AS-Interface – the clever field bus standard

AS-Interface (AS-i) provides you with an effective and powerful bus system which connects all sensors and actuators on the lowest field level with the superior control – with unrivaled ease, safety and integration! AS-Interface serves as a cost-favorable feeder for PROFIBUS and PROFINET and supports easy engineering. It is standardized in accordance with IEC 62026-2. All components comply with the AS-i Specification and are correspondingly tested and certified. The AS-i standard is manufacturer-neutral.

Technical specifications for AS-Interface

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The right solution for each application:

AS-i supports perfect adjustability – to any system size and any safety requirement.

AS-Interface – the powerful system

The best choice for AS-i networks for universal application.


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 connected to the SIMATIC controller, SINUMERIK, or other controllers in a very user-friendly way: With the CM AS-i Master ST module in the ET 200SP for connection to all controllers and for any plant size. With the AS-i master module on the S7-1200 Basic Controller for smaller automation solutions. Or with the other AS-i master modules from Siemens for other applications. The integration is just as easy as with other expansion modules of the SIMATIC controllers.

Key data per AS-i network

  • Number of slaves: up to 62
  • Number of I/Os: up to 496 inputs and 496 outputs
  • Topology: any, as line, star, tree
  • Medium: unshielded two-wire line for data and energy
  • Line length: 100 m as a standard, extendable with repeater and extension plug
  • Cycle time: 5 ms (typical)
  • Data transfer: digital and analog values


Full-range solution provider

We offer a complete portfolio of AS-i components, from masters from SIMATIC, power supplies and slaves, all the way to system components.

The product range of AS-i slaves offers everything, 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.


  • Full-range AS-i product portfolio for bus-based standard and safety technology from a single source
  • Consistent integration of AS-i devices in the SIMATIC programming and diagnostics concepts and in the TIA Portal engineering framework
  • Integration of ASIsafe applications in SIMATIC and SINUMERIK safety programming
  • Integration of subordinate AS-i networks in the PCS 7 process control system
  • Global spare parts logistics, consulting and service

ASIsafe – integrated safety

The ASIsafe safety technology (AS-i Safety at Work) already forms part of every AS-i network and can be used and expanded by means of special ASIsafe components. This way, standard and safe data can be transferred on one and the same AS-i bus system –TÜV-certified, up to PL e / Cat. 4 or SIL 3. ASIsafe is scalable from small safety islands to system-wide Safety Integrated architectures with superior safe PLC.




  • Direct integration of safety-related components (e.g. EMERGENCY-STOP, protective door) in the AS-Interface network
  • The 3RK3 modular safety system supports the implementation of safety-related functions independently of the controller or also facilitates full integration in the safety control system using the SIMATIC AS-i F-Links
  • Attainable safety level up to PL e / SIL 3
  • Full compatibility with all other AS-Interface components in accordance with IEC 62026-2

The modular SIMATIC AS-i Links based on ET 200SP enables AS interface networks to be easily connected fail-safe to safety controllers such as SIMATIC or SINUMERIK. With the SIMATIC AS-i F-Links, the advantages of AS-i can also be utilized in complex safety applications. They facilitate the application of AS-Interface, for example under fail-safe SIMATIC or SINUMERIK controls. Acting as links in bus-based safety technology, they support the ASIsafe telegrams' transfer to the PROFIsafe protocol – in both directions. As usual, the detection of safe signals is realized by means of rugged ASIsafe slaves. The safe data are processed in the control in parallel with the standard data's processing. As a result of safe processing, the control issues safety-related disconnection commands which are transmitted to the safe actuators, e.g. motor starters, via PROFIsafe. Furthermore, the safety-related signals can be further processed back on the ASIsafe level, for example for the disconnection of safe AS-i outputs in load feeders.



SIMATIC AS-i F-Link - based on SIMATIC ET 200SP:

  • for large quantity structures of safe sensors and actuators
  • for expansive and complex safety logics
  • for a large number of safety-related disconnection circuits
  • for safety-related further processing on the superior field bus level

The ASIsafe Solution Local requires only few components: An MSS or a safety monitor and safe slaves. Neither fail-safe PLC nor special masters are required. The MSS monitors safe sensors (e.g. EMERGENCY-STOP), evaluates them in accordance with its parameterized safe logics and ensures their safe disconnection. Disconnection is realized in a distributed manner via ASIsafe in connection with safe AS-i outputs or via safe outputs integrated in the device.



