AS-i Standard

AS-Interface represents an open and manufacturer-independent bus system. Actuators and sensors are connected to the control via an unshielded 2-wire line – with simultaneous transmission of data and energy.

The master, a power supply unit as well as various standard and safe stations (slaves) form the basis of every AS-i system. The master ensures data exchange with the slaves by means of cyclic polling. The AS-i power supply units supply the network's slaves and sensors with energy.

AS-Interface networks can be very comfortably directly connected to the SIMATIC control. For this purpose, so-called CPs or CMs are available. Integration is just as easy as with other expansion modules of SIMATIC controls by Siemens. Besides direct integration, AS-Interface can also be employed in a distributed manner via AS-i links as feeder for superior bus systems.


Key data per AS-i network

Number of slaves

Up to 62

Number of I/Os

Up to 496 inputs and 496 outputs


Any, combinable,  no termination resistors


Unshielded two-wire line for data and energy

Line length

100 m as a standard, extendable to 600 m with Repeater and Extension Plug 

Cycle time

5 ms (typical)

Data transfer

Digital and analog (16 bit)

Siemens as full-range solution provider

As the largest system supplier in the field of AS-Interface, Siemens offers a comprehensive product range of AS-i slaves. The portfolio ranges from simple and safe I/O modules for the field and the control cabinet to pushbuttons and signaling columns as well as position switches with AS-i connection right down to powerful motor starters and frequency converters, software tools (TIA Portal) and services.

Siemens = full-range AS-i portfolio

  • Full-range AS-i product portfolio for bus-based standard and safety technology from a single source

  • Consistent integration of AS-i devices by Siemens in the SIMATIC programming and diagnostics concepts and in the TIA Portal engineering framework

  • Integration of ASIsafe applications in SIMATIC safety programming (e.g. Distributed Safety)

  • Planning, calculation and verification of the entire safety chain on the basis of ASIsafe in the Safety Evaluation Tool (TÜV-tested)

  • Integration of subordinate AS-i networks in the PCS 7 process control system

  • Global spare parts logistics, consulting and service