Mitsubishi Electric A/C via Intesis ME-AC-MBS interface

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.

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.

point	address (0-based)	type	scale	unit
AC unit On/Off	0	U16	1
AC unit Mode	1	U16	1
AC unit Fan Speed	2	U16	1
AC unit Vane Position	3	U16	1
AC unit Temperature Setpoint	4	U16	1	ºC/ºF
AC unit Ambient Temperature	5	U16	1	ºC/ºF
Window Contact	6	U16	1
Device Disablement	7	U16	1
IR Remote Command Disablement	8	U16	1
AC unit Operation Time	9	U16	1	hours
AC unit Alarm Status	10	U16	1
Error Code	11	U16	1
AC Model	12	U16	1
Open Window switch-off timeout	13	U16	1	minutes
Modbus RTU baud-rate	14	U16	1
Device's Modbus slave address	15	U16	1
Software version	50	U16	1

link settings as documented (unverified): RTU; default 9600 8N1; unit ID 0; FC 03,04,06,16; Although function 16 is allowed, the interface does not allow write operations on more than 1 register with the same request, this means that length field should always be 1 when using this function for writes.

bench facts as documented (unverified)

terminals	plug-in terminal block of 2 poles
A/B polarity	A B
termination	on-board terminator resistor of 120Ω selectable via DIP-switch P5
connector	plug-in terminal block
isolation	1000 VDC isolation voltage, 1000 MΩ isolation resistance
wiring notes	Direct connection to the AC indoor unit via CN92 (Mr.Slim) or CN105 (other models).
broadcast	supported
protocol notes	Write operations on more than 1 register with the same request are not allowed.
firmware register	50
power	External power not required.
environment	Operating Temperature: -40 ... 85ºC, Operating Humidity: <95% RH, non-condensing
doc revision	rev.8
firmware applicability	v.1.13

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

confirmed: Baud rates [2400, 9600, 19200, 57600] with default 9600, 8N1 framing — confirmed by IntesisBox ME-AC-MBS-1 v.1.13 User Manual (rev.8)
confirmed: Function codes 3, 4, 6, 16 supported, but writes with function 16 are restricted to a length of 1 register — confirmed by IntesisBox ME-AC-MBS-1 v.1.13 User Manual (rev.8)
confirmed: Direct connection to the AC indoor unit via CN92 or CN105 — confirmed by IntesisBox ME-AC-MBS-1 v.1.13 User Manual (rev.8)
confirmed: Register map addresses (ac_unit_on_off @ 0, ac_unit_alarm_status @ 10, error_code @ 11, software_version @ 50) — confirmed by IntesisBox ME-AC-MBS-1 v.1.13 User Manual (rev.8)

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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