Yokogawa EJX/EJA-E pressure transmitter

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
pres	400	F32BE	1
sp	402	F32BE	1
et	404	F32BE	1
pres_usl	412	F32BE	1	kPa
pres_lsl	414	F32BE	1	kPa
pres_urv	416	F32BE	1	kPa
pres_lrv	418	F32BE	1	kPa
sp_usl	420	F32BE	1	MPa
sp_lsl	422	F32BE	1	MPa
sp_urv	424	F32BE	1	MPa
sp_lrv	426	F32BE	1	MPa
et_usl	428	F32BE	1	°C
et_lsl	430	F32BE	1	°C
et_urv	432	F32BE	1	°C
et_lrv	434	F32BE	1	°C
pres_damp	440	F32BE	1	s
sp_damp	446	F32BE	1	s
et_damp	452	F32BE	1	s
cap_temp	1128	F32BE	1
amp_temp	1130	F32BE	1

link settings as documented (unverified): RTU; default 9600 8N1; unit ID 1; FC 01,02,03,04,05,08,16,43; Turnaround delay time is configurable from 10 to 200 ms.

⚠ Do not connect power wiring to the MODBUS(RS-485) terminals. It may damage EJX Multivariable Transmitter. — Starkest reads only; we never write a control register.

bench facts as documented (unverified)

terminals	SUPPLY +, SUPPLY -, MODBUS A, MODBUS B, Ground terminal
A/B polarity	MODBUS A, MODBUS B
termination	Line termination can be selected by the hardware switch (Bus End / Not Bus End).
isolation	The EJX Multivariable Transmitter power supply is not electrically isolated from the RS-485 bus.
shield/ground	Grounding is always required for the proper operation of transmitters.
response timeout	3000 ms
inter-frame delay	100 ms
broadcast	supported
protocol notes	Host timeout period is recommended to be set larger than 3 s when transmitted data size is big. Host communication period between receiving response and sending request is recommended to be set larger than 100 ms under multi-drop connection.
model register	1005
serial register	1123
firmware register	1003
FC 43 device ID	supported
power	between 9 and 30 V dc with less than 2% ripple, and sufficient current capacity.
certifications	ATEX
doc revision	IM 01C25R05-01EN 1st Edition

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

confirmed: Baud rates [1200, 4800, 9600, 19200] with default 9600 — confirmed by User's Manual IM 01C25R05-01EN Table 5.1
confirmed: Default Unit ID 1 — confirmed by User's Manual IM 01C25R05-01EN Table 5.1
confirmed: Framing RTU — confirmed by User's Manual IM 01C25R05-01EN Table 5.1
confirmed: Function codes [1, 2, 3, 4, 5, 8, 16, 43] — confirmed by User's Manual IM 01C25R05-01EN Table 5.1
confirmed: Turnaround delay time is configurable from 10 to 200 ms — confirmed by User's Manual IM 01C25R05-01EN Section 5.1
confirmed: Do not connect power wiring to the MODBUS(RS-485) terminals. It may damage EJX Multivariable Transmitter — confirmed by User's Manual IM 01C25R05-01EN Section 2.1.2
confirmed: The EJX Multivariable Transmitter power supply is not electrically isolated from the RS-485 bus — confirmed by User's Manual IM 01C25R05-01EN Section 2.1.2
confirmed: Power supply between 9 and 30 V dc with less than 2% ripple — confirmed by User's Manual IM 01C25R05-01EN Section 2.1.2

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.
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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