Interrupt Mechanism

The concept of interrupts was introduced in early computing systems to handle asynchronous events, allowing the CPU to be interrupted and respond to high-priority tasks immediately. This innovation significantly enhanced the efficiency and responsiveness of computers. The first implementations of this concept were in early computer systems in the 1950s. They eliminated unproductive waiting times in query loops and thus improved processor utilization. In the 1960s, mainframe computers from companies such as IBM began to incorporate more advanced interrupt mechanisms that allowed multiple I/O operations to be processed simultaneously. The IBM System/360, introduced in 1964, used interrupts to enable efficient multitasking and real-time processing. 

As real-time processing became increasingly vital across various industries, interrupts played a significant role in industrial control systems, enabling these systems to provide immediate responses to events. In the 1970s, the introduction of Programmable Logic Controllers (PLCs) marked a significant milestone in industrial automation. PLCs utilized interrupts to process external signals in real-time, becoming essential components in manufacturing processes. The decade also saw the development of early industrial communication protocols like Modbus, which integrated interrupt-driven mechanisms to efficiently manage data exchanges. 

The 1980s witnessed further advancements in PLC capabilities, allowing for more sophisticated interrupt handling and enhanced coordination in complex automation systems. This era also introduced protocols such as PROFIBUS, which leveraged interrupts to ensure timely data transmission between devices in automated environments. Ethernet technology began to be adopted in industrial settings during this time, where interrupts were crucial for managing network traffic and ensuring reliable communication. 

The 1990s and 2000s saw significant strides in the standardization and evolution of real-time communication protocols. CAN Bus, introduced by Bosch in 1986, utilized interrupts to achieve real-time communication in automotive and industrial applications. The widespread integration of Ethernet technology into industrial communication systems led to the development of standards such as Ethernet/IP and PROFINET, which utilized interrupts for efficient network communication in the form of efficient and deterministic data exchange. The need for faster and more reliable communication continued to drive the development of protocols like EtherCAT and SERCOS III in the 2000s, which used advanced interrupt handling techniques to facilitate high-speed, low-latency data transfers. 

Hence, the history of interrupts in industrial communication has seen a significant evolution from basic hardware mechanisms to the sophisticated real-time control systems essential for modern automation technology and the industry 4.0 landscape. This progression reflects an integration of increasingly advanced technologies and their impact on both computing and industrial processes. 

Interrupts are essential mechanisms in both hardware and software systems that signal the processor to immediately address a high-priority event. When an interrupt occurs, the processor halts its ongoing operations, saves its state, and executes a specialized function known as an Interrupt Service Routine (ISR). The primary purpose of an ISR is to handle the specific event or condition that triggered the interrupt. After the ISR performs the necessary actions, the processor resumes its previous tasks. Hence, interrupts are pivotal for managing real-time events and facilitating efficient communication. They handle signals from sensors, communication interfaces, and control commands that demand instant processing. The exemplary mechanism of an interrupt event is as shown below. 

The interrupt mechanism solves multiple problems in industrial systems, including: 

1. Inefficiency and Resource Wastage 

Before interrupts, industrial systems used polling, where the CPU continuously checks each device or sensor in a sequence, consuming considerable processing power even when there was no new data. This method caused high latency as the CPU had to cycle through all devices, potentially missing critical updates. 

Interrupts address this by allowing the CPU to remain idle or perform other tasks until an event occurs, thus saving processing resources. The immediate handling of high-priority events significantly reduces the response and latency time. 

2. Lack of Real-time Responsiveness 

Polling could not guarantee real-time responsiveness, which is crucial for applications such as process control or robot movements. Interrupts provide a remedy here by enabling an immediate response. The system can react immediately to critical events, ensuring that time-critical processes are executed without delay. 

3. Scalability Issues 

As the number of devices or sensors increased, the overhead and complexity of polling each device increased, making systems less scalable and more difficult to manage. Interrupts provide a remedy here, as the devices signal the CPU independently and directly when they need attention. This simplifies system management and supports scalability 

4. Unpredictability in Timing 

Polling could not guarantee predictable scheduling for handling events, resulting in non-deterministic system behavior. Interrupts address this by providing a predictable method for event handling that prioritizes critical tasks for timely processing. 

5. Resource Prioritization 

Polling treats all tasks with the same priority, which is inefficient in industrial systems where some tasks are more urgent than others. Allowing different priority levels for interrupts ensures that more critical tasks are processed first, while less critical ones wait. 

As a market leader Hilscher offers a wide range of products for industrial communication in RTE networks. The netX technology and the multiprotocol-capable SoCs (System on Chips) based on it are at the forefront. These can be integrated into industrial components - such as controllers, sensors or actuators - as highly integrated communication interfaces. Thanks to the associated firmware, which can be loaded onto the chip for the required protocol stack, Hilscher supports component manufacturers and automation specialists in the development of flexible solutions for use in a wide variety of RTE networks – for example for PROFINET, EtherCAT, EtherNet/IP, CC-Link IE or Ethernet POWERLINK. 

Based on the netX communication controllers, Hilscher developed different embedded modules and the PC and fieldbus cards of the cifX family (which are available in all common form factors - from PCI and PCIe to the smallest multiprotocol-capable PC cards on the automation market in M.2 format). These communication interfaces already include the necessary chip peripherals and are therefore faster to integrate. 

In addition, gateways, switches and network and communication diagnostic devices support the smooth operation of fieldbus networks. 

Next to RTE systems, Hilscher's components for industrial communication networks also support the most common fieldbus protocols - such as PROFIBUS, Modbus, CC-Link or DeviceNet. 

The portfolio is rounded off by the netFIELD ecosystem for Managed Industrial IoT. From the edge gateway to the cloud platform for centralised container management, netFIELD offers everything you need to develop modern applications in line with Industry 4.0.