Jonathan A. Titus

Microcomputer Pioneer

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Lesson 5: CPU and Memory

by David G. Larsen, Peter R. Rony, and Jonathan A. Titus

The structure of a microcomputer
IN THIS month's column we shall discuss the structure of a typical microcomputer system, which is shown in Figure 1. This system is based upon the 40-pin 8080 microprocessor chip and possesses all the minimum requirements for a computer, i.e.:
1. It can input and output data.
2. It contains an arithmetic/logic unit (ALU), located within the 8080 chip that performs arithmetic and logical operations.
3. It contains "fast" memory (we believe that speed is an important requirement for a functional computer these days).
4. It is programmable, with the data and program instructions capable of being arranged in any sequence desired.
5. It is digital.
Figure I shows the important data paths within the microcomputer. In the following subsections, we shall dissect this diagram and discuss each of the individual data paths.
Read More: Adobe Acrobat PDF FileThe Structure Of A Microcomputer.pdf [41.3KB]

FIFO Memories
I N THIS MONTH'S COLUMN, we would like to discuss the transfer of data between digital devices whose datahandling speeds are mismatched. This is a common problem in computer interfacing, especially when the rate of data generation bya digital instrument is either considerably faster or else considerably slower than the rate of data acquisition by a computer.

The most common solution to mismatched data rates is to employ a buffer memory, between the digital device and the computer, which "blocks" the data into groups of 64 or 128 words for subsequent transmission to the computer. The computer software required to handle such data blocks is usually simpler than that required to handle the individual data bits.
Read More: Adobe Acrobat PDF FileFIFO.pdf [37.8KB]