Honeywell UDC2500/3200/3300 controller (Modbus comms option)

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
PV	0	I16	0.1
RV; Remote Set Point; SP2	1	I16	0.1
Working Set Point	2	I16	0.1
Output	3	I16	0.1
Input #1	4	I16	0.1
Input #2	5	I16	0.1
Gain #1 (Prop Band #1 if active)	6	I16	0.1
Direction	7	I16	0.1
Reset #1	8	I16	0.1
Rate #1	9	I16	0.1
Cycle Time #1	10	I16	0.1
PV Low Range	11	I16	0.1
PV High Range	12	I16	0.1
Alarm #1 SP #1	13	I16	0.1
Alarm #1 SP #2	14	I16	0.1
Alarm #1 Action	15	I16	0.1
Gain #2	16	I16	0.1
Deadband	17	I16	0.1
Reset #2	18	I16	0.1
Rate #2	19	I16	0.1
Cycle Time #2	20	I16	0.1
SP1; LSP #1	21	I16	0.1
LSP #2	22	I16	0.1
Alarm #2 SP #1	23	I16	0.1
Alarm #2 SP #2	24	I16	0.1
Alarm #2 Action	25	I16	0.1
SP Low Limit	26	I16	0.1
SP High Limit	27	I16	0.1
Working Set Point	28	I16	0.1
Output Low Limit	29	I16	0.1
Output High Limit	30	I16	0.1
Output Working Value	31	I16	0.1
PV Override Value	32	I16	0.1
SP Override Value	33	I16	0.1
Output Override Value	34	I16	0.1
Ratio	35	I16	0.1
Bias	36	I16	0.1
Deviation	37	I16	0.1
LSP #3	38	I16	0.1
Percent Carbon Monoxide - CO	39	I16	0.001
Decimal Point	40	I16	1
Alg1 Bias	41	I16	0.1
Alg2 Bias	42	I16	0.1
LSP #4	43	I16	0.1
Current Output #2	44	I16	0.1
Current Output #3	45	I16	0.1
Fuzzy Enable	56	U16	1
Shed Enable	57	U16	1
Auto/Manual State	58	U16	1
Set Point State	59	U16	1
Remote/Local Set Point State	60	U16	1
Tune Set State	61	U16	1
Loop Status	62	U16	1
Device Status	63	U16	1
PV	64	F32BE	1
RV; Remote Set Point; SP2	66	F32BE	1
Working Set Point	68	F32BE	1
Output	70	F32BE	1
Input #1	72	F32BE	1
Input #2	74	F32BE	1
Gain #1	76	F32BE	1
Direction	78	F32BE	1
Reset #1	80	F32BE	1
Rate #1	82	F32BE	1
Cycle Time #1	84	F32BE	1	Seconds
PV Low Range	86	F32BE	1
PV High Range	88	F32BE	1
Alarm #1 SP #1	90	F32BE	1
Alarm #1 SP #2	92	F32BE	1
Gain #2	96	F32BE	1
Deadband	98	F32BE	1
Reset #2	100	F32BE	1
Rate #2	102	F32BE	1
Cycle Time #2	104	F32BE	1	Seconds
LSP #1	106	F32BE	1
LSP #2	108	F32BE	1
Alarm #2 SP #1	110	F32BE	1
Alarm #2 SP #2	112	F32BE	1
SP Low Limit	116	F32BE	1
SP High Limit	118	F32BE	1
Working Set Point	120	F32BE	1
Output Low Limit	122	F32BE	1
Output High Limit	124	F32BE	1
Output Working Value	126	F32BE	1
PV Override Value	128	F32BE	1
SP Override Value	130	F32BE	1
Output Override Value	132	F32BE	1
Ratio	134	F32BE	1
Bias	136	F32BE	1
Deviation	138	F32BE	1
LSP #3	140	F32BE	1
LSP #4	142	F32BE	1
Gain #3	144	F32BE	1
Reset #3	146	F32BE	1
Rate #3	148	F32BE	1
Gain #4	150	F32BE	1
Reset #4	152	F32BE	1
Rate #4	154	F32BE	1
PV/SP Switch 3 to 4	156	F32BE	1
ALG1 Bias	158	F32BE	1
ALG2 Bias	160	F32BE	1
Aux Output	162	F32BE	1
Setpoint Ramp Time	164	F32BE	1
Setpoint Ramp Setpoint	166	F32BE	1
Input 1 Ratio	168	F32BE	1
Input 1 Bias	170	F32BE	1
Input 2 Ratio	172	F32BE	1
Input 2 Bias	174	F32BE	1
SP/PV Switch 1 to 2	176	F32BE	1
SP/PV Switch 2 to 3	178	F32BE	1
Input 3 Ratio	180	F32BE	1
Input 3 Bias	182	F32BE	1
Input 4 Ratio	184	F32BE	1
Input 4 Bias	186	F32BE	1
Input 5 Ratio	188	F32BE	1
Input 5 Bias	190	F32BE	1
Current 1 Output	192	F32BE	1
Current 3 Output	194	F32BE	1
Chart Speed	2048	F32BE	1	Hours/rev
# Chart Divisions	2050	F32BE	1
Chart Status	2052	F32BE	1
Pen 1	2054	F32BE	1
Pen 1 High Value	2056	F32BE	1
Pen 1 Low Value	2058	F32BE	1
Pen 2	2060	F32BE	1
Pen 2 High Value	2062	F32BE	1
Pen 2 Low Value	2064	F32BE	1
Pen 3	2066	F32BE	1
Pen 3 High Value	2068	F32BE	1
Pen 3 Low Value	2070	F32BE	1
Pen 4	2072	F32BE	1
Pen 4 High Value	2074	F32BE	1
Pen 4 Low Value	2076	F32BE	1
Analog Input #1	6144	F32BE	1
Analog Input #2	6146	F32BE	1
Analog Input #3	6148	F32BE	1
Analog Input #4	6150	F32BE	1
Analog Input #5	6152	F32BE	1
Analog Input #6	6154	F32BE	1
Analog Input #7	6156	F32BE	1
Analog Input #8	6158	F32BE	1
Analog Input #9	6160	F32BE	1
Analog Input #10	6162	F32BE	1
Analog Input #11	6164	F32BE	1
Analog Input #12	6166	F32BE	1
Analog Input #64	6270	F32BE	1
Communication Value #1	6272	F32BE	1
Communication Value #2	6274	F32BE	1
Communication Value #3	6276	F32BE	1
Communication Value #4	6278	F32BE	1
Communication Value #5	6280	F32BE	1
Communication Value #6	6282	F32BE	1
Communication Value #7	6284	F32BE	1
