FAQ – Questions and Answers about AS-Interface

Here you can find an overview of frequently asked questions about our products as well as about AS-Interface, ASi-5 and IO-Link.


Are you unable to find the answer to your question? No problem, of course we will gladly answer your individual questions via phone or e-mail. If you have any technical questions, our technical support team will be happy to assist you.


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Product search & Information

What is „Bihl+Wiedemann's Choice“?

The "Bihl+Wiedemann's Choice" range consists exclusively of best-practice products that combine the highest level of user experience, are nearly always in stock in large quantities and can usually be shipped right away. "Bihl+Wiedemann's Choice" items are suitable for almost all standard applications and are also very attractively priced thanks to the quantities produced. We have introduced the "Bihl+Wiedemann's Choice" labeling to provide our customers with a quick decision-making aid while clearly highlighting what advantages the respective product has for the customer.


Where can I find GSD files?

We provide corresponding device description files (GSD files) for all Bihl+Wiedemann Gateways . These are available as a ZIP file in the "Downloads" tab on the product detail pages of the devices.

Please register or log in to download the file.


Where can I find EDS files?

We provide corresponding device description files for all Bihl+Wiedemann Gateways. The EDS files for EtherNet/IP Gateways are available as a ZIP file in the "Downloads" tab on the product detail pages of the devices. 


Please register or log in to download the file.


Where can I find parameter libraries, such as SISTEMA

Here you can download the current parameter library for calculation tools (SISTEMA and others) as a ZIP file: 


Parameter library


Please register or log in to download the file.


Where can I find EPLAN macros?

We provide EPLAN macros for most of our products. These can be found as a ZIP file on the product detail pages within the "Downloads" tab under the "EPLAN Macros" sub-item.


Please register or log in to download the file.


Where can I find manuals/instructions?

We provide various manuals to help you commission and use our devices. Guides and manuals can be found on the product detail pages within the "Downloads" tab. For every item, we provide various documents as PDF and sometimes also as a video tutorial, including:


Please register or log in to download the files.


Some of the files are only visible after logging in.


Which devices are suitable for OSSD signals?

We provide a wide range of safety I/O modules for the connection of OSSDs (optoelectronic protective devices), floating contacts, and antivalent switches in IP20 and IP67 versions. You can find an overview of corresponding products here:


To the Safety I/O modules


We are happy to provide you tailor-made solutions and special variants for your sensors on request.


Tel.: +49 621 33996-0

E-Mail: mail@bihl-wiedemann.de

Questions About the License of the Bihl+Wiedemann Software (Safety) Suite

How can a license be moved to a new computer?

To move the license to a new computer (e.g., when switching employees, replacing hardware components, changing computers) you can perform the following steps:

  1. Note down the operating mode under which the software was installed.

The operating mode determines whether the software can only be installed on one permanently assigned computer (“single-user license”) or whether it may be installed (but not operated simultaneously) on several computers by means of a floating license.


If you do not know the operating mode, you can read it on the upper bar in the license manager: “License Manager” without suffix indicates the “Single-User License” operating mode, whereas the name “License Manager – Floating Operating Mode” indicates the floating variant.


2. Please delete the existing license from your previous computer using the license manager.


3. Install the software on the new computer:

You will find the download link and the voucher code in the respective PDF file, which you received together with the software (an automated email is additionally sent with the registration data to the specified email address after the first registration).


4. Install the software with the same operating mode that was selected during the initial installation (see above), either as a “Single-User License” or as a “Virtual Machine Option” (i.e., floating license).


What should be done if the license data has been forgotten?

After registration of the Bihl+Wiedemann Suite, you receive a confirmation email, which contains your registration data.

If you want to request your data again, you can obtain it by clicking the “License data forgotten?” button in the registration window. If you have any further issues, please contact our First Level Support at +49 (0)621 33996 449 for further assistance.


When I open the Bihl+Wiedemann Suite, the following message appears: “Valid, license data incomplete” with a yellow exclamation mark. What can I do?

If the above message appears, the license data has not been completely saved on your computer. You have to enter the license data again to verify your email address. The software continues to function as usual. This way, we can provide you with faster and easier support in the event of a request or problem, e.g., for a specific software or firmware version.


During registration, the message “This voucher code has been registered for a different operating mode” appears. What can I do?

If you are trying to install an existing license on another computer, it is crucial to use the operating mode selected during the first installation for registration. The license is only valid in the originally selected operating mode (for the different operating modes, see also here).


The only workaround is to completely uninstall & reinstall the software, taking care to select the “Standard installation option” or “Virtual machine option” checkbox. The installation file can be kept.

What should be done if the message “No connection to Bihl+Wiedemann server” appears during registration?

If this exists, check whether filters for specific pages and/or specific content and objects are set in the firewall settings of your company network and/or in your personal firewall settings.


1. The requests are made as JSON objects by HTTPS POST via TCP port 80 and 443.
2. The requests are sent to licensing.bihl-wiedemann.de.


Your firewall or filter settings must allow these requests.

Commissioning & Configuration

Should I use a command interface to set up the ASi circuits?

We recommend using the Bihl+Wiedemann Software Suite with integrated hardware catalog to set up your ASi circuits.


If you have questions or encounter problems with the command interface, please contact our support team.


Tel.: +49 621 33996-0

E-Mail: asiexpertbihl-wiedemann.de


How are safe code sequences generated in ASi-3 Safety modules and what happens in the monitor when teaching them in?

The code sequences used in the ASi-3 Safety modules are assigned to us by the AS-Interface organization AS-International and then programmed into the modules by us. When teaching in a module, the code sequence specifically implemented there is announced to the safety monitor. The validity of the code sequence is also checked. This process is defined in the ASi Safety at Work specification and certified as a procedure.


How is the release code (checksum) created during verification of the security configuration?

The release code is a checksum calculated using the complete data of the security configuration. The calculation method is defined in the ASi Safety at Work specification and certified as a procedure.


Why is the "gap" between the upper and lower part of the module completely normal for mounted IP67 modules as well as active distributors and passive distributors?

