MICROPROCESSORS AND ITS APPLIATIONS
Descriptive Answers (in detail)
1. Explain the Evolution of Microprocessors.
Microprocessor is a multipurpose, programmable, clock-driven, register based electronic device that reads binary instructions from a storage device called memory, accepts binary data as input and processes data according to those instructions, and provides as output. A common way of categorizing microprocessors is by the number of bits that their ALU can work time. In other words. a microprocessor with a 4. bit will be referred to as a 4-bit microprocessor, regardless of the number of address lines or the number of data bus lines that it has. Intel 4004 :
The first commercially available microprocessor was the Intel 4004. produced in 1971. It contained 2300 PMOS transistors. The 4004~was a 4 bit device intended to be used with some other devices in making a calculator. Some logic designers, however saw that this device could be used to replace PC boards full of combinational and sequential logic devices. Also the ability to change the function of a system by just changing the programming. rather than redesigning the hardware. is very appealing. Intel 8008 :
In 1972 Intel came out with the 8008. which was capable of working with 8-bit words. The 8008,however required 20 or more additional devices to form a functional CPU. Intel 8080 :
In 1974 Intel announced the 8080. which had a much larger instruction set than the 8008 and required only two additional devices to form a functional CPU. Also. the 8080 used NMOS transistors. so it operated much faster than the 8008. The 8080 is referred to as a second-generation microprocessor. It reqires +12 V power supply. Motorola MC6800
Soon after Intel produced the 8080. Motorola came out with the MC6800. another 8-bit general-purpose CPU. The 6800 had the advantage that it required only a +5-V supply rather than the -5-V. +5-V. and + 12V supplies required by the 8080.
For several years the 8080 and the 6800 were the top-selling 8-bit microprocessors. Some of their competitors were the MOS Technology 6502. used as the CPU in the Apple II microcomputer. and. the Zilog Z80. used as the CPU in the Radio Shack TRS~O microcomputer.
Three major directions of microprocessor Evolutions are
(i) Dedicated or Embedded Controllers
(ii) Bit Slice Processors
(iii) General purpose CPUs
(i) Dedicated or Embedded Controllers:
One direction has been dedicated or embedded controllers. These devices are used to control "smart" machines. such as microwave ovens. clothes washers. sewing machines. auto ignition systems. and metal lathes. Texas Instruments has produced millions of their TMS-1000 family of 4-bit microprocessors for this type of application. In 1976 Intel introduced the 8048. which contains an 8-bit CPU. RAM. ROM. and some I/O ports all in one 40-pin package. Other manufacturers have followed with similar products. These devices are often referred to as microcontrollers. Some currently available devices in this category-the Intel 8051 and the Motorola MC6801. A more recently introduced single chip microcontroller. the Intel 8096. contains a 16-bit CPU. ROM. RAM. a UART. ports. timers. and a 10-bit analog-to-digital converter.
(ii) Bit Slice processors:
A second direction of microprocessor evolution has been bit-slice processors. For some applications. general purpose CPUs such as the 8080 and 6800 are not fast enough or do not have suitable instruction sets. For these applications. several manufacturers produce devices which can be used to build a custom CPU. An example is the Advanced Micro Devices 2900 family of devices. This family includes 4-bit ALUs. multiplexers. sequencers. and other parts needed for custom-building a CPU. The term slice comes from the fact that these parts can be connected in parallel to work with 8-bit words, 16-bit words. or 32-bit words. In other words. a designer can add as many slices as...
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