MSS and safety monitors - the best choice:

  • with medium and small quantity structures of safe slaves,
  • with a small number of safe disconnection circuits
  • when safety technology and safety-related processing are to be separated from the superior field bus level or control in a targeted manner
  • with a manageable number of safe logical interconnections

AS-i Power24V – Savings of up to 50% with small applications up to 50 m

AS-i Power24V is used for particularly compact machines (e.g. machine tools) or applications in the control cabinet. The utilization of already employed 24V power supply units in connection with a data decoupling module facilitates the cost-favorable realization of AS-i networks with expansions of up to 50 m.


With the help of the data decoupling module, data and energy can be realized on a single line in the AS-i network. Even several data decoupling modules for multiple AS-i networks can be connected to one power supply unit – which results in an additional cost advantage.

  • Cost and space savings through elimination of the 30V AS-i power supply unit
  • Efficient utilization of one power supply unit for several AS-i networks
  • Reduced getting-started costs for AS-Interface
  • Utilization of present AS-i network advantages, e.g. high data quality, extended diagnostics and maintenance information, unlimited number of connectable slaves


The power supply units centrally supply the AS-i network and the connected slaves with energy. They form an integral part of an AS-Interface network and, in combination with data decoupling, facilitate the simultaneous transmission of data and energy on the same two- wire line.

Up to 62 standard slaves or 31 safe slaves can be connected to an AS-i network for data exchange with the superior AS-i master. Our portfolio of AS-i slaves ranges from simple I/O modules down to motor starters and frequency converters.

AS-Interface networks can be very comfortably directly connected to the SIMATIC control or Distributed I/0s. For this purpose, so-called CPs or CMs are available. Integration is just as easy as with other expansion modules of SIMATIC.

Depending on your individual requirements, you can chose between the "small" ASIsafe Solution local and cell-spanning, system-wide ASIsafe integration with the help of the SIMATIC AS-i F-Link as gateway between ASIsafe and PROFIsafe beneath a fail-safe control.

Besides direct integration, AS-Interface can also be employed in a distributed manner as feeder for superior bus systems. With the help of AS-i gateways (links), subordinate AS-i networks can be completely assembled and commissioned even before the central control is completely programmed.

Our portfolio of system components comprises products for AS-i network analysis, AS-i slave addressing as well as range extension. Numerous further accessory components such as distributors, M12 feeders, mounting plates and cable end pieces complete the product portfolio and support a very easy and flexible assembly of the entire AS-i system.


From SIMATIC STEP 7 V5.4, AS-Interface modules can be configured in your system with even greater comfort. STEP 7 comprises a slave selection dialog via which the modules are integrated in the respective S7 project with a mouse-click. All slave-specific profile settings (I/O and ID codes) are automatically carried out. The modules are parameterized via selection lists, no more searching for parameter bits in the operating instructions. A comprehensive module description text eases system documentation.

The MSS ES parameterization software forms a central part of the modular safety system (MSS) and supports the rapid and easy parameterization of safety functions as well as comprehensive diagnostics options.

AS-Interface provides comprehensive diagnostics data which can be effortlessly and immediately read out by the SIMATIC STEP 7 system. These data can be interconnected in the STEP 7 program for responding to system states and/or output on an operator panel for rapid fault rectification.


For this purpose, a fully functioning package of function blocks for S7-300/400/1200 and pre-defined screens for the color graphic displays in 6", 8" (10") and 15" version are available. The screens can be scaled via WinCC for other monitor sizes. The graphics comprise the diagnostics of AS-i master and slaves.


STEP 7 V5.5 / WinCC flexible

The following AS-i masters and links are supported:

  • CP343-2 (P)
  • IE/AS-i Link PN IO
  • DP/AS-i Link Advanced
  • DP/AS-i Link 20E


STEP 7 V11 SPS2 / WinCC V11 SP2

The following AS-i masters and links are supported:

  • CM1243-2
  • CP343-2 (P)

Application descriptions

SIMATIC controllers with an integrated PROFINET interface offer web server functionality and enable diagnostics from any location via an Industrial Ethernet Network. Any web client, such as a PC, Multi Panel or PDA, can obtain read-access to module, program and diagnostic data from a standard internet browser. User-specific websites allow users to implement a continuous-diagnostics concept.


Application descriptions

The AS-i function block library for PCS 7 is integrated in the SIMATIC PCS 7 process control system and expands it for integration of the AS-Interface system. As the result, the advantages of AS-Interface such as the considerable reduction of wiring outlay for distributed actuators/sensors and very simple installation can also be used in a system based on PCS 7. The library contains modules for accessing the I/O data of AS-i slaves, modules for diagnostics of the AS-i system, and a faceplate for the PCS 7 Maintenance Station.

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