1 Microprocessor Microprocessor is a controlling unit of a micro-computer, fabricated on a small chip capable of performing ALU (Arithmetic Logical Unit) operations and communicating with the other devices connected to it. Microprocessor consists of an ALU, register array, and a control unit. ALU performs arithmetical and logical operations on the data received from the memory or an input device. 1.1 Block Diagram of a Basic Microcomputer •Instruction Set: It is the set of instructions that the microprocessor can understand. •Bandwidth: It is the number of bits processed in a single instruction. •Clock Speed: It determines the number of operations per second the processor can perform. It is expressed in megahertz (MHz) or gigahertz (GHz).It is also known as Clock Rate. •Word Length: It depends upon the width of internal data bus, registers, ALU, etc. An 8-bit microprocessor can process 8-bit data at a time. The word length ranges from 4 bits to 64 bits depending upon the type of the microcomputer. •Data Types: The microprocessor has multiple data type formats like binary, BCD, ASCII, signed and unsigned numbers. 1.2 Features of a Microprocessor •Cost-effective: The microprocessor chips are available at low prices and results its low cost. •Size: The microprocessor is of small size chip, hence is portable. •Low Power Consumption: Microprocessors are manufactured by using metal-oxide semiconductor technology, which has low power consumption. •Versatility: The microprocessors are versatile as we can use the same chip in a number of applications by configuring the software program. •Reliability: The failure rate of an IC in microprocessors is very low, hence it is reliable.
1.3 Microcontrollers A microcontroller is a small and low-cost microcomputer, which is designed to perform the specific tasks of embedded systems like displaying microwave’s information, receiving remote signals, etc. The general microcontroller consists of the processor, the memory (RAM, ROM, EPROM), Serial ports, peripherals (timers, counters), etc. 1.4 Difference between Microprocessor and Microcontroller Microcontroller Microcontrollers are used to execute a single task within an application. Its designing and hardware cost is low. Easy to replace. It is built with CMOS technology, which requires less power to operate. It consists of CPU, RAM, ROM, I/O ports. Microprocessor Microprocessors are used for big applications. Its designing and hardware cost is high. Not so easy to replace. Its power consumption is high because it has to control the entire system. It doesn’t consist of RAM, ROM, I/O ports. It uses its pins to interface to peripheral devices. 1.5 Applications of Microcontrollers Microcontrollers are widely used in various different devices such as: •Light sensing and controlling devices like LED. •Temperature sensing and controlling devices like microwave oven, chimneys. •Fire detection and safety devices like Fire alarm. •Measuring devices like Volt Meter.
Architecture of 8051 Microcontroller
2 Instruction Set Architecture 2.1 Introduction Instruction set architecture is a part of processor architecture, which is necessary for creating machine level programs to perform any mathematical or logical operations. Instruction set architecture acts as an interface between hardware and software. It prepares the processor to respond to the commands like execution, deleting etc given by the user. The performance of the processor is defined by the instruction set architecture designed in it. The Instruction Set Architecture (ISA) is the part of the processor that is visible to the programmer or compiler writer. The ISA serves as the boundary between software and hardware. We will briefly describe the instruction sets found in many of the microprocessors used today. The ISA of a processor can be described using 5 categories: Operand Storage in the CPU Where are the operands kept other than in memory? Number of explicit named operands How many operands are named in a typical instruction. Operand location Can any ALU instruction operand be located in memory? Or must all operands be kept internaly in the CPU? Operations What operations are provided in the ISA.