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  2. Unipi Technology
  3. Axon M505

Unipi Technology Axon M505 Modbus register map

Unipi Axon M505 PLC: 10 digital inputs, 4 digital outputs, 5 relay outputs, 5 analog inputs, 5 analog outputs, 1 RS485 line, 1-Wire bus (I/O in 2 groups)

  • Official
  • 217 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
160 holding registers, 57 coils
Groups
15
Translation tables
3
Revision
3 · 2026-11-10
Added
()
File
maps/unipi/axon-m505.mbmap.json · 44 KB · history
SHA-256
1eeaf3ae1e6ba75683a25b239280f77ef25c2edbf7b4e84c7a8b448ce4435d78
Manufacturer
www.unipi.technology

Sources and notes

Source: unipi-axon-m505-modbus-registers.xlsx, Unipi knowledge base page https://kb.unipi.technology/en:hw:04-extensions:downloads

  • Addresses are those of the column 'Via Unit 0' (Modbus TCP unit id 0), where the groups of an Axon controller share one address space: group 1 starts at 0, group 2 at 100, group 3 at 200, and so on. The spreadsheet also gives per-group addresses for unit ids 1, 2 and 3, which are not used here.
  • Unipi Axon and Neuron use 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 (Description sheet). The TCP port and the unit id used here are not stated in the spreadsheet: 502 is the Modbus default.
  • Registers marked Reserved or Obsolete in the spreadsheet, and those named (Internal), are left out. Multi-register values are big-endian (most significant register first). The spreadsheet types Real as a two-register floating point value, read here as float32; its Description sheet 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 spreadsheet gives no unit for them.
  • Some registers (the RS485 line configuration) have no address in the Via Unit 0 column; they are included for group 1 with the Via Unit 1 address, which is identical, and left out for the other groups.
  • Registers whose name carries no I/O index are repeated in every group of the controller; the name then ends with (group 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 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
HR 102 uint16 RW
HR 103 uint16 RW
HR 104 uint16 RW
HR 105 uint16 RW
HR 106 float32 ABCD R
HR 108 float32 ABCD R

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