Renesas 70 3.1 Concept of Real-time OS

Chapter 3 Introduction to MR308
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3.1 Concept of Real-time OS
This section explains the basic concept of real-time OS.
3.1.1 Why Real-time OS is Necessary
In line with the recent advances in semiconductor technologies, the single-chip microcomputer ROM capacity
has increased. ROM capacity of 32K bytes.
As such large ROM capacity microcomputers are introduced, their program development is not easily carried
out by conventional methods. Fig.3.1 shows the relationship between the program size and required develop-
ment time (program development difficulty).
This figure is nothing more than a schematic diagram. However, it indicates that the development period in-
creases exponentially with an increase in program size.
For example, the development of four 8K byte programs is easier than the development of one 32K byte pro-
gram.5
Program Size
Kbyte
4816 32
Development Period
Figure 3.1 Relationship between Program Size and Development Period
Under these circumstances, it is necessary to adopt a method by which large-size programs can be developed
within a short period of time. One way to achieve this purpose is to use a large number of microcomputers hav-
ing a small ROM capacity. Figure 3.2 presents an example in which a number of microcomputers are used to
build up an audio equipment system.
5 On condition that the ROM program burning step need not be p erformed.