Chapter 17 Microprocessor Fundamentals William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Introduction to System Components and Buses Microprocessor –general-purpose device –driven by software –perform a specific task Support Circuitry –data input switches –output data William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Introduction to System Components and Buses Microprocessor –Intel 8085 –Motorola 6800 –Zilog Z80 –reads program instructions –executes instructions drives external buses –to make connected devices perform functions William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Introduction to System Components and Buses Microprocessor –buses groups of conductors routed throughout the system tapped into by various devices share information William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Introduction to System Components and Buses Address Bus –16 bits wide –generated by microprocessor –to select a particular location or IC to be active Data Bus –sends or receives 8 bits of data to or from the address –bidirectional William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Introduction to System Components and Buses Control Bus –varying width depending on processor used –carries control signals –identifies operation Address Decoder –like 74LS138 –ensures that only one IC is active –to avoid bus conflict William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Introduction to System Components and Buses Memory –ROM or EPROM initialization instructions monitor program operating system –RAM volatile used only for temporary storage William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Introduction to System Components and Buses Input Port –provide data to microprocessor via the data bus –octal buffer with tri-state outputs Output Port –talk to the outside world –sends data to output device –octal D flip-flop William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Software Control of Microprocessor Systems Operational changes made with software Accumulator –stores information for the microprocessor Assembly Language –software that drives the microprocessor –mnemonics abbreviation of the operation to be performed William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Internal Architecture of a Microprocessor 8085A software compatible with 8080A See Figure 17-2 –internal architecture –functional block diagram See Figure 17-3 –pin configuration Central Processing Unit (CPU) William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Figure 17-2 Figure 17-3 William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Internal Architecture of a Microprocessor Internal Data Bus General-Purpose Registers –B, C, D, E, H, L Arithmetic Logic Unit (ALU) –arithmetic operations –five flag flip-flops Instruction Register and Decoder –receive instructions interpret and create signals William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Internal Architecture of a Microprocessor Interrupt Control –external digital signal that interrupts the software during execution Stack Pointer –stores address of the last entry on the stack –stack - data storage area in RAM Program Counter –16-bit address of next software instruction William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Instruction Execution Within a Microprocessor See Figure 17-4 Load Accumulator Store Accumulator See Table 17-2 –assembly language and machine code listing William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Figure 17-4 William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Hardware Requirements for Basic I/O Programming Memory-Mapped I/O –input and output devices accessed as if they were memory locations I/O-Mapped I/O –identify input and output devices by an 8-bit port number William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Writing Assembly Language and Machine Language Programs Assembler –translates mnemonic into hexadecimal machine code and stores in memory address Compiler –High-level languages Pascal, FORTRAN, C++, BASIC –get reduced to machine language before execution William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Writing Assembly Language and Machine Language Programs Assembly language translates directly to machine code See Table 17-3 –program in three languages –opcodes William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Survey of Microprocessors and Manufacturers See Table 17-4 William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Summary A system designer should consider using a microprocessor instead of logic circuitry whenever an application involves making calculations, making decisions based on external stimuli, and maintaining memory of past events. A microprocessor is the heart of a computer system. It reads and acts on program instructions given to it by a programmer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Summary A microprocessor system has three buses: address, data, control. Microprocessors operate on instructions given to them in the form of machine code (1’s and 0’s). The machine code is generated by a higher-level language like C or assembly language. William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Summary The Intel 8085A is an 8-bit microprocessor. It has 7 internal registers, an 8-bit data bus, an arithmetic/logic unit, and several input/output functions. Program instructions are executed inside the microprocessor by the instruction decoder, which issues the machine cycle timing and initiates input/output operations. William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Summary The microprocessor provides the appropriate logic levels on the data and address buses and takes care of the timing of all control signals output to the connected interface circuitry. Assembly language instructions are written using mnemonic abbreviations and then converted into machine language so that they can be interpreted by the microprocessor. William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

Summary Higher-level languages like C or Pascal are easier to write than assembly language, but they are not as memory efficient or as fast. All languages must be converted into a machine language matching that of the microprocessor before they can be executed. William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.