ABB ACS550/ACH550 drive (embedded fieldbus)

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 only confirmed at the hardware-verified rung.

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
control_word	0	U16	1
reference_1	1	I16	1
reference_2	2	I16	1
status_word	3	U16	1
speed	101	I16	1	rpm
freq_output	102	I16	0.1	Hz
current	103	I16	0.1	A
torque	104	I16	0.1	%
power	105	I16	0.1	kW
dc_bus_volt	106	I16	1	V
output_voltage	108	I16	1	V
kwh_counter	114	I16	1	kWh
di1_3_status	117	U16	1
ro1_3_status	121	U16	1
ro4_6_status	122	U16	1
last_fault	400	U16	1
previous_fault_1	401	U16	1
previous_fault_2	402	U16	1

link settings as documented (unverified): RTU; default 9600 8N2; unit ID 1; FC 01,02,03,04,05,06,08,15,16,23; Modbus RTU is supported on the RS485 embedded fieldbus interface. Default parity and stop bits setting is 8N2.

⚠ Connections should be made only while the drive is disconnected from the power source. — Starkest reads only; we never write a control register.

bench facts as documented (unverified)

terminals	X1:28...32
A/B polarity	Terminal 29 is B (Positive +), Terminal 30 is A (Negative -)
termination	120 Ohm resistors at both ends of the network, connected/disconnected via DIP switch J2
isolation	AGND (Terminal 31) is the logical ground
shield/ground	Connect shield to terminal 28 on one end, and terminal 32 on the other end. Do not connect incoming and outgoing shields to the same terminal.
wiring notes	Use Belden 9842 or equivalent dual twisted, shielded pair cable with wave impedance of 120 ohms.
protocol notes	Parameter writes through standard Modbus are always volatile. Use parameter 1607 (PARAM. SAVE) to save all altered values to permanent memory.
firmware register	45301
identification notes	Parameter 5301 (EFB PROTOCOL ID) contains the identification and program revision of the protocol in XXYY format.
doc revision	3AFE68320658 REV D
firmware applicability	ACH550-01/02/U1/U2 Drives

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

Reading non-consecutive registers or registers that do not correspond to valid parameters in a single block read request causes the drive to return an exception or corrupt responses rather than ignoring the invalid registers. [source]
Byte-swapping issues on PLCs (such as Modicon M580) can cause the drive to receive an invalid frequency reference, resulting in a DIR LOCK error 2004. [source]
confirmed: Baud rates [1200, 2400, 4800, 9600, 19200, 38400, 57600, 76800] and default baud 9600 — confirmed by ABB ACH550 User's Manual (Group 53 EFB Protocol)
confirmed: Default parity and stop bits setting is 8N2 (None parity, 2 stop bits) — confirmed by ABB ACH550 User's Manual (Parameter 5304 EFB PARITY default is 1, which corresponds to 8 NONE 2)
confirmed: Terminal 29 is B (Positive +), Terminal 30 is A (Negative -), and Terminal 31 is AGND — confirmed by ABB ACH550 RS485 Terminal Block X1 specifications
confirmed: Parameter writes through standard Modbus are volatile and require parameter 1607 (PARAM. SAVE) to save to permanent memory — confirmed by ABB ACS550/ACH550 User's Manual (Parameter 1607 description)
confirmed: Register map summary (e.g., speed @ 101 mapping to parameter 0102, freq_output @ 102 mapping to parameter 0103, etc.) — confirmed by ABB ACS550/ACH550 Modbus register mapping formulas (40000 + 100 * Group + Index)

generated by gemini:gemini-3.5-flash · harvested from https://library.e.abb.com/public/25ba8ab3f04e2266c12572e9004ffafe/EN_ACH550_EFB_D.pdf (ABB); manual-faithful — the document's claims, panel risk: LOW — panel concurs, no field disagreements; proved interop-verified on 2026-06-10 · recorded 2026-06-10

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.

Have a device that isn't here? Upload its register map — generation is free, and the connector earns its rung by being proven, not claimed.

Need it proven on your own device? Hardware verification — if it doesn't verify, you don't pay.

Building a platform? License the verified library — machine-readable maps, firmware matrix, API access.