Communication Value #8	6286	F32BE	1
Communication Value #9	6288	F32BE	1
Communication Value #10	6290	F32BE	1
Communication Value #11	6292	F32BE	1
Communication Value #12	6294	F32BE	1
Communication Value #13	6296	F32BE	1
Communication Value #14	6298	F32BE	1
Communication Value #15	6300	F32BE	1
Communication Value #16	6302	F32BE	1
Communication Value #32	6334	F32BE	1
Math Value #1	6336	F32BE	1
Math Value #2	6338	F32BE	1
Math Value #3	6340	F32BE	1
Math Value #4	6342	F32BE	1
Math Value #5	6344	F32BE	1
Math Value #6	6346	F32BE	1
Math Value #7	6348	F32BE	1
Math Value #8	6350	F32BE	1
Math Value #9	6352	F32BE	1
Math Value #10	6354	F32BE	1
Math Value #11	6356	F32BE	1
Math Value #12	6358	F32BE	1
Math Value #13	6360	F32BE	1
Math Value #14	6362	F32BE	1
Math Value #15	6364	F32BE	1
Math Value #16	6366	F32BE	1
Math Value #17	6368	F32BE	1
Math Value #18	6370	F32BE	1
Math Value #19	6372	F32BE	1
Math Value #20	6374	F32BE	1
Math Value #21	6376	F32BE	1
Math Value #22	6378	F32BE	1
Math Value #23	6380	F32BE	1
Math Value #24	6382	F32BE	1
Math Value #25	6384	F32BE	1
Math Value #26	6386	F32BE	1
Math Value #27	6388	F32BE	1
Math Value #28	6390	F32BE	1
Math Value #29	6392	F32BE	1
Math Value #30	6394	F32BE	1
Math Value #31	6396	F32BE	1
Math Value #32	6398	F32BE	1
Math Value #256	6846	F32BE	1
Position	6864	F32BE	1
Input	6866	F32BE	1
Output	6868	F32BE	1
Remote Setpoint	6870	F32BE	1
Input Low Range	6872	F32BE	1
Input High Range	6874	F32BE	1
Relay #1 SP1	6876	F32BE	1
Relay #1 SP2	6878	F32BE	1
Relay #2 SP1	6880	F32BE	1
Relay #2 SP2	6882	F32BE	1
Relay #3 SP1	6884	F32BE	1
Relay #3 SP2	6886	F32BE	1
Relay #4 SP1	6888	F32BE	1
Relay #4 SP2	6890	F32BE	1
Deadband	6892	F32BE	1
Deviation	6894	F32BE	1
Totalizer Value #1	6912	F32BE	1
Totalizer Value #2	6914	F32BE	1
Totalizer Value #3	6916	F32BE	1
Totalizer Value #4	6918	F32BE	1
Totalizer Value #5	6920	F32BE	1
Totalizer Value #6	6922	F32BE	1
Totalizer Value #64	7038	F32BE	1
Hours	7136	U16	1
Minutes	7137	U16	1
Seconds	7138	U16	1
Month	7139	U16	1
Day	7140	U16	1
Year	7141	U16	1
Week Day	7142	U16	1
Alarm Status #1 - #16	7152	U16	1
Alarm Status #17 - #32	7153	U16	1
Alarm Status #33 - #48	7154	U16	1
Alarm Status #49 - #64	7155	U16	1
Alarm Status #65 - #80	7156	U16	1
Alarm Set Point Value #1	7168	F32BE	1
Alarm Set Point Value #2	7170	F32BE	1
Alarm Set Point Value #3	7172	F32BE	1
Alarm Set Point Value #4	7174	F32BE	1
Alarm Set Point Value #5	7176	F32BE	1
Alarm Set Point Value #6	7178	F32BE	1
Alarm Set Point Value #7	7180	F32BE	1
Alarm Set Point Value #8	7182	F32BE	1
Alarm Set Point Value #9	7184	F32BE	1
Alarm Set Point Value #10	7186	F32BE	1
Alarm Set Point Value #11	7188	F32BE	1
Alarm Set Point Value #12	7190	F32BE	1
Alarm Set Point Value #13	7192	F32BE	1
Alarm Set Point Value #14	7194	F32BE	1
Alarm Set Point Value #15	7196	F32BE	1
Alarm Set Point Value #16	7198	F32BE	1
Alarm Set Point Value #256	7678	F32BE	1
Set Point Programmer Output	7680	F32BE	1
Current Segment Number	7682	F32BE	1
Program Elapsed Time	7684	F32BE	1
Program Active Time	7686	F32BE	1
Segment Time Remaining	7688	F32BE	1
Start	7692	I16	1
Hold	7693	I16	1
Advance	7694	I16	1
Reset	7695	I16	1
Temperature	7744	F32BE	1	degrees F
Temperature Hi	7746	F32BE	1	degrees F
Temperature Lo	7748	F32BE	1	degrees F
Cycles	7750	F32BE	1	counts
Relay1 Cycles	7752	F32BE	1	counts
Relay2 Cycles	7754	F32BE	1	counts
Relay3 Cycles	7756	F32BE	1	counts
Relay4 Cycles	7758	F32BE	1	counts
Region0 Counts	7760	F32BE	1	counts
Region1 Counts	7762	F32BE	1	counts
Region2 Counts	7764	F32BE	1	counts
Region3 Counts	7766	F32BE	1	counts
Region4 Counts	7768	F32BE	1	counts
Region5 Counts	7770	F32BE	1	counts
Region6 Counts	7772	F32BE	1	counts
Region7 Counts	7774	F32BE	1	counts
Region8 Counts	7776	F32BE	1	counts
Region9 Counts	7778	F32BE	1	counts
Total Degrees Travelled	7780	F32BE	1	degrees
Accumulated Stall Time	7782	F32BE	1	minutes
Alarm Set Point Value #576	8318	F32BE	1
Tag Name	10192	U16	1
Date of Manufacture	10195	U16	1
Date Last Repaired	10198	U16	1
Date Last Calibrated	10201	U16	1
Actuator Serial Number	10204	U16	1
Actuator Model Number	10221	U16	1