When you screw the upper and lower parts of the module together, the contact pins are closed firmly and tightly - by compressing the rubber material between the housing parts. The contact pressure defined in the piercing technology enables the IP67 protection class to be safely achieved with just one screw. This seal creates an optical gap between the upper and lower parts of the module. This is completely normal and has no influence on the achievement of the protection class.


What does it mean if the message "1.xx - Test! ..." appears on the display of the gateway, or if the node flashes yellow in the safety diagnostics?

A test request (on the gateway's display) or the yellow flashing (in the ASIMON360 software and/or directly on the module) means that only one of the two (2 channel) inputs of the ASi node was closed within the set synchronization time.


The most common cause is when the synchronization time is set too short. A sudden jolt of the contacts can also cause this to happen. This can be remedied by selecting the “double channel dependent with filtering” block type and activating the “Switch-off without test request” option.


The test request can be acknowledged by re-activating the corresponding EMERGENCY STOP button or door switch.


In rarer cases, the causes of a test request or the yellow flashing are:


  • a short Zero sequence (less than 8 ASi cycles),
  •  the node is not taught-in or the node has a code sequence error (e.g., F sequence) and the monitoring device is configured in the “double channel independent” block type. In these cases, testing is not effective!


Can gateways and IP20 modules also be installed and operated horizontally?

As a general rule, we recommend a vertical installation position as described in the installation instructions. The horizontal installation position hampers the dissipation of heat from the housing (formation of hotspots). This increases the derating by an average of approx. 20 °C (module type-dependent). A module designed for a maximum of 70 °C, for example, would thus only be allowed to operate in a maximum ambient temperature of 50 °C. Depending on the module type, the increase in temperature can be even higher.


It should also be noted that in the case of a horizontal installation, the dissipating heat rising from the lower modules would add additional heat load to the modules adjacent to the top (formation of hotspots).


Which ports are needed for a VPN connection with ASi Control Tools360/ASIMON360?

Our software – ASi Control Tools360, ASIMON360, diagnostic software – requires UDP ports 57 and 87 to connect to our gateways.


How can I easily find out if the 4 A decoupling coils in the gateway are sufficient for my ASi circuit?

The safest way is to use a gateway with 4 A decoupling coils, together with a 30 V power supply, for testing and commissioning. The gateway measures the current in the ASi circuit while the machine or system is running. Either directly on the display of the gateway or via the online bus information in the ASIMON360 software (or ASi Control Tools360 software), both the actual measured current and the maximum current after Power On can be read. The information is given with a 100 mA resolution.


Which Performance Level (PL) does the ASIMON360 Software achieve?

The ASIMON360 software has no performance level (PL) assigned to it because it does not form an active part of the safety chain, e.g., between an E-stop input and a safe output. The ASIMON360 can be used to configure certified functions within the safety monitor. The ASIMON360 is only a necessary tool for configuration, comparable to using a screwdriver to change the position of a DIP switch on a safety relay to configure it for a specific function. In both cases, the ASIMON360 and the screwdriver are merely aids for configuration, without playing their own part in the safety chain and therefore without having any influence on the performance level.


The ASIMON360 is the graphical interface for configuring the safety functions (up to PLe). The transmission of the configuration to the safety monitor is secured by the release code and is additionally validated in the safety monitor.


What is the difference between ‘MTTF’ and ‘number of switching cycles’ when referring to safe outputs?

The MTTF (Mean Time To Failure) value indicates the average time a device can be operated before it fails. Since this is rather dependent on the number of switching operations than on the age of components subject to wear, such as a relay, the ‘number of switching cycles’ is the decisive factor in this respect. The mean time to failure is much longer for infrequent switching than for frequent switching.


Which devices do we recommend when designing a new system or revising an existing machine?

When designing a new system or revising an existing machine, we always recommend using the latest and most powerful devices. You can easily find them by using the product selectors on the Bihl+Wiedemann website. The actual devices from the product selectors not only offer all the advantages of older Bihl+Wiedemann devices, they also feature a variety of new functions and convince with an impressive price/performance ratio.


Why is it always advisable to use both grounding connections on the ASi Gateway?

The reason is that it is in your best interest to ground the device through both grounding connections. Whereas grounding via the grounding screw grounds the housing (EMC), grounding via the terminal is the shortest path to the circuit board (e.g., for the ground fault monitor function).


Please also refer to chapter 'EMC/Grounding' in the ASi installation recommendations


How many motorized rollers can be compensated for overvoltage by a single brake chopper?

Our 24 V brake chopper BW4915 or 48 V brake chopper BWU4969 is able to compensate for overvoltage of at least two motorized rollers at the same time. In general, it is almost impossible to accurately calculate the amount of energy fed back, the system behavior, and the number of brake choppers needed. This is because there are too many influencing factors involved in the whole energy chain, e.g., the power supply, the motor driver and the load. In practice, it has been found out that additional brake choppers can simply be connected until no error message is generated during braking.


Where can I find more information about Commissioning  & configuration?

How to easily realize your ASi installation, as well as answers to many other questions about product selection and commissioning of ASi networks can be found here.


Bihl+Wiedemann's best practice

Diagnostics & Troubleshooting

The message „Fatal Error“ appears on the device display. What can I do?

Please contact our support team. Our product specialists will be happy to assist you.


Tel.: +49 621 33996-0

E-Mail: asiexpertbihl-wiedemann.de


The message "Earth Fault" appears on the device display. What can I do?

The earth fault monitor checks the symmetry of the ASi voltage. If the ASi voltage is no longer symmetrical, it means that there is limited immunity to interference during data transfer.


Earth fault checklist

Here you can find an "Earth Fault Checklist " in PDF format:


Earth fault checklist


Please register or log in to download the files.


If you encounter problems or uncertainties in handling this message, please contact our support team. Our product specialists will be happy to assist you.


Tel.: +49 621 33996-0

E-Mail: asiexpertbihl-wiedemann.de


My gateway is heating up, is it normal?

Yes, a perceived high temperature is normal and completely safe. The housings are made of stainless steel and unlike plastic housings, they have good thermal conductivity. Therefore, they serve as heat sinks for the electronics.

What do I have to take in consideration when replacing a defective node?

The replacement device must have the same part number. You can then replace the defective node  without using a hand-held addressing device or additional programming work. The additional steps necessary depend on the slave type used (e.g. standard or safety). You can find more information in our video tutorial.


