Multiprotocol I/O Modules Modbus User Manual

Introduction

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.

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

Revision History

Date	Rev.	Description
23 Jul 2025	1.12	New description for sending Modbus RTU errors New intermessage delay functionality Updated RS485 Port section
15 Mar 2024	1.11	Updated UI temperature input type information
10 Nov 2023	1.10	DHCP functionality added (MINI/MIX modules) Modbus TCP free sockets counter functionality added (MINI/MIX modules)
15 Feb 2023	1.9	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) Modbus TCP free sockets counter functionality added (MAX modules)
25 May 2022	1.8	Rebranded
13 Oct 2020	1.7	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.
19 Feb 2020	1.6	New temperature sensors implemented in Celsius and Fahrenheit degrees New Modbus function 0x17 Read/Write Multiple registers New Modbus function 0x2B to read the VENDOR_NAME,MODEL_NAME, FW_VERSION, HOMEPAGE Supporting Modbus address 0xFF for communication with the gateway (IP module) Improved filtering on UI Fixed one record in sensor 30k6A1 table –resistance 60713 to 80713 (5°C)
5 Oct 2018	1.5	Corrections of typing errors in the text Added imperial unit of measure
7 Dec 2017	1.4	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
16 May 2017	1.3	Hardware Version information on the main tab on the web page and in the Modbus register added new action in Modbus register no 0 – enter the bootloader RS485 biasing control added for MINI IP modules with hardware version >= 2.0 www page: RS485 Biasing Resistors activating option (appears only in MINI modules with hardware >= 2.0) modules names on web page corrected (added -H for all modules with hand operation switches)
3 Jan 2017	1.2	New HVAC functions: Heating and Cooling in 4U4O, based on output thermostatic control with a setpoint and differential value setting; New input mode for 4I4O added: 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 added 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 detecting short circuit and disconnection, regardless of filter settings on universal inputs; Fixed bug with Stop bits, it was always 1.
1 Feb 2016	1.1	Information about the capacitive load relay added to the technical specifications. Information about load Triac Outputs added to the technical specifications. Description of the new MINI module 4x Triac Outputs: 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 (it used to start counting from the rising edge). New gateway functionality blocking Send Modbus Error. Tables with PT1000 and NI1000 updated with more accurate data with new FW measuring resistance at these sensors with the accuracy of 0.1 Ω.
28 Aug 2015	1.0	First edition

Revision history