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  3. Neuron M503

Unipi Technology Neuron M503 Modbus register map

Unipi Neuron M503 PLC: 10 digital inputs, 4 digital outputs, 5 relay outputs, 5 analog inputs, 5 analog outputs (I/O in 2 sections)

  • Official
  • 196 registers
  • Modbus TCP
  • Revision 3 · 2026-11-10

Official: Written from the manufacturer's documentation, but not tested on a device yet. Check the map against the manufacturer's documentation before you write to a live device. Tested it? Report a test.

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Communication

Protocol
Modbus TCP
Unit ID
0
TCP port
502
Byte / word order
ABCD · bytes big-endian, words high first
Addresses
0-based

Connection values are defaults: the device may be configured differently.

Map

Registers
166 holding registers, 30 coils
Groups
16
Translation tables
3
Revision
3 · 2026-11-10
Added
()
File
maps/unipi/neuron-m503.mbmap.json · 31 KB · history
SHA-256
db3e264c31e834819438dd5d4c53b625a7b9802bcc7495d73787486beacab268
Manufacturer
www.unipi.technology

Sources and notes

  • Neuron M503 Modbus map · version 2.0
    Registers and Coils sections and description tables; listed on https://kb.unipi.technology/en:hw:04-extensions:downloads

Source: Neuron M503 Modbus map v2.0, Unipi technology

  • Addresses are those of the column 'Via Unit 0' (Modbus TCP unit id 0), where the sections of a Neuron controller share one address space: section 1 starts at 0, section 2 at 100, section 3 at 200, and so on. The document also gives per-section addresses for unit ids 1, 2 and 3, which are not used here.
  • Unipi Neuron uses Modbus TCP. By default the Modbus server listens only on the loopback interface; it can be opened to other interfaces by changing its systemd script (document, Brief protocol description). The TCP port and the unit id used here are not stated in the document: 502 is the Modbus default.
  • Registers marked Reserved or Obsolete in the document, and those named (Internal), are left out. Multi-register values are big-endian (most significant register first). The document types Real as a two-register floating point value, read here as float32; its text about half and single precision is ambiguous.
  • Coils (suffix (coil)) repeat digital inputs, outputs and some settings that also appear as bits of holding registers. Analog values are in the unit selected by the analog input or output configuration register; the document gives no unit for them. Storage - Vendor specific 1 to 3 depend on the microSD card (Swissbit pSLC: card series, unrecoverable CRC errors, wear level threshold %).
  • Some registers (the RS485 line configuration) have no address in the Via Unit 0 column; they are included for section 1 with the Via Unit 1 address, which is identical, and left out for the other sections. Registers whose name carries no I/O index are repeated in every section; the name then ends with (section N).
AreaAddressNameTypeAccessUnitScaleDescription
HR 0 bool bit 0 R
HR 0 bool bit 1 R
HR 0 bool bit 2 R
HR 0 bool bit 3 R
HR 1 bool bit 0 RW
HR 1 bool bit 1 RW
HR 1 bool bit 2 RW
HR 1 bool bit 3 RW
HR 5 uint16 R
HR 6 bool bit 0 RW
HR 6 bool bit 1 RW
HR 8 uint32 ABCD RW
HR 10 uint32 ABCD RW
HR 12 uint32 ABCD RW
HR 14 uint32 ABCD RW
HR 16 uint16 RW
HR 17 uint16 RW
HR 18 uint16 RW
HR 19 uint16 RW
HR 20 bool bit 0 RW
HR 20 bool bit 1 RW
HR 20 bool bit 2 RW
HR 20 bool bit 3 RW
HR 21 bool bit 0 RW
HR 21 bool bit 1 RW
HR 21 bool bit 2 RW
HR 21 bool bit 3 RW
HR 22 bool bit 0 RW
HR 22 bool bit 1 RW
HR 22 bool bit 2 RW
HR 22 bool bit 3 RW
HR 500 uint16 RW
HR 501 uint16 RW
HR 502 uint16 RW
HR 503 uint16 RW
HR 504 uint16 RW
HR 1000 uint16 R
HR 1001 uint16 bits 0–7 R
HR 1001 uint16 bits 8–15 R
HR 1002 uint16 bits 0–3 R
HR 1002 uint16 bits 4–7 R
HR 1002 uint16 bits 8–15 R
HR 1003 uint16 R
HR 1004 uint16 R
HR 1005 uint32 ABCD R
HR 1007 bool bit 0 RW
HR 1007 bool bit 1 RW
HR 1007 bool bit 2 RW
HR 1007 bool bit 3 RW
HR 1008 uint16 RW ms
HR 1009 uint16 R
HR 1010 uint16 RW µs ×100
HR 1011 uint16 RW µs ×100
HR 1012 uint16 RW µs ×100
HR 1013 uint16 RW µs ×100
HR 1014 bool bit 0 RW
HR 1014 bool bit 1 RW
HR 1014 bool bit 2 RW
HR 1014 bool bit 3 RW
HR 1015 bool bit 0 RW
HR 1015 bool bit 1 RW
HR 1015 bool bit 2 RW
HR 1015 bool bit 3 RW
HR 1016 bool bit 0 RW
HR 1016 bool bit 1 RW
HR 1016 bool bit 2 RW
HR 1016 bool bit 3 RW
HR 1017 uint16 RW
HR 1018 uint16 RW
HR 1019 uint16 RW
HR 1020 uint16 RW
HR 1021 uint16 RW
HR 1022 uint16 RW
HR 1023 uint16 RW
HR 1024 uint16 RW
HR 1025 uint16 RW
HR 1026 uint16 RW
HR 1027 uint16 RW
HR 1028 uint16 RW
HR 1029 uint16 RW
HR 1030 uint16 RW
HR 3000 float32 ABCD RW
HR 3002 float32 ABCD R
HR 4000 uint16 R
HR 4001 uint16 R
HR 4002 uint16 R
HR 4003 uint16 R
HR 4004 uint16 R
HR 4005 uint16 R
HR 100 bool bit 0 R
HR 100 bool bit 1 R
HR 100 bool bit 2 R
HR 100 bool bit 3 R
HR 100 bool bit 4 R
HR 100 bool bit 5 R
HR 101 bool bit 0 RW
HR 101 bool bit 1 RW
HR 101 bool bit 2 RW
HR 101 bool bit 3 RW
HR 101 bool bit 4 RW

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