Microcontrollers may be classified into those for control applications and those for embedded applications. How do these microcontrollers differ from "ordinary" microcontrollers? A microcontroller is used inside a system, such as an automobile, PC, air conditioner, video recorder, mobile telephone, TV, or electronic rice cooker (in other words, it is used embedded into a system). Practically the only people who carefully look at microcontrollers are those who actually make them and hobbyists.
Microcontrollers for control or embedded applications have functions reinforced for embedded applications or are especially designed to be easy to use with such applications.
Microcomputers can be classified into microprocessors called MPU or CPU and microcontrollers called MCU.
<Reference: Early microcontrollers>
The very first and famous microcontroller, the 8080, was called a CPU, and the 6800 was called an MPU. CPU stands for Central Processing Unit, which emphasizes the part that plays a central role in a computer. A system that consists of two or more LSIs and performs the same processing is also called a CPU. On the other hand, the name MPU stands for Micro Processing Unit, and emphasizes that one LSI constitutes a unit. Today, functions other than a CPU are integrated on a single LSI, there is therefore no distinction between a CPU and a MPU. |
Data is input into a computer that processes (calculates) the data and outputs the result. A microprocessor is intended to process the data and therefore consists mainly of CPU functions. Examples of functions that constitute a computer are shown below. Recent microprocessors integrate not only CPU functions but also functions gathered at the center and surrounded by a dark cream color. Some have even functions surrounded by a light cream color, such as ports, and A/D and D/A converters. Many microprocessors, however, require the connection of an external ROM that stores instructions.
<Reference 2: Microcontroller's usage for data processing>
The range of applications of microcontrollers is viewed from the point of data processing capability as follows.
The basic size of data that a microcontroller can handle is 4 bits. Because 4 bits handle the statuses of 0 to 15, the microcontroller mainly handles numerals. As the application field, therefore, a cache register that mainly calculates decimal numbers can be cited.
Because the statuses of 0 to 255 can be handled by 8 bits, an 8-bit microcontroller can use characters such as alphabetic characters, in addition to numerals. Because characters can be used, the application of the microcontroller covers English word processors and personal computers.
If 16-bit data can be handled, two-byte characters can also be used. A 16-bit microcontroller can therefore support Japanese. However, a 16-bit microcontroller is not sufficient for handling data such as sounds and images.
A 32-bit microcontroller can handle sounds and images because much larger data can be handled. |
A microcontroller (MCU) has an internal ROM, so it can operate even with a single LSI by writing instructions to this internal ROM, thus allowing a more compact system to be organized.
<Reference 2>, above, introduces applications for data processing of microcontrollers when microcontrollers are classified by their number of bits. In the following discussion, the differences between these applications and applications for control and embedded systems are described.
In a "control application", necessary processing is performed on an input signal and the result is output. Unlike in "data processing application", the input signal comes from the status of a switch or a sensor that converts physical information such as temperature and magnetism (analog variable). In accordance with the input signal, a microcontroller for a control application performs processing such as to illuminate a light when a switch is pressed and sound an alarm if a temperature exceeds a specific value.
Information of a switch is usually 1 bit. This means that a microcontroller for a control application must be able to process 1-bit information efficiently. Because physical quantities in the natural world are analog variables, the output signals of a sensor are analog signals. An A/D converter is necessary to use these signals. Some of the output signals of a microcontroller for control applications are 1-bit to perform an ON/OFF control action such as to illuminate or extinguish a light, some are analog signals that control brightness, issue sounds, or control DC motor, while the others are signals that drive an actuator such as a motor or, in some cases, a display unit such as an LCD or fluorescent indicator panel. Microcontrollers are therefore required to have output functions for supporting these signals.
To use a microcontroller in a mobile system, it is necessary that the system be organized to be compact. In addition, low-voltage operations and low power consumption are important factors.
Microcontrollers for control or embedded applications therefore have functions suitable for various purposes, by providing particular features.
SITE MAP
