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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AS-i variations

The right solution for each application:

AS-i supports perfect adjustability – to any system size and any safety requirement. Even to small applications with low power consumption.

AS-Interface – the powerful system for networks up to 600 m

The best choice for AS-i networks with large expansions and/or increased total current demand via the AS-i cable (30 V rated voltage).

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. 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
  • Topology: any, combinable, no termination resistors
  • Medium: 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

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, software tools (TIA Portal) and services.


  • 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 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

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 MSS 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 / Cat.4 / SIL 3
  • Full compatibility with all other AS-Interface components in accordance with IEC 62026-2


Mit den modularen SIMATIC AS-i Links auf Basis ET 200SP können AS-Interface Netze ganz einfach fehlersicher an Sicherheitssteuerungen angeschlossen werden, z.B. SIMATIC oder SINUMERIK. Als Bindeglied in der busbasierten Sicherheitstechnik sorgen sie für die Umsetzung der ASIsafe Telegramme in das PROFIsafe Protokoll – und das in beide Richtungen. Das Erfassen sicherer Signale erfolgt wie gewohnt mit den robusten ASIsafe Slaves. In der Steuerung erfolgt parallel zur Verarbeitung der Standard Daten die sichere Verarbeitung. Ergebnis der sicheren Verarbeitung sind sicherheitsgerichtete Abschaltbefehle der Steuerung, die über PROFIsafe an die sichere Aktorik z.B.  Motostarter übermittelt werden. Des weiteren können die sicherheitsgerichteten Signale zurück auf der ASIsafe Ebene weiterverarbeitet werden und z.B. zur Abschaltung sicherer AS-i Ausgänge in Verbraucherabzweigen genutzt werden.



SIMATIC AS-i F-Link - auf Basis SIMATIC ET 200SP:

  • Bei großen Mengengerüsten an sicheren Sensoren bzw. Aktoren
  • Bei einer umfangreichen und komplexen Sicherheitslogik
  • Bei einer Vielzahl sicherheitsgerichteter Abschaltkreise
  • Zur sicherheitsgerichteten Weiterverarbeitung auf der überlagerten Feldbus-Ebene

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

With AS-i Power24V, the already present power supply unit of your control supplies the field bus too! With network lengths of up to 50 m, the voltage is absolutely sufficient.


AS-i Power24V serves as automation expansion which is particularly suitable for compact machines (e.g. machine tools) and applications inside 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
  • Increased degree of standardization in small systems
  • Reduced getting-started costs for AS-Interface
  • Utilization of present AS-i network advantages, e.g. high data quality, extended diagnostics and maintenance information, integrated ASIsafe technology, 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.

The ASIMON PC software serves the configuration of the AS-Interface safety monitor. Vie the software's online function, the current state of the configured logic blocks can be read out on site and monitored in the fully graphical diagnostics view. The green/yellow/red color changeover of the blocks and connection lines provides the desired status information in an intuitive manner. This function offers valuable advantages particularly in terms of commissioning and troubleshooting.


The ASIMON V3 software offers numerous further user benefits, including fully graphical circuit diagram generation of the safety logics in transparent window technology, safe coupling of two AS-i networks, filtering of short-term one-channel interruptions in the sensor circuit, management of user- specific blocks, graphics printout of the safety logics, gradual teaching or manual entry of the ASIsafe code tables, freely selectable index assignment for integrated PLC diagnostics, immediate state signaling of relay outputs to the PLC and many further valuable functions.

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
  • DP/AS-i F-Link


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.