Microchip logo
  • All
  • Products
  • Documents
  • Applications Notes

8-Bit MCUs

Event System (EVSYS)

What is the Event System?

The Event System lets you connect the on-chip peripherals of an AVR® microcontroller (MCU) without writing any code. This connection enables the peripherals to communicate with each other without involving the Central Processing Unit (CPU) in many AVR devices. Through the Event System, a change in one peripheral can trigger a reaction from a different peripheral – thus enabling the MCU to handle complex control tasks without the need for interrupt service routines. Because of this, AVR MCUs can handle real-time control tasks with low latency and a high level of determinism.

How does the Event System increase system responsiveness?

Almost all embedded designs take advantage of the many peripherals available on modern MCUs. In order to maximize system effectiveness, designers often route data from one peripheral to another using the CPU as an “event handler”. This software-based peripheral-to-peripheral communication can cause issues in many systems due to its lack of responsiveness, reliability and throughput. Typically, a single-core MCU can only handle one event trigger at a time; therefore, developers must decide which peripheral trigger interrupts need to take priority over others. If multiple peripheral triggers require immediate response at the same time, on of the actions will be missed or delayed. However, the Event System’s hardware-based routing network simplifies the handling of these event triggers by providing a direction connection between on-chip peripherals. With the Event System, multiple peripherals can trigger events simultaneously – making any system more responsive, flexible and reliable. The web-based Atmel START graphical configuration tool makes the implementation of these connections quick and easy so that you can spend less time debugging and more time differentiating your end product.

How the Event System Works

  • A change to the state of an event generator (ADC, Timer, I/O Pin, etc.) creates a trigger or “Event”
  • This event gets routed  through the Event System to another peripheral
  • The event user (target peripheral) is then triggered   
EVSYS System Diagram