Part 3 ― Advanced Solutions for Vehicle Control Applications

The Renesas Approach to Vehicle Control: Body Control Solutions

Body control systems are used to implement features such as the power windows and electrically operated sliding doors that help make vehicles more comfortable and pleasant. They support the business objective of "building cars that are kind to people." The broad span of compatible Renesas microcomputers in the M16C family satisfy the diverse design requirements of body control applications, many of which involve controlling various types of electric motors. Our M16C microcomputers are also built into ECUs and network gateways and other automotive applications.

Body control systems in cars comprise numerous different applications: doors and windows, sunroofs, windshield wipers, seats, air conditioning, and movable headlights, among others. The electrically operated mechanisms in these applications have dramatically expanded and enhanced the vehicle comfort and convenience features that car makers use to differentiate the models they offer. In most cases, microcomputers direct the actions of the multiple types of electric motors that power those features. Design requirements vary tremendously, and the microcomputers selected to implement the features vary accordingly. To minimize development costs, it's best if the microcomputers used in a vehicle are compatible members of the same product family.

One characteristic of body control systems is that people can see or touch them. For instance, drivers and passengers are directly aware of the movement of doors and other parts. This leads to a requirement for particularly delicate control methods that often incorporate safety features, such those that as prevent people from getting caught in and harmed by the mechanisms. Another characteristic of these systems is that their specifications can change often. For example, modifications might be made to the speed at which doors or windows open and close. A third characteristic is that the features provided by body control systems add value to an automobile and can convey a perception of superior quality. The broad and changeable requirements of the various body control systems mandate that the microcomputers used in them be flexible and be supported by easy-to-use and efficient hardware/software development tools.

The Renesas M16C family meets those mandates and more. It encompasses an extensive range of software- compatible and pin-compatible microcomputers that are popular solutions for body control functions and other automotive applications such as ECUs and network gateways. Sharing a common platform, these cost-effective devices deliver the wide span of optimized combinations of peripherals and performance necessary for meeting diverse design requirements. They generate low levels of noise and have a high tolerance for external noise. They are power efficient, too, making them suitable for situations in which power supplies are limited and there isn't much space to install circuit boards.

The pin compatibility provided between M16C devices helps to simplify circuit board designs and facilitate design upgrades, while the software compatibility maintained within the product line makes it easy to reuse existing software, saving engineering resources and shortening development times. Additionally, the microcomputers in the M16C family include have numerous built-in peripheral functions that save cost by reducing the number of external components required for system designs. Importantly, those peripherals include multi-function timers and other internal functions that are suitable for motor control applications and have been well proven in home appliances. Moreover, the reliability that Renesas M16C devices have demonstrated in appliances and technical know-how we have acquired in serving that fast-paced market are important strengths valued by the customers in automotive markets.

Because virtually all of the requirements of all body control systems can be met by microcomputers in the M16C family, automotive engineers can standardize on this versatile architecture. They can use microcomputers in the R8C/Tiny series and M16C/Tiny series for sub-ECUs and systems requiring motor control functions, for instance. Additionally, they can use devices in the R32C/100 series for ECUs that perform centralized control of various operations (see Figures 1 and 2).

The main models in the low-end R8C/Tiny series are the devices in the R8C/20 to 23 product groups (48-pin package), the R8C/26 and 27 groups (32 pins), and the R8C/28 and 29 groups (20 pins). The modern, CISC-type CPU of these 20MHz, 16-bit microcomputers incorporates a 16-bit hardware multiplier to speed math calculations. The devices offer scalability and low cost, and are available in versions with on-chip flash memory sizes from 16Kbytes to 128Kbytes. They provide a 40MHz high-accuracy on-chip oscillator that eliminates the need for external oscillators, reducing system cost. They also have functions for motor control and incorporate multiple fail-safe features.

The main models in the mid-range, 20- or 24MHz M16C/Tiny series of 16-bit microcomputers are the products in the M16C/26T group (48 pins) and the 20M16C/28 and 29 groups (64 and 80 pins). They have a CPU with a 16-bit hardware multiplier and provide a built-in motor control timer. Other available on-chip peripherals include a CAN controller and a hardware multi-master function.

Evolution of the R8C/Tiny series and M16C/Tiny series is ongoing. Currently, we are developing the "R8C/Next" series, devices that will offer more inputs and outputs, still at low cost. We are also working on the "M16C/Next" series devices that will have a faster, higher-performance (32MHz) CPU.

The R32C/100 series of flash microcomputers ― the product line at the top of the M16C family ― is currently under development. Devices in this series have the performance and features necessary to support centralized control applications such as ECUs. They incorporate a high-performance 32-bit CISC CPU with floating point unit (FPU) that runs at fast speeds and have enough on-chip memory for storing large programs. Models with 48MHz, 60MHz, 64MHz, and 80MHz capabilities are planned, and chips with flash memory sizes between 256Kbytes and 1Mbyte are under consideration.

To enable advanced ECU designs, the microcomputers in the R32C/100 series include a number of LAN interfaces that can be used to control other circuits such as microcomputers or logic via an in-vehicle LAN. For example, the devices will include two, three, or four CAN interface channels and from two to eight LIN interface channels. Also, versions are being developed that will support the FlexRay in-vehicle LAN standard, which offers more bandwidth than CAN. Various high-pin count models within the same architecture will be offered, allowing smooth scaling of the number of network I/Os in system designs.

For more information on M16C/Tiny microcomputers, click here

For more information on R32C/100 microcomputers, click here