If you encounter problems or issues related to this topic, please contact our support team. Our product specialists will be happy to assist you.


Tel.: +49 621 33996-0

E-Mail: asiexpertbihl-wiedemann.de


What do I have to take in consideration when replacing a defective master?

The replacement device must have the same part number. You can then replace the defective master without additional programming work. Please attach to the following necessary steps:


  1. Disconnect the defective safety monitor from the power supply and from the ASi network.
  2. Remove the chip card from the top of the defective unit and insert it into the replacement unit.
  3. Connect the new monitor to the ASi network and the power supply.
  4. The display menu of the monitor willguide you through the copying process to help you transfer the stored configuration from the chip card to the device.
  5. You may be asked to specify the direction in which the copying process is to be started – in this case, select "Chipcard > Master".
  6. Enter the release code of the configuration and confirm this code. The safety monitor then starts and the transfer is completed.

The above steps are described in detail in our video tutorial.


If you encounter problems, please contact our support team. Our product specialists will be happy to assist you.


Tel.: +49 621 33996-0

E-Mail: asiexpertbihl-wiedemann.de


Is it possible to transfer the configuration from one gateway to another gateway (with different article number)?

No. Configuration transfer is only guaranteed between gateways with the same article number. Likewise, it is not possible to transfer the configuration between other manufacturers and their gateways to Bihl+Wiedemann gateways.

If Bihl+Wiedemann gateways with the same article number are used, transfer by means of a chip card is quick and easy. Instructions for this can be found in our video tutorial.


The second ASi circuit of a PROFINET (PROFIBUS) gateway with a double master is not used. Then why does the PLC give error messages?

This is due to the settings in the control system for ASi circuit 2. The error messages for ASi circuit 2 can be switched off by making a few simple changes:

  • Do not select your data from the ASi circuit 2 through the device description file in the control system.
  • Set ASi flags for C2 (ASi circuit 2) under GLOBAL (device-specific parameters) to "not in Diagnosis". 
  • Set the following flags under GLOBAL (device-specific parameters) for the external diagnostics of ASi circuit 2 to "disable":


    • ExtDiag on Config Errors
    • ExtDiag on AS-i Power fail
    • ExtDiag on Peripheral Faults
    • ExtDiag on Earth Fault
    • ExtDiag on double Address


Which device should be used to replace a defective ASi Gateway – which one is recommended?

If you want to replace a defective ASi Gateway or an ASi Gateway with integrated safety monitor, we always recommend that you use a replacement device with the same article number. This is the only way to ensure simple device replacement by exchanging the chip card. On the other hand, we do not recommend using newer devices or their successors as replacement devices.


Where can I find more information about diagnostics & troubleshooting

The Troubleshooting Guide enables quick and easy error detection and at the same time helps with troubleshooting.


Please register or log in to view the content.


Troubleshooting guide

Firmware Update

How can I perform a firmware update on Bihl+Wiedemann components?

To update the firmware of an ASi-5 device in the field, you need the Bihl+Wiedemann Firmware Update Tool. This is included in all Bihl+Wiedemann Software Suites. The tool enables the firmware status of all connected devices to be compared against the latest version on the server and update the firmware if necessary. The integrity of the firmware is ensured at all times thanks to the end-to-end encrypted connection to the Bihl+Wiedemann server. This also effectively prevents manipulation of the devices by malicious firmware.


Our recommendations for a smooth process:

  • Leave the master's chip card in the device during the update
  • Back up the data on the devices prior to the update
  • Your system should not be operating during the update. This is because the devices are restarted in the course of the update and output data is consequently reset.
  • If an update is available for the master, it is mandatory that this is installed before updating the nodes. The software guides you through all the necessary steps.


What makes the firmware update for Bihl+Wiedemann components so (cyber)secure?

The update process at Bihl+Wiedemann components follows the premise: System integrity must always be guaranteed.


Data integrity is a widespread basic requirement in automation systems. However, with increasing networking of devices, this requirement is no longer sufficient. Instead, the integrity of the entire system must be guaranteed, not only the transmission, but also the software or firmware of the individual components.


ZVEI e. V., (Verband der Elektro- und Digitalindustrie -German Electrical and Electronic Manufacturers' Association), has summarized in a white paper what is important when it comes to integrity

  • Updates play an important role in eliminating security-relevant vulnerabilities in components
  • Updates must be checked for integrity and authenticity before they are implemented (especially to rule out changes by possible attackers)
  • If the integrity is breached, the update must not be applied.
  • Simple checksums do not offer any protection against intentional changes by attackers, as they can also be manipulated.
  • Signatures or key-based cryptographic hash functions effectively protect against checksum modification

Our measures consistently take into account the specifications of ZVEI. How we reliably ensure your security in the update process:

  • Certificate-based end-to-end encryption between the update server and the device to be updated.
  • End-to-end encryption prevents the infiltration of malware into Bihl+Wiedemann devices
  • Comparison with the server ensures the detection of outdated firmware versions
  • The TÜV-tested procedure is also approved for firmware in safety products


Can I also perform a firmware update of functionally safe components in Bihl+Wiedemann products?

Yes, it is also possible to update safety-relevant firmware in the field by means of a TÜV-approved process. To accomplish this, use our firmware update tool and an end-to-end encrypted connection to the Bihl-Wiedemann server. In this way, we not only ensure the integrity of the firmware in the devices. But also which device is working with which firmware version at any time will be known. This is the only way to fulfill the legal obligation to quickly inform about potential, safety-relevant functional deviations of affected devices.


Is it possible to import an older firmware version via firmware update (firmware downgrade)?

No, a downgrade or an “update” to an outdated firmware version is not possible and also not recommended. Updates at Bihl+Wiedemann are typically always downward compatible, so that existing applications can remain unchanged. However, they usually contain useful improvements in terms of functionality, stability and security mechanisms.


Where can I find more information on how to perform a firmware update?

Under “Installation tips” you will find a step by step PDF guide on how to perform a firmware update.


More information

Questions about further subjects

Questions about AS-Interface


Which facts and data are known about the AS-Interface market?

