Specifications

Chapter 1 - Introduction to Microprocessors
idea what treasure they had. During that year, there appeared on the market a microprocessor
called 4004. That was the first 4-bit microprocessor with the speed of 6 000 operations per
second. Not long after that, American company CTC requested from INTEL and Texas
Instruments to make an 8-bit microprocessor for use in terminals. Even though CTC gave up
this idea in the end, Intel and Texas Instruments kept working on the microprocessor and in
April of 1972, first 8-bit microprocessor appeard on the market under a name 8008. It was able
to address 16Kb of memory, and it had 45 instructions and the speed of 300 000 operations per
second. That microprocessor was the predecessor of all today's microprocessors. Intel kept
their developments up in April of 1974, and they put on the market the 8-bit processor under a
name 8080 which was able to address 64Kb of memory, and which had 75 instructions, and the
price began at $360.
In another American company Motorola, they realized quickly what was happening, so they put
out on the market an 8-bit microprocessor 6800. Chief constructor was Chuck Peddle, and
along with the processor itself, Motorola was the first company to make other peripherals such
as 6820 and 6850. At that time many companies recognized greater importance of
microprocessors and began their own developments. Chuck Peddle leaved Motorola to join MOS
Technology and kept working intensively on developing microprocessors.
At the WESCON exhibit in United States in 1975, a critical event took place in the history of
microprocessors. The MOS Technology announced it was marketing microprocessors 6501 and
6502 at $25 each, which buyers could purchase immediately. This was so sensational that
many thought it was some kind of a scam, considering that competitors were selling 8080 and
6800 at $179 each. As an answer to its competitor, both Intel and Motorola lowered their prices
on the first day of the exhibit down to $69.95 per microprocessor. Motorola quickly brought suit
against MOS Technology and Chuck Peddle for copying the protected 6800. MOS Technology
stopped making 6501, but kept producing 6502. The 6502 was a 8-bit microprocessor with 56
instructions and a capability of directly addressing 64Kb of memory. Due to low cost , 6502
becomes very popular, so it was installed into computers such as: KIM-1, Apple I, Apple II,
Atari, Comodore, Acorn, Oric, Galeb, Orao, Ultra, and many others. Soon appeared several
makers of 6502 (Rockwell, Sznertek, GTE, NCR, Ricoh, and Comodore takes over MOS
Technology) which was at the time of its prosperity sold at a rate of 15 million processors a
year!
Others were not giving up though. Frederico Faggin leaves Intel, and starts his own Zilog Inc.
In 1976 Zilog announced the Z80. During the making of this microprocessor, Faggin made a
pivotal decision. Knowing that a great deal of programs have been already developed for 8080,
Faggin realized that many would stay faithful to that microprocessor because of great
expenditure which redoing of all of the programs would result in. Thus he decided that a new
processor had to be compatible with 8080, or that it had to be capable of performing all of the
programs which had already been written for 8080. Beside these characteristics, many new
ones have been added, so that Z80 was a very powerful microprocessor in its time. It was able
to address directly 64 Kb of memory, it had 176 instructions, a large number of registers, a
built in option for refreshing the dynamic RAM memory, single-supply, greater speed of work
etc. Z80 was a great success and everybody converted from 8080 to Z80. It could be said that
Z80 was without a doubt commercially most successful 8-bit microprocessor of that time.
Besides Zilog, other new manufacturers like Mostek, NEC, SHARP, and SGS also appeared. Z80
was the heart of many computers like Spectrum, Partner, TRS703, Z-3 .
In 1976, Intel came up with an improved version of 8-bit microprocessor named 8085.
However, Z80 was so much better that Intel soon lost the battle. Altough a few more
processors appeared on the market (6809, 2650, SC/MP etc.), everything was actually already
decided. There weren't any more great improvements to make manufacturers convert to
something new, so 6502 and Z80 along with 6800 remained as main representatives of the 8-
bit microprocessors of that time.
Microcontrollers versus Microprocessors
Microcontroller differs from a microprocessor in many ways. First and the most important is its
functionality. In order for a microprocessor to be used, other components such as memory, or
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