Five Steps to Make Your New Product Design Functionally Safe

Government regulations require that many new electronic products comply with international functional safety standards. For example, IEC 61508 is the applicable safety standard for industrial products. It is the basis for several other safety standards, such as ISO 26262 for automotive systems and IEC 60730 for home appliances and white goods. Failure to comply with these standards can seriously affect your company and its product users. In this blog post, we outline five steps to help you plan for functional safety in your new product designs.

1. Select a Microcontroller (MCU) With Built-in Safety Features

The AVR^® DB and AVR DD MCUs are the most recent additions to Microchip’s 8-bit AVR family. These devices have built-in safety functions to help detect and respond to voltage supply variations or drops. They also offer Core Independent Peripherals (CIPs) and a hardware-based Event System that enables inter-peripheral communication without CPU involvement, thus reducing latency and ensuring faster system response. This helps to reduce the amount of software that you need to develop and validate, which in turn reduces design risk. These MCUs provide all the features that you need to create safety-critical applications which are reliable and robust.

2. Make Use of Advanced Peripherals

Your next step should be to familiarize yourself and learn how to implement the various peripheral functions that these MCUs provide. These features, which you can use to design safety-critical features into your product, include:

• Power-on Reset (POR)
• Brown-out Detector (BOD)
• Voltage Level Monitor (VLM)
• Windowed Watchdog Timer (WWDT)
• Cyclic Redundancy Check (CRC)
• Clock Failure Detector (CFD)
• Fault detection using Event System

3. Select the Right Software Development Tools

With your hardware sorted, next, you must ensure you have the right software. To simplify the software verification process, we provide a Class B Functional Safety Library for AVR MCUs that provides the necessary self-test modules to implement software safety requirements to comply with the IEC 60730 Class B standard. The library includes software routines for the WDT, BOD and other functions described in AN2632: Guide to IEC 60730 Class B Compliance with tinyAVR^® 1-Series. The Class B Library can also be used as the starting point for designing a product to comply with any other functional safety standard.

4. Protect Against Environmental Hazards

Electrostatic Discharge (ESD) and Electromagnetic Interference (EMI) can seriously harm or even destroy an electronic system. You must ensure your printed circuit board and hardware are adequately designed to protect against electrical and magnetic phenomena in your end product.

5. Test Your Design

The final step is to test your product and evaluate the level of safety it provides. Our AVR Functional Safety Field Engagement Board (ATAVRFEB-SAFETY), based on an ATtiny3217 MCU, provides an all-in-one platform to demonstrate and evaluate the safety and reliability features available on PIC^® and AVR devices. At the center of the board, the “Application Heartbeat” indicator shows whether the application is running correctly or not. An accelerated heartbeat indicates a problem has been detected, and a status LED lights up to reveal the cause of failure. The board has five main sections that include status LEDs for user feedback. It is powered by a 5.0V USB cable and consists of an onboard Mini Embedded Debugger (mEDBG) that can be used to program and debug the ATtiny3217 MCU. The drivers for the board are available in Atmel Studio 7, and the example code can be downloaded from Atmel START. This intuitive, web-based configurator tool makes it easy to get started with your application development.

Figure 1 AVR^® Functional Safety Field Engagement Board

Reinforcing Functional Safety

You can learn more about the many features and testing capabilities of the AVR Functional Safety Field Engagement Board in the AVR Functional Safety Hardware User’s Guide and AN2541: Functional Safety Demonstrator Using ATtiny3217. For additional information about the safety and monitoring features available on these MCUs, visit our ATtiny3217 product family page. You can purchase the AVR Functional Safety Field Engagement Board from microchipDIRECT or our worldwide distribution network.