  • Over 40 million ASi devices in use worldwide
  • Over 7 million of them are safety devices
  • More than 2,000 certified products
  • Almost 70 % growth with regard to safety-oriented devices


What is an ASi Master?

The AS-Interface master connects sensors and actuators to the higher-level control via the ASi modules. With the ASi Master, digital and analog data that has been gathered decentrally by ASi modules, can be transferred to the higher level control through the respective bus system. The output signals of the controller are transmitted then through ASi to the actuators in the field.


More about ASi Master


What is an ASi node?

ASi nodes are connected to the ASi Master with a cable. They are used to integrate the sensors and actuators into the ASi network, regardless ifinside the switching cabinet or in the field. These are connected to the power supply and data communication in the ASi network. Each node is assigned to a unique address in the network.


More about ASi nodes


How does addressing of ASi nodes work?

There are several ways to address an ASi node:


  • Convenient and largely automated addressing via Bihl+Wiedemann Software
  • Automatic addressing when faulty ASi nodes are replaced


Which addresses are available for addressing ASi nodes?

Addressing of ASi-3 nodes

With ASi-3, there are 31 ASi addresses available, whereby each address may only be allocated once. A distinction is made between standard addressing and extended addressing. The addressing mode of ASi participants is determined by the manufacturer. With standard addressing, each ASi participant reserves a full address (1...31). With extended addressing, each address can be reserved by two ASi participants (1A...31A, 1B...31B). It is not possible to address an ASi node with standard addressing and an ASi participant with extended addressing on the same address, e.g. 3 and 3A or 3B.


Addressing of ASi-5 nodes

With ASi-5, the nodes are assigned an ordering number starting from 1. The numbering takes place sequentially.


What is an ASi power supply?

In conventional design, a separate ASi power supply (with integrated decoupling coils) is required for the voltage supply of each ASi circuit. With ASi gateways and safety monitors of the version "1 power supply, 1 gateway for 2 ASi circuits, cost-effective power supplies" by Bihl+Wiedemann, the decoupling coils are already built into the devices. This enables the supply of two ASi circuits by means of one standard 30 V power supply.


With short cable lengths, even a standard 24 V power supply can be used. This is an optimal solution for small and very small systems – i.e., for small machines with 3 to 15 ASi nodes and a maximum cable length of 50 meters. We have an affordable line of ASi gateways, optimized for 24 V applications.


More about ASi power supply


What is an ASi distributor?

ASi distributors enable simple connection of various sensors and actuators to ASi anywhere in the field over an M12 connection. Active distributors are required for sensors and actuators without an integrated ASi chip. Passive distributors are suitable for sensors and actuators with an integrated ASi chip.


What is an ASi bus termination?

The total length of the ASi standard network is limited to 200 m for ASi-5 and 100 m for ASi-3. When determining the total length, all junctions must be included in the calculation. The ASi bus termination is a cost-effective module for extending the cable length in an ASi-3 network up to 200 m.


How and when does an ASi bus termination help?

For mixed ASi-5/ASi-3 circuits, we recommend an additional ASi bus termination if the cable length is approx. 70 m or longer. The ASi bus termination can help improve the ASi-5 communication.


What is an ASi repeater?

The total length of the ASi standard network is limited to 200 m for ASi-5 and 100 m for ASi-3. To determine the total length, all junctions must be included in the calculation. The ASi repeater is a module for cable extension. It makes it possible to increase the cable length in an ASi-3 network up to 200 m. Areas with strongly impaired EMC can thus be bypassed. ASi repeaters cause a certain delay in the transmission of telegrams.


More about ASi circuit extension


What is the future potential of AS-Interface or ASi-3

ASi-3 is a proven and stable technology with a wide range of available products. However, ASi-3 continues to be a future-proof technology whose possibilities are far from being exhausted. In the course of digitalization and Industry 4.0, it is now necessary to retrieve more and more data more quickly from the field level - in order to subsequently process them in higher-level instances. ASi-5 was developed for this requirement: The latest ASi generation offers a correspondingly high data bandwidth and short cycle times.


ASi-3 and ASi-5 are compatible with each other and complement each other optimally. Depending on the application or requirement, it must be checked individually which ASi technology is when the most appropriate or most economical. In practice, there will mostly be applications in which both ASi technologies are used. ASi-5 will therefore not replace ASi-3.


Are fuses allowed in the ASi circuit?

An electronic, self-resetting fuse is included for each ASi circuit in all gateways with integrated decoupling. In most gateways, this fuse can be set by the user in 0.1 A steps for each ASi circuit. Further fuses are usually not necessary in the ASi circuit.


The use of circuit breakers and/or residual current circuit breakers in the ASi circuit is not recommended. Circuit breakers and residual current circuit breakers strongly interfere the ASi communication or, in the worst case, they prevent it completely. As a rule, slow-blow fuses have no negative influence on ASi communication as long as the diagnostic software confirms fault-free ASi operation after a slow-blow fuse has been used. This applies both to gateways with and without integrated decoupling.


In case that an external fuse is required, Bihl+Wiedemann has developed the power limiting module BWU4189. The power limiting module has been specially developed for use in ASi circuits and has no negative influence on the ASi communication.

Questions about ASi-5


Is ASi-5 a completely new technology?


No. ASi-5 is the evolution of the well-proven AS-Interface standard. ASi-5 offers all the advantages that have already made ASi so special in the past. For example, power and data are still transmitted over a single cable, you have free choice of your topology and the safety technology is still on the same infrastructure. The main reason for evolving ASi was the fact that Industry 4.0 and increasing digitalization brings with it ever greater volumes of data. ASi-5 has both a large data size and short cycle times, making it possible to transport more and more data, without restrictions, to where they can yield valuable information.


Is ASi-5 compatible with earlier ASi generations?

Yes. ASi-5 is compatible with all earlier ASi devices and components, meaning that ASi-5 nodes can be combined with ASi nodes of any generation—in existing as well as in new ASi networks. In an existing ASi network, you can simply connect additional new ASi-5 slaves and easily continue to use existing ASi nodess. To use ASi-5 nodes all you need is a new Bihl+Wiedemann ASi-5 / ASi-3 gateway.


Why is there no ASi-4?

