MODULE-1 Introduction to Microprocessor: Microprocessor is an electronic chip that functions as the central processing unit (CPU) of a computer. The microprocessor based systems with limited resources are called as microcomputers. Now-a-days microprocessors are found in almost all electronic machines and appliances in its different form. Some common devices using microprocessors are computer, printers, automobiles, washing machines, microwave ovens, mobile phones, fax machines, Xerox machines and advanced instruments like radar, satellites, flights etc. Almost all microprocessors use the basic concept of “stored program execution”. By this concept, programs are stored sequentially in memory locations. The microprocessor will fetch the instructions one after the other and execute them in its arithmetic and logic unit. So it is necessary for the user to know about the internal resources and features of the microprocessor. The programmers must also understand the instructions that a microprocessor can support. Every microprocessor will have its own associated set of instructions and this list is given by all the microprocessor manufacturers. Programs are written using mnemonics called the assembly level language and then they are converted into binary machine level language. This conversion can be done manually or using an application called assembler. In general, the programs are written by the user for a microprocessor to work with real world data. These data are available in many forms and are from many sources. A microprocessor based system need a set of memory units, set of interfacing circuits for inputs and a set of interfacing circuits for outputs. All circuits put together along with microprocessor are called as microcomputer system. The physical components of the microcomputer system are in general called as hardware. The program which makes this hardware useful is called as software. Origin of Microprocessor The breakthrough in transistor technology led to the introduction of minicomputers of the 1960s and the personal computer revolution of the 1970s.Microprocessors evolution is categorized into five generations i.e.first, second, third, fourth, and fifth generations. First Generation (1971-73) The microprocessors that were introduced in 1971 to 1972 were referred to as the first generation systems. Intel Corporation introduced 4-bit 4004 at 108 kHz, the first microprocessor in 1971, codeveloped by Busicom, a Japanese manufacturer of calculators. In 1972, Intel made the 8-bit 8008 and 8080 microprocessors. Second Generation (1974-78) The second generation marked the beginning of very efficient 8-bit microprocessors. Some of the popular processors are Motorola’s 6800 and 6809 and Intel’s 8085, Zilog’s Z80. The distinction between the first and second generation devices is primarily the use of newer semiconductor technology to fabricate the chips. They were manufactured using NMOS technology. Third Generation (1979-80)
Introduced in 1978, dominated by Intel’s 8086 and the Zilog Z8000, which were 16-bit processors, have 16-bit arithmetic and pipelined instruction processing. Fourth Generation (1981-95) Intel introduced 32 bit processor, 80386 and Motorola 68020/68030. Fabricated using low-power version of the HMOS technology called HCMOS. Fifth Generation (1995 till date) Chips carry on-chip functionalities and improvements in the speed of memory and I/O devices. Design surpassed 10 million transistors per chip. Introduction of 64-bit processors.Intel leads the show with Pentium, Celeron and dual and quad core processors working with up to 3.5GHz speed. Intel 8085 Microprocessor Introduction 8085 is an eight bit microprocessor of Intel Corporation, usually called as a general purpose 8-bit processor. It is upward compatible with microprocessor 8080, which is the earlier product of Intel. Several faster versions of 8085 microprocessor are 8085AH, 8085AH-1, and 8085AH-2. A microprocessor system consists of three functional blocks: central processing unit (CPU), input and output units, memory units as shown in figure1.1. The central processing unit contains several registers, arithmetic logic unit (ALU) and control unit. Figure1.1: Microprocessor System
Microprocessor is an integrated chip that functions as the central processing unit of a computer. The microprocessor basically performs • • • • • Memory Read: Accept data (instruction) from memory. Memory Write: Send data to memory. I/O Read: Accept data from input device. I/O Write: Send data to output device. Controls timing of instruction flow. Memory includes ROM (read only memory) and RAM (random access memory or read write memory).The memory • Stores instructions and data. • Provides the instructions and data to processor. • Stores results. The input devices enter instructions and data to processor. The input device includes Key-Board (Hexadecimal / ASCII), Switches, and Analog-to-Digital (A/D) convertor. The output devices accept data from processor. This includes LED (Light Emitting Diode) display, LCD (Liquid Crystal Diode) display, CRT (Cathode Ray Tube) Screen. Architecture The internal block diagram of 8085 is shown in figure 1.2. It is a 40 pin IC package and uses +5V for power. It can run at a maximum frequency of 3MHz. It is a 8-bit processor which has a data bus of 8bits wide. It has addressing capability of 16-bit.That is it can address 216 = 64K Bytes of memory (1Kbyte =1024 byte). The architecture of 8085 processor consists of five functional units: Arithmetic and logic Unit, General purpose registers, Special Purpose Registers, Instruction register/decoder and Timing and control unit.
Figure 1.2: Architecture of 8085 Pin Diagram of 8085