Daikin VRV Modbus interface EKMBDXB

Register map(s) for this device, with a note of how far each has been checked. Addresses are 0-based, as on the wire. Scale and byte order are confirmed only at the hardware-verified rung.

structure-verified

Decode path is structurally sound (addresses, widths, finite values). Does NOT prove word order or scaling.

point	address (0-based)	type	scale	unit
unit_1_00_on_off_status	2000	U16	1
unit_1_00_operation_status	2001	U16	1
unit_1_00_room_temperature_set_point_read	2002	I16	0.1	°C
unit_1_00_room_temperature	2004	I16	0.1	°C
unit_1_00_leaving_water_set_point_heating_read	2800	I16	0.1	°C
unit_1_00_leaving_water_set_point_cooling_read	2801	I16	0.1	°C
unit_1_00_error_code	3600	U16	1
central_forced_off	1000	U16	1
unit_1_00_on_off_command	2000	U16	1
unit_1_00_operation_mode_setting	2001	U16	1
unit_1_00_room_temperature_set_point_write	2002	I16	0.1	°C
unit_1_00_leaving_water_set_point_heating_write	2400	I16	0.1	°C
unit_1_00_leaving_water_set_point_cooling_write	2401	I16	0.1	°C
unit_1_00_domestic_hot_water_storage_set_point_write	2402	I16	0.1	°C
unit_1_00_user_interface_lock	2800	U16	1	°C

link settings as documented (unverified): RTU; default 9600 8E1; FC 03,04,06,16; Silent internal time: 5ms at 9600bps, 2.5ms at 19200bps. Response time is Silent Interval Time + 20ms.

⚠ The number of control commands per indoor unit is limited to 7000 per year. — Starkest reads only; we never write a control register.

bench facts as documented (unverified)

terminals	X3M (RS-485), F1/F2 (DIII-net), X1M (Power supply)
A/B polarity	A+, B-
termination	SS2 On = 120 Ohm, SS3 On = 100 Ohm, SS1 not used. Factory default is 0 Ohm (SS2=Off & SS3=Off)
connector	Terminal strips
shield/ground	Protective earth
wiring notes	BMS RS485 (2 wire, max 500m), DIII net (F1F2) maximum 64 indoor units and maximum 10 outdoors
max registers/read	32
response timeout	25 ms
inter-frame delay	5 ms
broadcast	supported
protocol notes	The number of control commands per indoor unit is limited to 7000 per year.
power	220 – 240 VAC 50/60 Hz
environment	Temp range 0 till 60°C, Indoor installation, IP X0
doc revision	4P642495-1A– 2022.02

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

confirmed: comms.baud_rates: [9600, 19200], default_baud: 9600, framing: ['RTU'], parity: 'E', stop_bits: 1 — confirmed by Daikin Central Europe Modbus Interface DIII Design Guide (4P642495-1A– 2022.02)
confirmed: facts.control_warning: 'The number of control commands per indoor unit is limited to 7000 per year.' — confirmed by Daikin Central Europe Modbus Interface DIII Design Guide (4P642495-1A– 2022.02)
confirmed: facts.environment: 'Temp range 0 till 60°C, Indoor installation, IP X0' — confirmed by Daikin Central Europe Modbus Interface DIII Design Guide (4P642495-1A– 2022.02)
confirmed: facts.physical.terminals: 'X3M (RS-485), F1/F2 (DIII-net), X1M (Power supply)' — confirmed by Daikin Central Europe Modbus Interface DIII Design Guide (4P642495-1A– 2022.02)
confirmed: facts.power: '220 – 240 VAC 50/60 Hz' — confirmed by Daikin Central Europe Modbus Interface DIII Design Guide (4P642495-1A– 2022.02)
confirmed: quirks.max_read_registers: 32 — confirmed by Daikin Central Europe Modbus Interface DIII Design Guide (4P642495-1A– 2022.02)
confirmed: register_map: unit_1_00_on_off_status @ 2000, unit_1_00_on_off_command @ 2000 — confirmed by openHAB community integration and Daikin Central Europe Modbus Interface DIII Design Guide (4P642495-1A– 2022.02) where register 32001/42001 maps to 0-based address 2000

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.
coherence-checked — Round-trips through a real Modbus stack with no overlapping addresses and a word-order-sensitive codec — the map is internally coherent and wire-decodable. Does NOT prove byte-order or scaling match a real device: the emulator is seeded from the map's own types, so a uniformly wrong byte-order still round-trips. Only hardware-verified confirms byte-order/scale on the wire.
hardware-verified (software-key) x1 — Matched a real device with operator-attested readings as ground truth — the only rung that confirms word order + scaling on the wire.

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