link settings as documented (unverified): RTU; baud 300/600/1200/2400/4800/9600/19200/38400; FC 01,02,03,04,05,06,08,16,17,20,21

bench facts as documented (unverified)

wiring notes	The Modbus RTU allows the instrument to be a citizen on a data link shared with other devices that subscribe to the Modbus RTU RS-485 specification.
max registers/read	22
broadcast	not supported
protocol notes	Request delay time is 20 ms (or 3.5 characters for newer versions).
identification notes	Uses Function Code 17 (11h) to report Device ID.
FC 43 device ID	not supported
doc revision	Revision T

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

The standard UDC2500/3200 product manuals only document registers for Function Codes 20 and 21, which are proprietary and unsupported by most commercial Modbus masters. Users must refer to the separate Modbus RTU Serial Communications User Manual (51-52-25-66) to obtain the standard operational register map (FC03/FC04/FC06/FC16). [source]
The Ethernet IP address on the UDC2500/3200 Ethernet option card cannot be configured via the front keypad; it can only be configured using Honeywell's proprietary PIE (Process Instrument Explorer) software. The default IP address is 10.0.0.2. [source]
Writing setpoints or parameters continuously to the UDC controller via Modbus will cause premature EEPROM memory fatigue and eventual hardware failure. Setpoints should only be written on change or at the start of a segment. [source]
Writing to UDC2500 controllers using Function Code 6 can trigger Modbus Exception Code 3 (Illegal Data Value) due to High Limit FM approval constraints or incorrect register mapping. [source]
confirmed: comms defaults (baud rates up to 38400, 8-N-1 framing) — confirmed by Honeywell Modbus RTU Serial Communications User Manual (51-52-25-66, Rev T) and field integration notes on Control.com
confirmed: Function Code 17 (11h) used for Device ID — confirmed by Honeywell Modbus RTU Serial Communications User Manual
confirmed: pv_integer @ 0 (40001) and pv_float @ 64 (40065) — confirmed by Honeywell Modbus RTU Serial Communications User Manual and Control.com forum threads
confirmed: analog_input_1 @ 6144 (1800h) — confirmed by Honeywell Modbus RTU Serial Communications User Manual

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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