Requirements of a Microcomputer System

Abstract

In this chapter we discuss the general requirements of a practical system. Figure 5.1 shows a block diagram of a functional microcomputer system. The system lacks only a few components to make it into a practical working system; these components include an address bus driver and a data bus driver, which ensure that the address bus and the data bus, respectively, can deal with the loads connected to them. These components have been omitted since they are not relevant to a description of a basic system. The support chips shown in figure 5.1 are

• (1) a 1K × 8 read-only memory (ROM)

• (2) a 1/4K × 8 random-access memory (RAM)

• (3) two input ports

• (4) two output ports

Many microcomputers also require a chip known as a system controller (although other names are also used for this chip). This chip takes the control signals produced by the CPU and converts them into the control signals used in the control bus (which in our case are $\overline {MR}$, $\overline {MW}$, $\overline {I/OR}$ and $\overline {I/OW}$). We have dispensed with the system controller in figure 5.1 by the simple device of assuming that the correct control signals are generated by the CPU.