M. Amer Iqbal Qureshi
How did Microcontrollers evolve?
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| How did Microcontrollers evolve?
The situation we find ourselves today in the field of microcontrollers had its beginnings in the development of technology of integrated circuits. This development has enabled to store hundreds of thousands of transistors into one chip. That was a precondition for manufacture of microprocessor and the first computers were made by adding external peripherals such as memory, input/output lines, timers and others to it. Further increasing of package density resulted in creating an integrated circuit which contained both processor and peripherals. That is how the first chip containing a microcomputer later known as a microcontroller was developed. In the year 1969, a team of Japanese engineers from BUSICOM company came to the USA with a request that a few integrated circuits for calculators were to be designed according to their projects. The request was set to INTEL company and Marcian Hoff was in charge of the project there. Since having been experienced in working with a computer PDP8, he came to an idea to suggest fundamentally different solution instead of suggested design. That solution presumed that the operation of integrated circuit was to be determined by the program stored in the circuit itself. It meant that configuration would be simpler, but it would require far more memory than the project proposed by Japanese engineers. After a while, even though the Japanese engineers were trying to find an easier solution, Marcian’s idea won and the first microprocessor was born. A major help with turning an idea into a ready-to-use product, Intel got from Federico Faggin. Nine months after his arrival to Intel he succeeded in developing such a product from its original concept. In 1971 Intel obtained the right to sell this integrated circuit. Before that Intel bought the license from BUSICOM company which had no idea what a treasure it had. During that year, a microprocessor called the 4004 appeared on the market. That was the first 4-bit microprocessor with the speed of 6000 operations per second. Not long after that, American company CTC requested from Intel and Texas Instruments to manufacture 8-bit microprocessor to be applied in terminals. Even though CTC gave up this project at last, Intel and Texas Instruments kept working on the microprocessor and in April 1972 Teach Yourself PIC Microcontrollers | www.electronicspk.com | 9 the first 8-bit microprocessor called the 8008 appeared on the market. It was able to address 16Kb of memory, had 45 instructions and the speed of 300,000 operations per second. That microprocessor was the predecessor of all today’s microprocessors. Intel kept on developing it and in April 1974 it launched 8-bit processor called the 8080. It was able to address 64Kb of memory, had 75 instructions and initial price was $360. In another American company called Motorola, they quickly realized what was going on, so they launched 8-bit microprocessor 6800. Chief constructor was Chuck Peddle. Apart from the processor itself, Motorola was the first company that also manufactured other peripherals such as 6820 and 6850. At that time many companies recognized greater importance of microprocessors and began their own development. Chuck Peddle left Motorola to join MOS Technology and kept working intensively on developing microprocessors. At the WESCON exhibition in the USA in 1975, a crucial event in the history of the microprocessors took place. MOS Technology announced that it was selling processors 6501 and 6502 at $25 each, which interested customers could purchase immediately. That was such sensation that many thought it was a kind of fraud, considering that competing companies were selling the 8080 and 6800 at $179 each. On the first day of exhibit, in response to the competitor, both Motorola and Intel cut the prices of their microprocessors to $69.95. Motorola accused MOS Technology and Chuck Peddle of plagiarizing the protected 6800. Because of that, MOS Technology gave up further manufacture of the 6501, but kept manufacturing the 6502. It was 8-bit microprocessor with 56 instructions and ability to directly address 64Kb of memory. Due to low price, 6502 became very popular so it was installed into computers such as KIM-1, Apple I, Apple II, Atari, Commodore, Acorn, Oric, Galeb, Orao, Ultra and many others. Soon appeared several companies manufacturing the 6502 (Rockwell, Sznertek, GTE, NCR, Ricoh, Commodore took over MOS Technology). In the year of its prosperity 1982, this processor was being sold at a rate of 15 million processors per year! Other companies did not want to give up either. Frederico Faggin left Intel and started his own company Zilog Inc. In 1976 Zilog announced the Z80. When designing this microprocessor Faggin made the crucial decision. Having been familiar with the fact that for 8080 had already been developed he realized that many would remain loyal to that processor because of great expenditure which rewriting of all the programs would result in. Accordingly he decided that a new processor had to be compatible with the 8080, i.e. it had to be able to perform all the programs written for the 8080. Apart from that, many other features have been added so that the Z80 was the most powerful microprocessor at that time. It was able to directly address 64Kb of memory, had 176 instructions, a large number of registers, built in option for refreshing dynamic RAM memory, single power supply, greater operating speed etc. The Z80 was a great success and everybody replaced the 8080 by the Z80. Certainly the Z80 was commercially the most successful 8-bit microprocessor at that time. Besides Zilog, other new manufacturers such as Mostek, NEC, SHARP and SGS appeared soon. The Z80 was the heart of many computers such as: Spectrum, Partner, TRS703, Z-3 and Galaxy. In 1976 Intel came up with an upgraded version of 8-bit microprocessor called the 8085. However, the Z80 was so much better that Intel lost the battle. Even though a few more microprocessors appeared later on the market (6809, 2650, SC/MP etc.), everything was actually decided. There were no such great improvements which could make manufacturers to change their mind, so the 6502 and Z80 along with the 6800 remained chief representatives of the 8-bit microprocessors of that time. tải về 3.06 Mb. Chia sẻ với bạn bè của bạn:
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