- Advantages of AS-i
- System overview
- AS-i vs. IO-Link
Compare two industrial communications: AS-i vs. IO-Link
AS-i (AS-Interface) and IO-Link are industrial communication standards designed to connect sensors and actuators to control systems. However, they take fundamentally different approaches to data transmission and device management:
- AS-i excels as a simple, cost-effective bus system for connecting basic digital I/O devices across multiple points
- IO-Link provides intelligent point-to-point communication with advanced diagnostics and parameterization capabilities.
This guide compares and contrasts the two technologies in terms of implementation, applications, technical specifications, and more.
More reading: What is an AS-i network? | IO-Link: An introduction
When to use AS-i or IO-Link
Choosing between AS-i and IO-Link depends largely on whether an application prioritizes simplicity and cost (AS-i) or intelligent data exchange and device management (IO-Link). The two technologies also work well together in certain applications.
Choose AS-i for:
- Simple digital I/O applications
- Cost-sensitive projects
- Basic conveyor and material handling systems
- Safety-related applications requiring discrete signals
- Applications where multiple simple devices need connection
- Projects prioritizing quick installation and low complexity
Choose IO-Link for:
- Applications requiring device diagnostics and monitoring
- Intelligent sensor integration
- Process optimization through data analysis
- IIoT and smart factory implementations
- Applications needing remote device parameterization
- Systems where device data beyond simple on/off states is valuable
Using AS-i and IO-Link together
In the right situations, AS-i provides a cost-effective backbone infrastructure while IO-Link delivers intelligent device communication. An integrated system maximizes operational efficiency and economic value.
- The AS-i bus cable allows for low wiring complexity. AS-i's bus topology eliminates complex point-to-point wiring by connecting multiple devices to a single two-wire cable.
- Easy acquisition of digital sensor data. AS-i collects discrete digital signals from sensors and actuators across the network, providing reliable on/off status information with minimal configuration requirements.
- IO-Link offers digital process value transmission. IO-Link transmits rich process data including measurements, diagnostics, and device status information, enabling data-driven decision making.
- Sensor parameters are set via the standardized IO-Link interface. Remote parameterization through IO-Link eliminates manual device configuration, allowing automatic parameter downloads and device replacements without field visits.
- Integration of IO-Link into AS-i systems is possible. IO-Link devices can connect to AS-i networks through specialized gateways, although this integration operates at reduced speeds compared to direct IO-Link connections.
- Gradual migration strategies reduce implementation risk and cost. Organizations can start with AS-i infrastructure and systematically add IO-Link capabilities as requirements evolve.
- IO-Link devices can serve as intelligent feeders for AS-i networks. Smart sensors with IO-Link interfaces can process data locally before feeding relevant information into the AS-i bus.
AS-i and IO-Link: Technical Specifications
AS-i
- Network Speed: 167 kbps
- Cable Length: Up to 100m (Up to 300m with repeaters)
- Device Capacity: 62 slaves per segment
- Power: 24V DC via the same cable as data
- Data per Device: 4 bits input, 4 bits output
IO-Link
- Communication Speed: 4.8 kbps, 38.4 kbps, 230.4 kbps
- Cable Length: Up to 20m (Up to 240m with repeaters)
- Connection: Point-to-point
- Power: 24V DC via 3-wire connection
- Data Volume: Up to 32 bytes per cycle
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| Supports 2-wire (power and communication) |  |
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| Extremely long trunk cable runs | |
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| Standard cabling to sensor | |
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| High EMC immunity | |
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| Access to sensor parameters and settings | |
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| Detailed sensor diagnostics | |
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| Non-proprietary | |
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| Supports high amperage solenoid outputs | |
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| Supports native inclusion of the other | |
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| Supports standard and IP69K washdown applications | |
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AS-i vs. IO-Link: Key differences at a glance
| AS-i | IO-Link | |
|---|---|---|
| Architecture | Bus topology | Point-to-point |
| Communication type | Discrete digital I/O (4 bits per device) | Bidirectional: I/O, parameters, diagnostics |
| Wiring | 2-wire (power + communication), long cable runs, high EMC immunity | Standard 3-wire sensor cables |
| Cost & complexity | Simple and cost-effective | Higher cost, more intellige |
| Device intelligence | Connects basic digital devices | Supports smart devices with embedded intelligence |
| Data capabilities | Basic signals only | Process data, parameters, diagnostics, device ID |
| Device management | Manual addressing | Automatic identification, parameterization, easy replacement |
| Diagnostics | Limited fault detection | Detailed diagnostics, predictive maintenance |
| IIoT integration | Minimal smart factory readiness | Strong IIoT foundation |
| Installation time | Fast setup with bus structure | Quick configuration and device swap |
| Scalability | Up to 62 devices per network segment | Up to 8 devices per master and unlimited masters per network segment |
| Data volume | Low (4 bits per device) | High (process + configuration data) |
| Typical applications | Conveyor control, safety systems, simple automation | Intelligent sensing, condition monitoring, flexible automation |
| Environmental support | Supports IP69K, washdown, high current outputs | Supports IP69K, washdown, sensor-level parameter access |
| Standards compliance | Non-proprietary, interoperable | Non-proprietary, interoperable |
| Data volume | Low data volume (4 bits per device) | High data volume with parameter sets |
| Maintenance | Basic fault detection | Predictive maintenance capabilities with continuous monitoring |