Highly Integrated 8-bit MCUs Can Help Simplify CAN Automotive Applications

Edwin Romero,  Product Marketing Manager - MCU8 Division, Microchip TechnologyHaving completed his B.S. Electronics Engineering from the Arizona State University, Edwin is a semiconductor industry veteran who has been in the industry for over a decade. Prior to joining Microchip Technology, he headed the Applications & Marketing Communications for Corporate Marketing for On Semiconductor

The controller area network (CAN) protocol is a great way to reduce the wiring complexity in data transmission, as applications become increasingly interconnected. Ever since it was designed in the mid 1980s specifically for the automotive industry, it has helped reduce the weight, amount and cost of wiring.

Today, CAN is used widely in factory automation and medical applications. More than one billion CAN nodes are shipped worldwide each year. If we look at the number for 8-bit microcontroller units(MCUs) too, we find that over one billion are shipped annually. While there might possibly be some overlap in these numbers, the point remains that this number is set to grow exponentially in the future.

Why Car Makers Love CAN
Traditional CAN communications are event based. Through CAN, micro controllers and application specific integrated circuits(ASICS)can directly communicate with each other in applications without a host computer. CAN today is more cost-effective and compatible with many automotive systems, thanks to its integration by semiconductor companies. For more than a decade and half now, 8-bit MCUs are offered with the CAN protocol. More recent 8-bit MCU design approaches use Core Independent Peripherals (CIPs)that allow them to address several system aspects in CAN applications.

While cost effectiveness is a key reason for the success of CAN, features such as robustness, reliable data transmission and the simplicity of its implementation have played a role in its popularity. Most of these attributes are also applicable to 8-bit MCUs. It is not surprising that 8-bit MCUs with CAN are seen as a natural combination especially in automotive networking.

As automotive networks evolved, there arose a need for time triggered, fault tolerant and single wire implementations, as well as CAN with flexible data rate(CAN FD). CAN specifications expanded accordingly. CAN now has several applications in automotive right from access control, battery charging/battery management to use in diagnostic equipment. While automotive engineers have been using the local area network(LIN) protocol to reduce costs, it is not feasible in applications that require access to data from another CAN control system. This is because LIN is a single wire, master slave network that requires both hardware and software changes from CAN.
Therefore, 8-bit MCUs/CAN are better suited for these applications.

An 8-Bit MCU with CAN to Meet LowCost Networking Requirements
Designers seek to simplify tasks such as sensing parameters for control purposes, moving a motor, activating a solenoid and others, through added peripherals that specifically address other system requirements. The CIP approach works very well because it can help improve response times at lower clock speeds and decrease software complexity. At the same time it uses lesser power.

The integrated CAN controller is fully backwards compatible with previous CAN modules such as CAN1.2 and CAN 2.0A. The product comes with Memory Access Partition (MAP)capability that supports designers in data protection and boot loader applications. It also has a Device Information Area(DIA) that provides a dedicated memory space for factory programmed device ID and peripheral calibration values.

CAN today is more cost-effective and compatible with many automotive systems, thanks to its integration by semiconductor companies

8-bit MCUs have played a significant role in improving serial communications, including UART with support for Asynchronous and LIN protocols in addition to higherspeed, standalone I2C and SPI serial communication interfaces.

The CAN plus CIPs combination make 8-bit MCU programming simple and easy. With CIPs,8-bit MCUs work as a great alternative to the more expensive and difficult to program 16-bit MCUs, especially when they provide sufficient processing power for remote nodes.

The onchip hardware modules are highly configurable and handle repetitive embedded tasks more efficiently and deterministically. For example, CIPs can still continue operations outside of the core in instances where an MCU gets caught in a loop.

Network designers today have considerable flexibility and numerous options for implementing CAN and LIN communications. Many of the typical 8-bit MCU LIN applications can be performed with CAN as well. This is true in instances where the module needs to be aware of other data on the network, such as for windshield wipers that can change their speed based on the vehicle’s speed. Another application is multicolor LED mood lighting in vehicles. For years, this was done using PWM and complementary waveform generator CIPs with the drivers connected to a LIN bus because the MCUs did not have CAN. A cost effective 8-bit MCU with CAN could provide flexibility and a simplified alternate approach to the design. System level CIPs often eliminate the need for an additional ASIC or two.

Most 8-bit MCUs rely heavily on the core for processing its peripheral’s functions. CIPs perform several system design possibilities such as precision interface to various sensors highpower LED driver and/or a reasonably complex level of motor control, without significantly taxing the CPU.

A variety of development tools are available to determine the possibilities for a specific network. The MPLAB Code Configurator(MCC) is a great example of a free software plug-in that provides a graphical interface to configure peripherals and functions specific to the application. It allows system design engineers to easily configure hardware based peripherals without the need to write and validate an entire software routine, to accomplish a specific task.

A CAN-Do Attitude
System designers use various types of bus architectures for automotive and industrial applications. When additional sensing and/or control are required for an existing network, an MCU with CAN is a great choice. With its Core Independent Peripherals, the 8-bit MCU/CAN family allows CAN expansion into more cost sensitive nodes on the network.

Whether you require a flexible, cost-effective, simple and reliable robust data transmission or an increased performance and system support for access control battery charging/battery management and diagnostic equipment the new 8-bit MCU/CAN+CIPs that address emerging automotive network applications are the solution.