ASi-3 directly follows ASi-5. “Skipping” ASi-4 illustrates that this development step is really big. In addition, we did not want to suggest that Industry 4.0 is the sole innovation driver for the new ASi generation.


When does it pay off to switch to ASi-5?

In particular for applications with high transmission speeds or high data volumes. In addition, in places where a concentrated and cost-efficient collection of a larger number of inputs and outputs is needed. In many cases, Bihl+Wiedemann’s new digital ASi-5 modules can be an affordable alternative to other fieldbus solutions.


Does ASi-5 still provide interoperability?

Yes. AS-Interface remains a standard ensuring compatibility with components from any manufacturer. All certified products with an ASi logo can interoperate in a common network.


Do ASi-5 networks need special software?

No. In principle, they can be configured without software but we always recommend the more comfortable option using our software solutions. Our software Suite enables you to easily plan, configure and parameterize ASi networks with or without safety. If you already use the software for your ASi network, all you need is a free update to be able to continue using it for ASi-5 applications. The software is as intuitive and comfortable to use as with ASi-3. An integrated hardware catalogue encompasses the complete ASi product range. All you need to do is click the device you need when configuring the ASi circuit. The new online bus information also enables you to easily address slaves and monitor inputs and outputs. This function makes it even easier to integrate IO-Link sensors.


Who developed ASi-5?

Like all ASi generations, ASi-5 is a joint development of several manufacturers of AS-Interface products. The complete project took more than 200,000 developer hours, evolving the idea of a new ASi generation into a mature trendsetting technology. Now that the main project has been completed, the involved companies continue to work on standards and certifications for new ASi-5 products.


How many ASi-5 nodes can be connected?

By combining ASi-5 and ASi-3 slaves on one ASi circuit, it is possible to connect at least 62 nodes – in many cases, even considerably more.


The Bihl+Wiedemann hardware catalog tells you how many ASi nodes can be connected for specific applications. It is integrated in our ASIMON360 and ASi Control Tools360 software. So a warning appears if the maximum possible number of ASi-5 and ASi-3 slaves is exceeded. In addition, vacant ASi-5 transport channels can be shown at any time when planning.


Our experts will gladly answer any further questions you may have.


Why does ASi-5 and IO-Link go so well?

Already during the development of ASi-5 we made sure that IO-Link will be perfectly embedded in ASi-5 and our user-friendly PC software - from the device to the PLC or cloud.

Our mature concept enables IO-Link data to be transmitted transparently via ASi-5. The fieldbus-independent solution combines the advantages of IO-Link and ASi-5, allowing up to 64 ASi-5 modules, each with 1, 2, 4 or 8 IO-Link ports, to be connected to an ASi-5 master. The maximum possible data frame of an IO-Link device (32 bytes) can be mapped without any problems.

Thanks to ASi, you also benefit from drastically reduced wiring effort without swichtes, great freedom in the choice of topology, and a smart power supply concept.


You can find more information here.


Questions about ASi-5 Safety


Why Use ASi-5 Safety?

There are already many different safety controllers and solutions on the market, but unfortunately the same is also true for the number of functionally safe protocols used and the fieldbus itself.


Fieldbus independence has always been a great strength of ASi and ASi Safety. There are gateways for almost all relevant fieldbuses and safety protocols. This makes the system architecture at the I/O level completely independent of the used controller, which means that it can be standardized across all applications.


Needless to say, this advantage also applies to ASi-5 Safety. Just as with the introduction of ASi-5 in the standard area, ASi-5 Safety also offers many new options. The higher data bandwidth and extended diagnostic and parameterization options are ideal for resource-intensive applications. 

This for example, makes the future implementation of IO-Link Safety possible.


What is the difference between ASi-5 Safety and ASi-5?

ASi-5 Safety has been an integral part of ASi-5 from the very beginning: both use the same communication technology. In the case of ASi-5 Safety modules, only the normatively required protection of the data is added - with an additional checksum.This makes the transmission of these signals functionally safe up to SIL 3/PLe. This is essential whenever standards require such functional safety to protect people and the environment.


Does ASi-5 meet the requirements of ISO 13849-1 and IEC 61508/62061?

Just like ASi-3 Safety at Work, ASi-5 Safety was once again tested and certified externally according to applicable functional safety standards. Similarly, the process used for ASi-5 Safety achieves a performance level up to PLe according to ISO 13849-1, or a safety integrity level up to SIL3 according to IEC 61508/62061.


Is it possible to connect standard sensors to ASi-5 Safety modules?

Of course, even standard sensors can be connected to ASi-5 Safety modules. With many modules, it is even possible to reconfigure connections so that the signal of the standard sensor is only transmitted via the standard protocol. This especially conserves communication resources such as addresses and bandwidth for ASi-3 Safety modules.


An additional advantage of ASi-5 Safety is that many safe and standard signals can be connected and transmitted over a single address. This saves resources and above all costs.


How does ASi-5 Safety perform in terms of Cyber Security?

The topic of cyber security is more relevant than ever. In the industrial sector, the reliability of processes and production in particular is becoming increasingly important.


Like the standard ASi-5 communication, ASi-5 Safety is almost tap-proof due to the nature of the system. The reason:  the data transfer via OFDM with dynamic frequency assignment,makes it very complex to capture the exchanged messages. This requires the entire context of the connection set-up between ASi master and ASi node. Besides, the clock frequencies must be precisely synchronized just like between the ASi master and ASi node according to the ASi-5 protocol.


Cyber security is also enhanced by the fact that the gateway creates a logical break between TCP/IP, ASi-5, and ASi-5 Safety. This means that high safety requirements only need to be placed on the ASi-5 Master, which establishes the connection to TCP/IP. ASi-5 modules, on the other hand, are much less problematic in terms of safety, since they cannot communicate over TCP/IP networks. Those responsible for network security can thus focus on significantly fewer devices and check them more carefully.


Can defective ASi-5 Safety devices be replaced as easily as standard ASi-5 devices?

Like ASi, ASi-5 Safety is characterized by maximum stability and availability. Defective masters can therefore be replaced easily and without complications: Thanks to the backup in the ASi master, the replacement device is automatically addressed and parameterized just like the original device.


