Page 112 - DCAP210_INTRODUCTION__TO_MICROPROCESSORS

Introduction to Microprocessors

Notes
Figure 7.7: Single-board “Keypad and Calculator Display”

Single-board “keypad and calculator display” microcontrollers of this type were very similar to
some low-end microcomputers of the time, such as the KIM-1 or the Microprocessor I. Some of
these microprocessor “trainer” systems are still in production today, as a very low-cost introduction
to microprocessors at the hardware programming level.

Explain the Discrete digital I/O with the related example.

7.4.8 Single-chip Microcontrollers
With the development of single-chip microcontrollers such as the 8748, it became possible to
combine most of the features of the previous board into a single IC package. Often only the clock
generator remained separate, as it remained easier to use a quartz crystal oscillator than to integrate
a stable clock circuit into a low-cost IC.
Single-chip microcontrollers integrate their necessary memory (both RAM and ROM) on-package
and so do not need to expose their bus through the IC package’s pins. These pins are thus freed-
up for I/O lines. Both of these changes make the design of a single-board microcontroller simpler,
but also less necessary. Single-board development and training systems remained popular, but
there was now less need to provide single-board systems as embeddable components for
production systems.
7.4.9 Program Memory
For production use as embedded systems, the on-board ROM would be either mask programmed
at the chip factory or one-time programmed (OTP) by the developer as a PROM. PROMs often
used the same UV EPROM technology for the chip, but in a cheaper package without the
transparent erasure window. During program development it was still necessary to burn EPROMs,
this time the entire controller IC, and so ZIF sockets would be provided.

Figure 7.8: A Development Board for a PIC Family Device

106 LOVELY PROFESSIONAL UNIVERSITY