AS-i = flexible: The two-wire line can be flexibly routed – just like any ordinary electric cable! Whether in line, star or tree topology. Up to 62 stations can be connected to every AS-i network over a length of up to 600 m. Another flexible feature: The open AS-Interface standard facilitates investment protection without having to commit yourself to one specific manufacturer in the long term. Flexible selection in terms of safety: With ASIsafe Solution Local or ASIsafe Solution PROFIsafe – we offer safety technology for small to large applications.

Flexible topologies

Whether line, star or tree layout – there are no restrictions in terms of structure or network topology thanks to the rugged functional principle. AS-Interface facilitates your installation technology’s optimum adjustment to individual systems or machines and supports ample savings in terms of planning, configuration, mounting as well as time. Also expansions can be carried out more easily and rapidly. Where control lines had to be routed before, now only one yellow AS-i cable has to be wired.

Open standards

AS-Interface is standardized in acc. with EN 50295 and IEC 62026-2. All components by Siemens comply with the AS-i Specification and are correspondingly tested and certified. This ensures the perfect interaction of Siemens products with third-party devices.
Furthermore, a certified standard which supports the application of safety-related components in the AS-Interface network was developed with “AS-i Safety at Work”. The “Safety at Work” concept has been certified by the TÜV (German Technical Inspectorate) and by the German social accident insurance’s institute for occupational safety.


AS-i networks can be easily adjusted to system expansions as AS-Interface is accurately matched to the requirements of the lowest field level: Realtime capability, low data volumes and a large number of connected devices – in addition to the already mentioned benefits of freely selectable topology and innovative insulation piercing method.
An AS-i network can be expanded to up to 62 AS-i slaves. In terms of simple I/O modules, this corresponds to a maximum of 992 I/O points, distributed to a bus length of up to 600 m per AS-i network.
Also analog values, e.g. of analog modules or measuring transducers, can be integrated just as easily as digital I/Os. The AS-i master automatically organizes the transfer of all data. This way, a small field bus can be effortlessly expanded and flexibly adjusted to machine or system changes.

Safety technology

The “ASIsafe” technology already forms part of every AS-i network and can be used by means of corresponding safety related components right away or in the future. Such components may comprise fail-safe I/O modules, position switches, E-STOP pushbuttons, safety monitors or the 3RK3 modular safety system for safe processing and logics as well as safe AS-i gateways (F-link) for connection to a superior fail-safe control.
Only with Siemens solutions are subordinate safe AS-i networks incorporated in Safety Integrated and thus become part of fail-safe programming via SIMATIC. And only Siemens offers the choice between the “small” ASIsafe Solution Local with targeted separation of safety technology and operational control and the “large” ASIsafe Solution PROFIsafe, i.e. the bundling of standard and safety technology within the control on the basis of Safety Integrated.
Both solutions offer benefits in terms of easy safety function calculation and evaluation via the Safety Evaluation Tool (SET), minimized engineering expenditures and comprehensive diagnostics – for maximum machine and system availability.