What cycle times does ASi-5 Safety achieve?

ASi-5 Safety is very flexible: depending on the profile and application scenario, 1 to 64 safe process data along with additional standard  – each bidirectional – can be exchanged with one module. In the process, cycle times of up to 1.27 ms can be achieved for up to 16 safe inputs and 16 safe outputs each. Available diagnostics and acyclic services have no influence on the cycle times.


Which data can be transmitted with ASi-5 Safety?

As an integral part of ASi-5, ASi-5 Safety can transmit safe and standard data simultaneously. Up to 32 bytes are available cyclically for this purpose. The safe data always has a 1-byte checksum, which enables safe communication up to level SIL3/PLe. As with pure ASi-5 standard modules, there is also a diagnostic and an acyclic channel. This also allows ASi-5 Safety modules to transmit detailed diagnostic messages in case of an event. An additional high-performance method is also available to read out additional information if required – e.g., for predictive maintenance or similar applications.


What additional information (e.g. diagnostics) is available thanks to ASi-5 Safety?

ASi-5 Safety uses the same mechanisms as all other ASi-5 modules. This means that it provides cyclic data along with an event-based diagnostic channel and an acyclic channel for reading out numerous indices. These indices cover a wide range of information: manufacturer, model name, the ASi ID for unique identification, module temperature, measured currents or an hour meter, to name a few." OPC UA enables this information to be transmitted to IT for evaluation.


What are the advantages of ASi-5 Safety over ASi-3 Safety?

This can save considerable costs in applications with multiple signals. ASi-3 Safety can also be used for modules that have many signals. In this case, however, each safe signal occupies a separate address. Just as with ASi-5, ASi-5 Safety can process much more data per master and thus greatly reduce connection costs – thanks to the significantly higher data bandwidth per address. For example, with the ASi-5 Safety module BWU4210, a total of 2x2-channel safe inputs and an additional 12 I/Os are available under just one ASi-5 address. In contrast, the same amount of data occupies 2 single and 3 A/B addresses with ASi-3.

However, ASi-5 may not always be the most advantageous one. Even with ASi-3 Safety, only one address is occupied for a single E-stop with a 2-channel safe input – and at lower cost. Both technologies will therefore be used in parallel in the future.


What should be taken into account when using ASi-5 Safety modules? Can ASi-3 Safety and ASi-5 Safety be combined?

ASi-5 and ASi-3 operate independently and in parallel on the same two-conductor cable with the same electromechanics. Only one gateway with a combined ASi-5/ASi-3 master is required when using both protocols in one installation. The same applies to ASi-5 Safety and ASi-3 Safety – all that is needed is a gateway with a combined master and a combined ASi-5/ASi-3 safety monitor. In the simplest case, it is therefore possible to just replace the gateway in an existing system with ASi-3 Safety. The system can then continue to operate without changes, and ASi-5 Safety modules can be easily added if necessary.

Questions about ASi cable


What is an ASi cable?

The ASi cable is an unshielded, 2-core cable. It not only transmits data and power, but also enables easy and cost-effective installation. Thanks to piercing technology, participants can easily be installed on the profiled (thus reverse polarity protected) ASi cable – with perfect contacting and achieving protection class IP67. An additional 24 V supply is possible without problems.


How is the ASi cable assembled on sensors and actuators?

The sensors or actuators are usually connected by means of piercing technology. In this process, the insulation of the flat cable, which is profiled to protect against reverse polarity, is pierced during installation by two piercing pins without the cable needing to be prepared beforehand. In this way, nodes can be relocated or added directly on the cable at any time without major installation effort.


How can I strip the ASi cable?

An ASi wire stripper is used for stripping ASi cables with an outer insulation of thermoplastic elastomer (TPE) or polyurethane (PUR).


What is an ASi end cap?

ASi end caps are used to protect the bare ends of the ASi or AUX profile cable against dust and humidity up to max. IP67 – for interference-free communication in the ASi circuit. They are available as left and right versions. Many Bihl+Wiedemann nodes and active distributors do not generally require the use of end caps because the cable ends can be terminated in the base.


How long can the ASi cable be and how do you extend the ASi cable?

The total length of the ASi standard network is limited to 200 m for ASi-5 and 100 m for ASi-3. When determining the total length, all junctions must be included in the calculation. For example, with a combination of ASi repeaters and bus terminations, the maximum achievable distance between two slaves in an ASi-3 network is 1,000 m, if the master is appropriately positioned. No more than 2 repeaters (max. 2 connected in series) may be set between a slave and the master.

What is the ASi cable specification?

The ASi cable is specified in the ASi standard (IEC 62026-2 or DIN EN 62026-2).


Which ASi profile cables are suitable for use in drag chains?

The ASi profile cables BW1979 and BW1980 are suitable for drag chains. The installation instructions of the cable manufacturers must be observed, e.g., no upright installation in the drag chain.

Questions about IO-Link


Which components does IO-Link need?

The open IO-Link interface requires only a simple standard industrial cable. Intelligent sensors and actuators can be connected in a cost-efficient manner on an unshielded three- or five-wire cable. For point-to-point communication, each IO-Link device needs an IO-Link master.


What is the function of the IO-Link master?

The IO-Link master handles the communication to the intelligent sensors and actuators. It enables parameterization, diagnostics and access to the cyclic data by means of a connection to the control system.


What are the advantages of IO-Link?

Reduced machine-related costs

A cost-efficient standard cable establishes a connection up to 20 meters long between the IO-Link master and IO-Link device.

High machine availability

Downtimes are reduced because when a defective IO-Link device is replaced, its parameters are automatically transferred to the new sensor by the IO-Link master or control system.

Efficient operation

IO-Link devices can be positioned in the machine directly at the work site. These do not have to be accessible for parameterization.

Demand-oriented maintenance

Continuous diagnostic data of the entire process lengthen maintenance intervals, since systems and machines need to be maintained much less frequently due to the automatic readjustment via IO-Link.


Is IO-Link another fieldbus?

No. IO-Link is a point-to-point connection between an IO-Link master and an IO-Link device (sensor or actuator). The connection's cable length can be up to 20 meters.


Where is IO-Link used?

