Acyclic Data Transmission

Acyclic data transmission is a method of transferring information within a network or system in a manner that ensures data flows in a one-way direction without forming loops or cycles. This approach is characterized by a linear progression of data from a source to a destination, without the possibility of the data returning to the source or creating closed loops. In contrast to cyclic communication, which involves regular and periodic data transfers, acyclic communication occurs on demand or in response to specific triggers or events. This approach allows for the transmission of information that is not part of the routine cyclic process, such as configuration data, diagnostic information, or commands that require immediate attention.

It plays a crucial role in facilitating on-demand communication between devices. For instance, in applications like Programmable Logic Controllers (PLCs) and Variable Frequency Drives (VFDs), acyclic communication enables the transfer of critical or time-sensitive data outside of the standard cyclic operations. This flexibility enhances the responsiveness and efficiency of industrial processes by allowing devices to interact beyond their regular cyclic exchanges.

Acyclic communication offers versatility in handling non-routine data transfers, ensuring that essential information can be transmitted promptly when needed. By understanding the distinction between cyclic and acyclic communication, users can optimize data exchange processes in industrial environments, improving system functionality and adaptability to varying operational requirements.

It also facilitates the orderly and efficient movement of information within a network or system by ensuring that data flows in a unidirectional manner without forming loops or cycles. This approach is essential for various applications requiring structured and predictable data flow, ranging from real-time data processing to workflow automation.

Acyclic data transmission offers several advantages in the realm of industrial automation and data exchange, making it a preferred method for specific use cases.

• Flexibility and On-Demand Data Exchange

  Acyclic communication allows for data exchange on an as-needed basis, providing flexibility in transmitting information when specific requests or conditions arise. This flexibility is particularly valuable for tasks that do not require continuous or periodic updates but rely on immediate data transfer.

• Predictable Processing

  With acyclic transmission, data follows a predefined path through various processing or routing stages. This predictability allows for better resource allocation, scheduling, and optimization of processing tasks, resulting in more consistent performance and response times.

• Scalability and Device Interaction

  Acyclic communication is well-suited for scenarios where many devices are present within a network. It facilitates interactions between devices beyond standard cyclic operations, enabling efficient device parameterization, network diagnostics, and on-demand information retrieval across multiple devices. It is very well suited for industrial automation and communication.

• Control Over Data Transfer

  One significant advantage of acyclic communication is the control it offers in terms of data transfer speed and size. Users can manage the speed of data transmission and can send any size of data without concerns about time constraints, providing a high level of control over the communication process.

• Support for Complex Workflows

  Acyclic data transmission is well-suited for managing complex workflows or data pipelines that involve multiple interconnected processing stages. The linear progression of data enables the orchestration of diverse tasks and dependencies in a structured and manageable manner. This feature is very useful in industrial settings.

• Enhanced Network Management

  Acyclic communication can lead to more predictable network loads compared to cyclic communication, making network management easier and more efficient. By varying the priority of data exchanges based on demand, acyclic communication optimizes network performance and resource utilization.

Acyclic data transmission stands out for its flexibility, efficiency in handling non-routine data transfers, control over data transfer parameters, scalability in device interactions, adaptability to diverse applications, and its contribution to enhanced network management in industrial automation settings.

Cyclic and acyclic data transmission represent two different approaches to transferring information within a network or system.

• Scheduled vs. On-Demand

  Cyclic communication involves regular, scheduled data exchange, while acyclic communication is on-demand and does not have a predetermined schedule.

• Data Speed and Size

  Cyclic communication allows for efficient management of data speed and size, as it focuses on time schedules and ensures that data is exchanged on time. Acyclic communication provides more control over data speed and size, as it does not have a predetermined schedule and can transmit any size of data without worrying about time.

• Network Management

  Cyclic communication can lead to predictable network loads and easier network management, as the network load varies based on the demand for data exchange. Acyclic communication can also lead to predictable network loads, but it may result in occasional data collisions and potential neglect or loss of critical data requests.

Acyclic communication is more flexible and is more efficient for systems where data doesn't need constant updating. It is used for non-time-critical data exchange, such as configuration or diagnostic information.

This form of communication is particularly useful in industrial automation and control systems, where it can be used to adjust device parameters, perform diagnostics, or handle configuration changes during runtime. Here are the technical features of acyclic data transmission:

• Device Parameterization and Diagnostics

  Acyclic communication allows for the adjustment of device parameters during runtime. For example, a parameter master in PROFIBUS technology, known as a class 2 master in the corresponding terminology, can establish a connection with a slave device and exchange data acyclically. This is particularly useful for fine-tuning device settings or performing diagnostics without interrupting the cyclic communication that may be handling critical process control data.

• Alarm Handling

  There is an alarm model for Acyclic data transmission; it enables the exchange of alarm and diagnostic information between devices. In this, each slave device has a status machine for alarms. This "alarm channel" allows devices to transmit encoder-specific alarms and warnings according to the relevant device profile. The alarm channel can be enabled or disabled via a configuration parameter, allowing the user to control whether these alarm messages are transmitted. When the alarm channel is enabled, any errors or warnings detected by the device can be communicated to the controller through the acyclic data exchange. For example, PROFIBUS also defines an alarm model for acyclic data exchange. This model checks for various incoming and outgoing alarms and ensures acknowledgment by the class 1 master.

• Error Detection and Correction

  Acyclic data transmission systems incorporate error detection and correction mechanisms to ensure data integrity and reliability. This may involve adding checksums or error-correcting codes to data packets, as well as implementing acknowledgment and retransmission protocols to recover from transmission errors.

• Flexibility in Data Size and Speed

  With acyclic communication, there is significant flexibility in the size and speed of the data transfer. Users can transmit any size of data without worrying about time constraints, and the speed of data transfer can be adjusted according to the requirements of the task at hand. This level of control is not typically available with cyclic communication, where data is exchanged at fixed intervals and often at a predetermined speed.

• Separate Communication Channels

  To handle the different timing and bandwidth requirements, acyclic data is typically transmitted over separate communication channels or "lanes" from cyclic process data. For example, in PROFINET, acyclic data uses the "NRT" (non-real time) communication channel, while cyclic process data uses the "RT" (real-time) channel.

• Data Security and Reliability

  While acyclic communication does not guarantee the exchange of data since no error is generated for missed transfers, it can still be configured to ensure a high level of data security. The flexibility of acyclic communication allows for the transmission of data with varying priorities, where some requests may have higher priority over others, ensuring that critical data is transferred reliably.

Acyclic data transmission is characterized by its on-demand nature, flexibility in data size and speed, efficiency in network management, capability for device parameterization and diagnostics, structured alarm handling, and the potential for high data security and reliability. These technical features make acyclic communication a valuable tool in various industrial automation applications where non-time-critical data needs to be exchanged flexibly and efficiently.

With its broad product portfolio of components for industrial communication - from communication controllers, embedded modules, PC, and fieldbus cards to IO-Link masters - Hilscher supports its customers with both cyclical and acyclical data exchange in production systems. All these components are based on the company's own multi-protocol-capable netX SoCs and the available loadable firmware, which can be used to handle all common fieldbus and Industrial Ethernet protocols.

In addition to the communication interfaces for field devices and controllers, Hilscher also offers gateways, edge gateways, switches, and diagnostic devices as supplementary components for system networking, which also support both types of data transmission.