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Multiprotocol I/O Modules BACnet User Manual


The MINI, MIX, and MAX series of multiprotocol I/O modules with RS485 and IP have been designed for building distributed control systems using MAC36, AAC20, or another controller. Each module is equipped with the most commonly used types of I/Os in building automation. Depending on the version, the modules are equipped with a mix of different types of I/O in one unit:

  • MINI series: 4 or 8 inputs and outputs;
  • MIX series: 18 or 38 inputs and outputs;
  • MAX series: 24 or 12 inputs or outputs.

All I/O modules have BTL, and MINI/MIX series–UL, certificates. The modules with RS485 and IP are factory-equipped with the two most popular open communication protocols: Modbus (RTU, ASCII, TCP/IP) and BACnet (MS/TP, IP), which are selected using DIP switches. Rotary switches are used to set the module address, which facilitates and accelerates the process of commissioning the system. Built-in mini USB allows for the initial configuration of the unit without external power supply.
Built-in Modbus TCP/IP to Modbus ASCII/RTU gateway enables to connect additional modules/devices that communicate via Modbus RS485.
Thanks to supporting open communication standards, I/O modules can be installed in both new and completed installations, as part of existing BMS. These versatile devices will fit any BMS perfectly.

The MIX38-IP (MIX series), 4TO-H-IP (MINI series), and 24I-IP (MAX series) modules

This user manual outlines all information specific to using I/O modules in the BACnet protocol.

Revision History




1.1010 Nov 2023
  • DHCP functionality added (MINI/MIX modules)
1.915 Feb 2023
  • New title of the user manual for all series of modules (MINI/MIX/MAX) - Multiprotocol I/O Modules User Manual;
  • MAX series of I/O modules added
  • DHCP functionality added (MAX modules)
1.825 May 2022Rebranded
1.713 Oct 2020
  • Improved functionality of the BBMD: new default IP address, registering to the BBMD server is disabled if the BBMD IP address is left default;

  • Introduced an option to disable web server access by changing the HTTP port to 0;

  • Corrected summary table for all modules;

  • Updated information about biasing resistors in MIX modules;

  • General improvements and bugfixes.

1.619 Feb 2020
  • New temperature sensors implemented in Celsius and Fahrenheit degrees

  • Improved filtering on UI

  • Device Name (Object Name) in BACnet is saved in EEPROM memory

  • Fixed one record in sensor 30k6A1 table –resistance 60713 to 80713 (5°C)

  • “Send I Am” message is not sent if BACnet is turned off

1.55 Oct 2018
  • Corrections of typing errors in the text

  • Added imperial unit of measure

  • MINI and MIX modules earned UL recognized component mark

1.47 Dec 2017
  • Firmware Version 6.0 released with BACnet certification

  • fixed out of service flags in AO, BO and TO

  • fixed overridden flags in AO, BO and TO

  • fixed bug with number of counters for Binary input object (now variable is 32 bit)

  • changed AO-1, BO-1, TO-1 HAND_STATUS Access to read-only

  • changed resistance table for 2.2K3A1 sensor

1.316 May 2017
  • Hardware Version info added on the main tab on the web page and in the Modbus register

  • new action in the Modbus register no 0 – enter the bootloader

  • RS485 biasing control added for MINI IP modules with hardware version >= 2.0

  • new Device Object properties added: Version type, Baud rate, User Baud rate, IP address, Subnet mask, Default Gateway, HTTP port, and UDP port

  • www page: RS485 Biasing Resistors activating option (appears only in MINI modules with hardware >= 2.0)

  • www page fixed: COV increment always in a format with one decimal place

  • module names on the web page the corrected (added -H for all modules with hand operation switches)

1.24 Jan 2017
  • New HVAC functions Heating and Cooling in 4U4O based on output thermostatic control with a setpoint and differential value setting;

  • New input mode added for 4I4O: Time Relay NC [ms], Time Relay NO and NC in seconds, Input Forwarding;

  • New input mode added for 4U4O: Ordinary IO, Monostable Relay, Bistable Relay, Time Relay NO and NC [ms], Time Relay NO and NC in seconds, Input Forwarding, Heating, Cooling with corresponding BACnet objects and Modbus registers;

  • Output for resetting to default after input mode change in 4U4O and 4I4O;

  • Improved BACnet COV Increment now can have values with the resolution of 0.1;

  • BACnet COV Increment access (read/write) through USB added;

  • Power Led added, flashing when the I/O watchdog is triggered;

  • I/O watchdog reset after read/write registers through USB modified;

  • Sensors added for the immediate detection of short circuit and disconnection, regardless of filter settings on universal inputs;

  • Fixed bug with Stop bits, it was always 1.

1.11 Feb 2016
  • Information about the capacitive load relay added to the technical specifications.

  • Information about load triac outputs added to the technical specifications.

  • Information about COV added.

  • New BACnet objects UP_TIME and WATCHDOG. 

  • Universal Inputs: COV support and new feature of flag OUT_OF_SERVICE added.

  • Universal Inputs: new objects added: UI_CONFIGRATION, UI_RESOLUTION, UI_FILTER and UI_DRY CONTACT.

  • Digital Inputs: COV support and new feature of flag OUT_OF_SERVICE added.

  • Digital Inputs: new objects added: BIA_COUNTER, and BI_COUNTER.

  • Analog Outputs: COV support and new feature of flags OUT_OF_SERVICE and STATUS_FLAG added.

  • Analog Outputs: new objects added: AO_CONFIGURATION, AO_HAND_STATUS, and AO_HAND_VALUE.

  • Digital Outputs: COV support and new feature of flag OUT_OF_SERVICE and STATUS_FLAG added.

  • Digital Outputs: new object added:HAND_STATUS. 

  • Description of the new MINI module 4x Triac Outputs added: 4TO-H and 4TO-H-IP. 

  • MINI - 4I40-H and 4I40-H-IP module built-in application: Change of logic in the Time relay mode. Now the timer counts from the falling edge (is used to do it from the rising edge).

  • MINI - 4I40-H and 4I40-H-IP Module built-in application: new objects added MODE_TIME, COMMAND, and BLOCKING.

  • Shortlist of BACnet objects added.

  • Tables with PT1000 and NI1000 updated with more accurate data, due to new FW measuring the temperature at these sensors with 0.1°C accuracy.


28 Aug 2015

First edition

Revision history

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