IO-Link is mainly used in industrial production automation for communication with sensors and actuators.


IIs it possible to retrofit IO-Link in existing systems?

It is possible to extend existing bus systems. As a prerequisite, the system mapping of IO-Link for the respective bus system must be already implemented. It is particularly easy to use IO-Link in conjunction with the ASi intelligent wiring system. Thanks to piercing technology, corresponding IO-Link masters can be easily retrofitted where they are needed.

Questions about passive safety


What dangers arise if modules/ASi circuits have no passive safety?

Without passive safety, one cannot assume that safe switch-off/disconnection of AUX on a standard I/O module will result in a safe state (I/Os de-energized), as this is not guaranteed. The module continues to draw energy via AS-i, and in the event of a fault, the energy might be fed back via AS-i into the AUX network, which is safely switched off.

Thus, the safety achieved by the safe switch-off cannot be guaranteed in the event of a fault. Furthermore, it can lead to unplanned downtimes and increased effort in system planning, installation and commissioning.


According to which standard specification does Bihl+Wiedemann treat passive safety? When is passive safety applicable?

Safe switch-off (passive safety) is standardized by the Machinery Directives 2006/42/EC, EN ISO 13849-1 and EN 62061.


When is passive safety applicable?

Passive Sicherheit ist dann anwendbar, wenn der sichere Zustand der Anlagenteile der Maschine, die durch die passive Sicherheit ausgerüstet werden sollen, durch stromlos Schalten erreicht werden kann (Wirkstromprinzip). Passive safety is applicable when the safe state of the machine's plant components, which are to be provided with passive safety, can be achieved by de-energizing them (active current principle).


Which components in the ASi circuit must be passively safe to take advantage of the safe switch-off principle?

All components that have a connection to different supply potentials and are in the path of a machine's safe switch-off must be passively safe.


What should be considered when replacing a product with a new, passively safe product?

Unfortunately, in order to use such products to add passive safety in a machine that was not previously safeguarded by passive safety, it is not enough to just replace the modules. In this case, a new safety assessment must be carried out on the machine.


How can I determine if a module is passively safe?

This information can be found in our data sheets under the "Environment" category.

Questions about 30 V power supplies


Why are the 30 V power supplies optimally suited for ASi-5/ASi-3 Gateways?

Because we have optimized all new power supplies in endurance tests for use with our ASi-5/ASi-3 Gateways. Interference, which is common in power supplies, is reduced to a minimum in areas relevant to ASi-5.


Are the previous Bihl+Wiedemann ASi power supplies still available?

Yes, the previous power supplies – whether 30 V* or ASi – are still available. If a faulty device needs to be replaced, it is recommended to use a replacement device that has the same item number. When designing a new system or refurbishing an existing machine, it is recommended to use the new 30 V power supplies in combination with ASi-5/ASi-3 Gateways.


* With the exception of BW1927, we are happy to offer model BW4220 as an alternative.


Do the new 30 V power supplies also work with "pure" ASi-3 Gateways?

Yes, the new power supplies also work very well with classic ASi-3 Gateways. However, only under one condition: in the technical data of the gateway, there must be a "Yes" for the criterion "1 Power Supply, 1 GW for 2 ASi circuits" (see, e.g. BWU2546). For all other ASi-3 Gateways and ASi-3 repeaters the ASi power supplies are of course still available.


What is the voltage between ASi+ and PE or between ASi and PE for the ASI-5/ASi-3 Gateways and the new 30 V power supplies?

If FE is connected to the ASi-5/ASi-3 Gateway (functional earth) of the system earthing, there is +15 V between ASi+ and the system earthing and -15 V between ASi- and system earthing. The new power supplies output a differential voltage of 30 VDC. The balancing with respect to FE – together with the decoupling of the communication from the power supply – is realized in the ASi-5/ASi-3 Gateway.


Is it possible to supply several ASi Gateways with just one 30 V power supply?

Yes, the new 30-V power supplies each provide a maximum output current that can be distributed between multiple gateways with decoupling. For example, a possible combination is the operation of two ASi Gateways with two circuits, each with 4 A decoupling in parallel and a 16 A power supply.


Why do I need special power supplies for ASi?

Since ASi transmits power and data simultaneously via the yellow cable, the DC power supply must be decoupled from the AC communication. In the past, this was implemented in a special ASi power supply. Bihl+Wiedemann has integrated this data decoupling in all current gateways, so that all devices can now be operated with ordinary 24 V power supplies. However, there are limitations related to maximum cable length and performance. To ensure efficient supply to the participants, as well as use of the full cable length, we recommend our new range of power supplies. This is also optimized for ASi-3 and ASi-5 communication.

Questions about the ASi-5/ASi-3 Addressing Device


Does the new ASi-5/ASi-3 addressing device replace previous ASi addressing devices?

Yes, because you can easily address ASi modules of all generations using the ASi-5/ASi-3 addressing device. You will also profit from its modern product features: an OLED color display, a powerful energy storage device (supercapacitor) and simple PC connection via a standard USB-C port.


Is it possible to commission different ASi modules with the ASi-5/ASi-3 addressing device?

Yes, we supply the respective ASi addressing cable as an accessory. Find out more about our wide range of ASi addressing cables here.


Is it necessary to have an ASi-5/ASi-3 addressing device for commissioning?

No, you can also commission all ASi modules using just the Bihl+Wiedemann software suite or directly at the gateway. However, the addressing device may simplify the commissioning of an ASi circuit. It enables you to quickly and easily assign an address to the bus nodes without the need for a real bus structure. Commissioning is then performed automatically by the software, if the ASi bus is connected to the PC software via a gateway.

Questions about 48 V Drive Solutions


Which ASi-5 motor modules for 48 V drives does Bihl+Wiedemann currently offer?

To start with, there is the ASi-5 motor module for Interroll EC5000 AI (BWU4212) for efficient control of 48 V motors. Products from other manufacturers and drives can also be controlled with relevant ASi solutions from Bihl+Wiedemann on request. Integration is also possible in "Logistics 4.0" using the new ASi-5/ASi-3 gateways for fieldbuses such as PROFINET, EtherNet/IP, Sercos or EtherCAT.


How extensive is the configuration effort for our 48 V drive solutions?

