ABB TU844 3BSE021445R1 I/O module base

Overview

The TU844 (article number 3BSE021445R1) is a redundant Module Termination Unit (MTU) developed 

by ABB for the ABB Ability™ System 800xA® platform. As a passive termination component, it 

enables secure connection between field wiring and compatible S800 I/O modules, while supporting 

redundant ModuleBus distribution, I/O module addressing, and process power distribution. It is 

engineered for high-reliability industrial automation environments, with a focus on flexible signal 

routing and safety compliance.

Core Functionality

●Field Signal & Power Termination: Supports up to 8 I/O channels (2 terminals per channel) and 2+2 

process voltage connections (4 process power terminals + 4 process power 0 V terminals), enabling 2-

wire field device connections and integrated process power distribution.

●Redundant ModuleBus Distribution: Distributes two independent ModuleBuses to the paired I/O 

modules and cascades them to the next TU844 MTU, ensuring redundant communication for high-

availability systems.

●I/O Module Addressing: Generates correct addresses for connected I/O modules by shifting 

outgoing position signals to the subsequent MTU, facilitating sequential module identification in the 

system.

●Mechanical Keying: Features four mechanical keys (two per I/O module, 6 positions each) for 36 

possible configurations. This mechanical safeguard prevents insertion of incompatible I/O modules 

without affecting functional performance.

●Signal Configuration: Uses TY801 shunt sticks for individual channel configuration, allowing 

selection between voltage and current input types for field signals.

General Specifications