Read Holding Registers) to read these values, as specified in the 'Read Function Code' column of the table. [source]
confirmed: comms framing RTU, function codes 3 and 16, and 1 stop bit — confirmed by Legrand EMDX3 Cat.No 4 120 45 Modbus Table document
confirmed: model register 768 — confirmed by Legrand EMDX3 Cat.No 4 120 45 Modbus Table document
confirmed: physical connector standard EIA/TIA 485 (RS-485) and two-wire configuration — confirmed by Legrand EMDX3 Cat.No 4 120 45 Modbus Table document
confirmed: inter-frame delay of 20ms and response timeout of 300ms — confirmed by Legrand EMDX3 Cat.No 4 120 45 Modbus Table document
confirmed: register map addresses (phase_1_voltage @ 4096, phase_1_current @ 4102, three_phase_active_power @ 4116, three_phase_positive_active_energy @ 4124, frequency @ 4134, phase_1_thd_v1 @ 4170) — confirmed by Legrand EMDX3 Cat.No 4 120 45 Modbus Table document

The trust ladder

Each rung states what it proved and what it did not. Gray until proven; green is earned by hardware only.

generated — A prompt produced it. Unproven — anyone can regenerate this.
structure-verified — Decode path is structurally sound (addresses, widths, finite values). Does NOT prove word order or scaling.
interop-verified — Read + decoded cleanly over a real network vs an independent third-party Modbus test server (transport and framing; reads are remapped into the server's register window, so the map's own addresses are NOT exercised). Does NOT prove word order/scaling against the actual device.
simulator-verified — Decoded correctly against a protocol emulator seeded with known-true values — catches word-order/scaling errors vs the emulator, not the physical device.
hardware-verified x1 — Matched a real device with operator-attested readings as ground truth — the only rung that confirms word order + scaling on the wire.

If your device isn't here, upload its register map. Generation is free, and the connector keeps the rung it earns under testing.

To prove a connector against your own device, order hardware verification. If it doesn't verify, you don't pay.

Platform builders can license the verified library: machine-readable maps, the firmware matrix, API access.