Compared to other multi-zone controls for conveyor applications, the ASi-5 motor modules from Bihl+Wiedemann and the ASIMON360 configuration software significantly reduce the configuration effort. Settings and parameters are only assigned for the first motor module. These can then be easily copied to all additional modules. The entire system requires only one IP address and only one Web server — the Bihl+Wiedemann system can be put into operation quickly and easily.


To what extent does ASIMON360 fulfill a bridging function of the eCAD and TIA worlds?

ASIMON360 supports consistent, harmonized labeling and identification of equipment within drive systems from the electrical designer's eCAD system to PLC programming portals such as Siemens' TiA (Totally Integrated Automation). To do this, the electrical planner can download an EPLAN macro from the Bihl+Wiedemann website, add the desired devices and carry out the wiring for ASi, auxiliary power, I/O signals and parameters.


What must be taken into account during connection?

Devices with 24 VDC voltage, the ASi connection of devices and the ASi gateway must never be connected to 48 VDC. Therefore, it is advisable to use the designated gray cable.

Questions about Single Pair Ethernet


Is the SPE cable shielded?

Users have a choice: Shielded/unshielded options are available for each SPE standard. However, these cable variants are not necessarily mentioned in the specifications. Depending on the standard, which in turn determines the speed, the cable length can be significantly increased by using a shielded SPE cable. For example, from 15 m (unshielded) to 40 m (shielded) at 1 Gbit/s as defined by 1000BASE-T1 or IEEE 802.3bp.


How resilient is SPE to external influences such as EMC?

The SPE System Alliance consortium makes the following statement on its homepage (singlepairethernet.com): "A complete 360° enclosed stainless steel sheath surrounding the entire connector [SPE] provides excellent electromagnetic compatibility (EMC)." It can therefore be assumed that SPE is EMC-resistant in the industrial environment, especially with the connector and cable shielding mentioned above. Due to the current stage of development, no further details are available.


Does the wiring of SPE differ from conventional Ethernet?

SPE uses the so-called multidrop method, which does not exist in conventional Ethernet. This means that the reach is shorter with SPE, but also that only simple T-pieces without switches are required. Moreover, the cables and connectors are significantly smaller with SPE.


Can PROFINET be simply routed via SPE? What exactly is required for this?

Since PROFINET is an Ethernet-based protocol, it can basically be transmitted via SPE. SPE is just a new physical layer, i.e., new hardware for the transfer of information from protocols such as Ethernet.


The different physical layers are connected via a switch to enable them to communicate with each other.


Can SPE multidrop be implemented with a simple T-piece or does it require a switch in the T-piece?

A simple T-piece is sufficient for SPE multidrop.


How is the data rate affected with SPE when the 1 Gbit/s standard meets the 10 Mbit/s standard?

Due to the current stage of development, no precise details have been published to date. However, it can be assumed that the wiring in such an application scenario is based on the implementation using conventional Ethernet.


It would make sense to connect a switch with 32 ports, each with the data rate of 10 Mbit/s, to a control system via a 1 Gbit/s port. This is the only way to ensure that every port can use the full bandwidth at all times. Most SPE applications in the field could be a combination of switches and point-to-point connections. The point-to-point connections, each limited to 1,000 m in length, would connect the attached sensors to the switch.


Why can SPE and ASi-5 replace classic Ethernet solutions in the field?

SPE and ASi-5 both offer a lean, lightweight, yet powerful infrastructure. As a result, they make Ethernet in the field superfluous in many aspects. At the same time, SPE and ASi-5 make it easier for the industry to digitize the field level – and thus take the step towards IIoT.

Questions about the self-configuring I/O modules


How can I turn off the feedback of a set output?

Each channel can be individually parameterized from the advanced settings of the module. The feedback is switched off by selecting "output only".


What does self-configuring mean?

Self-configuring means that there is no need for signal parameterization. A connected sensor signal is automatically transmitted as digital input. If an output bit is set in the control system, the signal switches to "high". Optionally, the ASi-5 I/O modules can be manually configured. This way, each signal can be used individually as "input only" or "output only".


The output signal requires a 500 mA supply at 24 VDC: Can the device still be connected?

In this case, two signals are required, which are connected together externally via the wiring. If the output bits of the signals are set simultaneously, the maximum current consumption increases proportionally.


How can I prevent a sensor signal from being energized in the wrong direction?

In the factory default settings, any signal can be used as output or input. Setting an output bit has no effect if "input only" has been configured in the advanced settings for this signal.


How can I change the parameter settings for the 4 I/O module?

Since BWU4727 is an ASi-3 module, no channel-specific parameterization can be performed. If an output is set, the signal is an output; if the signal is read, it is an input.


Can the outputs be switched off using passive safety?

Yes, the modules are compliant with passive safety. The outputs are safely shut off by safely switching off AUX externally. Diagnostics are still available via ASi.

Questions about ASi PROFINET Gateways


How do you integrate a Bihl+Wiedemann ASi Master with integrated safety monitor into the Siemens control system?

This video uses a simple configuration as an example to show you how to set up an ASi-5/ASi-3 PROFINET gateway in ASIMON360 and integrate it into the Siemens control system. The video tutorial also includes a quick start guide as PDF.


How do you integrate a Bihl+Wiedemann ASi Master with integrated safety monitor into the Siemens control system?

This video uses a simple configuration as an example to show you how to set up an ASi-5/ASi-3 PROFINET gateway with integrated safety monitors in ASIMON360 and integrate it into the Siemens control system. The video tutorial also includes a quick start guide as PDF.


If you have been using an ASi Master from another manufacturer, what steps are necessary to replace it with an ASi Master by Bihl+Wiedemann?


To exchange the ASi Master, you only have to add a new GSDML file. The device description file can be downloaded from our website and be integrated into the control system. This transfers all necessary data to the control system, thus enabling easy integration of the ASi Master and naming of the data to be transferred.

Learn how to exchange a gateway in the TIA Portal with a successor model or another device in simple steps with this video and the corresponding quick start guide as PDF.

Our Technical Support can be reached at:

Phone: +49 621 33996-0

Fax: +49 621 3392239

E-Mail: supportbihl-wiedemann.de