Carlo Gavazzi EM330/EM340 energy meter

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
v_l1_n	0	U32LE	0.1	V
v_l2_n	2	U32LE	0.1	V
v_l3_n	4	U32LE	0.1	V
v_l1_l2	6	U32LE	0.1	V
v_l2_l3	8	U32LE	0.1	V
v_l3_l1	10	U32LE	0.1	V
a_l1	12	U32LE	0.001	A
a_l2	14	U32LE	0.001	A
a_l3	16	U32LE	0.001	A
w_l1	18	U32LE	0.1	W
w_l2	20	U32LE	0.1	W
w_l3	22	U32LE	0.1	W
va_l1	24	U32LE	0.1	VA
va_l2	26	U32LE	0.1	VA
va_l3	28	U32LE	0.1	VA
var_l1	30	U32LE	0.1	var
var_l2	32	U32LE	0.1	var
var_l3	34	U32LE	0.1	var
v_l_n_sys	36	U32LE	0.1	V
v_l_l_sys	38	U32LE	0.1	V
w_sys	40	U32LE	0.1	W
va_sys	42	U32LE	0.1	VA
var_sys	44	U32LE	0.1	var
pf_l1	46	I16	0.001
pf_l2	47	I16	0.001
pf_l3	48	I16	0.001
pf_sys	49	I16	0.001
hz	51	I16	0.1	Hz
kwh_pos_tot	52	U32LE	0.1	kWh
kvarh_pos_tot	54	U32LE	0.1	kvarh
kw_dmd	56	U32LE	0.1	W
kw_dmd_peak	58	U32LE	0.1	W
kwh_pos_partial	60	U32LE	0.1	kWh
kvarh_pos_partial	62	U32LE	0.1	kvarh
kwh_pos_l1	64	U32LE	0.1	kWh
kwh_pos_l2	66	U32LE	0.1	kWh
kwh_pos_l3	68	U32LE	0.1	kWh
kwh_neg_tot	78	U32LE	0.1	kWh
kvarh_neg_tot	80	U32LE	0.1	kvarh
thd_a_l1	130	U32LE	0.01	%
thd_a_l2	132	U32LE	0.01	%
thd_a_l3	134	U32LE	0.01	%
thd_v_l_n_sys	136	U32LE	0.01	%
thd_v_l1_n	138	U32LE	0.01	%
thd_v_l2_n	140	U32LE	0.01	%
thd_v_l3_n	142	U32LE	0.01	%
a_n	152	U32LE	0.001	A

link settings as documented (unverified): RTU; default 9600 8N1; unit ID 1; FC 03,04,06,08; Functions 03h and 04h have exactly the same effect and can be used indifferently. Maximum 50 registers can be read with a single request.

bench facts as documented (unverified)

terminals	A-, T
termination	120 ohm 1/2W 5% resistor between line B and A
shield/ground	Connect shield to GND on master side only
wiring notes	Suggested to use AWG24 balanced pair cable and add a third wire for GND connection.
max registers/read	50
response timeout	500 ms
inter-frame delay	40 ms
broadcast	supported
sentinel values	7FFFFFFFh (or EEE on display) for overflow
protocol notes	T null: Max interruption time during the request frame is 2.5 char
model register	11
serial register	20480
firmware register	770
identification notes	Model register is Carlo Gavazzi Controls identification code. Serial register is Letter 1 to Letter 7 starting at 5000h.
certifications	MID certification (PFA and PFB)
doc revision	Version 2 Revision 17 (July 05, 2021)

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

Word order for 32-bit registers (INT32, UINT32) is LSW-first (Little Endian word swap), which requires word swapping in master configurations to avoid garbled or extremely large values. [source]
RS-485 polarity labeling uses A- for Data- and B+ for Data+, which is opposite to some standard Modbus master labeling (where A is D+ and B is D-), frequently causing communication failures due to swapped wiring. [source]
confirmed: comms defaults: baud rate 9600, parity None, stop bits 1, unit ID 1, RTU framing — confirmed by EM300 Series Modbus manual and multiple integration guides (e.g., TapHome, evcc, Loxone)
confirmed: Functions 03h and 04h have exactly the same effect and can be used indifferently — confirmed by EM300 Series Modbus manual Section 1.2
confirmed: Maximum 50 registers can be read with a single request — confirmed by EM300 Series Modbus manual Section 1.2.1 and 1.2.2
confirmed: Suggested to use AWG24 balanced pair cable and add a third wire for GND connection — confirmed by EM300 Series Modbus manual Section 1.3.1
confirmed: Connect shield to GND on master side only — confirmed by EM300 Series Modbus manual Section 1.3.1
confirmed: Termination: 120 ohm 1/2W 5% resistor between line B and A, and connect terminal A- with T in the last instrument — confirmed by EM300 Series Modbus manual Section 1.3.1
confirmed: Broadcast supported only with function code 06h using address 00h — confirmed by EM300 Series Modbus manual Section 1.2.5
confirmed: Response timeout (T response) is 500 ms, inter-frame delay (T delay) is 40 ms, and T null (max interruption time) is 2.5 char — confirmed by EM300 Series Modbus manual Section 1.3.2

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.