Microprocessor Design Principles and Practices With VHDL Enoch O. Hwang © Brooks / Cole 2004 To my wife and children Windy, Jonathan and Michelle Contents 1. Designing a Microprocessor 2 1.1 Overview of a Microprocessor 2 1.2 Design Abstraction Levels 4 1.3 Examples for a 2-input Multiplexer 4 1.3.1 Behavioral Level 5 1.3.2 Gate Level 6 1.3.3 Transistor Level 6 1.4 VHDL 7 1.5 Synthesis 8 1.6 Going Forward 9 1.7 Summary Checklist 9 Index 11 2 Digital Circuits 2 2.1 Binary Numbers 2 2.2 Binary Switch 4 2.3 Basic Logic Operators and Logic Expressions 5 2.4 Truth Tables 6 2.5 Boolean Algebra and Boolean Function 6 2.5.1 Boolean Algebra 6 2.5.2 Duality Principle 8 2.5.3 Boolean Function and the Inverse 9 2.6 Minterms and Maxterms 12 2.6.1 Minterms 12 2.6.2 Maxterms 13 2.7 Canonical, Standard, and non-Standard Forms 15 2.8 Logic Gates and Circuit Diagrams 15 2.9 Example: Designing a Car Security System 17 2.10 Introduction to VHDL 19 2.10.1 VHDL code for a 2-input NAND gate 19 2.10.2 VHDL code for a 3-input NOR gate 20 2.10.3 VHDL code for a function 20 2.11 Summary Checklist 21 2.12 Exercises 23 Index 26 3 Combinational Circuits 2 3.1 Analysis of Combinational Circuits 2 3.1.1 With a Truth Table 2 3.1.2 With a Boolean Function 4 3.2 Synthesis of Combinational Circuits 5 3.3 Technology Mapping 6 3.4 Minimization of Combinational Circuits 9 3.4.1 Karnaugh (K) Maps 9 3.4.2 Don’t-cares 13 3.4.3 * Quine-McCluskey (Tabulation) Method 14 3.5 * Timing Hazards and Glitches 15 3.6 7-Segment Decoder Example 16 3.7 VHDL Code for Combinational Circuits 19 3.7.1 Structural BCD to 7-Segment Decoder 19 3.7.2 Dataflow BCD to 7-Segment Decoder 22 3.7.3 Behavioral BCD to 7-Segment Decoder 22 3.8 Summary Checklist 23 3.9 Exercises 24 Index 26 4 Combinational Components 2 4.1 Signal Naming Conventions 2 4.2 Adder 2 4.2.1 Full Adder 2 4.2.2 Ripple-Carry Adder 3 4.2.3 Carry-Lookahead Adder 4 4.3 Two’s-Complement Representation for Negative Numbers 6 4.4 Subtractor 8 4.4.1 Adder / Subtractor Combination 8 4.5 Arithmetic Logic Unit 10 4.6 Decoder 14 4.7 Encoder 15 4.7.1 Priority Encoder 16 4.8 Multiplexer 17 4.8.1 Using Multiplexers to Implement a Function 20 4.9 Tri-state Buffer 20 4.10 Comparators 21 4.11 Shifter / Rotator 23 4.12 Multiplier 25 4.13 Summary Checklist 26 4.14 Exercises 27 Index 28 5 Implementation Technologies 2 5.1 Physical Abstraction 2 5.2 Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) 3 5.3 CMOS Logic 4 5.4 CMOS Circuits 5 5.4.1 CMOS Inverter 5 5.4.2 CMOS NAND gate 6 5.4.3 CMOS AND gate 7 5.4.4 CMOS NOR and OR Gates 9 5.4.5 Transmission Gate 9 5.4.6 2-input Multiplexer CMOS Circuit 9 5.4.7 CMOS XOR and XNOR Gates 11 5.5 Analysis of CMOS Circuits 12 5.6 Using ROMs to Implement a Function 13 5.7 Using PLAs to Implement a Function 15 5.8 Using PALs to Implement a Function 19 5.9 Complex Programmable Logic Device (CPLD) 21 5.10 Field-Programmable Gate Array (FPGA) 23 5.11 Summary Checklist 24 5.12 References 24 5.13 Exercises 25 Index 26 6 Latches and Flip-Flops 2 6.1 Bistable Element 2 6.2 SR Latch 4 6.3 SR Latch with Enable 6 6.4 D Latch 7 6.5 D Latch with Enable 7 6.6 Clock 8 6.7 D Flip-Flop 10 6.8 D Flip-Flop with Enable 12 6.9 Asynchronus Inputs 13 6.10 Description of a Flip-Flop 13 6.10.1 Characteristic Table 13 6.10.2 Characteristic Equation 14 6.10.3 State Diagram 14 6.10.4 Excitation Table 14 6.11 Timing Issues 15 6.12 Example: Car Security System – Version 2 16 6.13 VHDL for Latches and Flip-Flops 16 6.13.1 Implied Memory Element 16 6.13.2 VHDL Code for a D Latch with Enable 17 6.13.3 VHDL Code for a D Flip-Flop 18 6.13.4 VHDL Code for a D Flip-Flop with Enable and Asynchronous Set and Clear 21 6.14 * Flip-Flop Types 22 6.14.1 SR Flip-Flop 22 6.14.2 JK Flip-Flop 23 6.14.3 T Flip-Flop 23 6.15 Summary Checklist 25 6.16 Exercises 26 Index 27 7 Sequential Circuits 2 7.1 Finite-State-Machine (FSM) Model 2 7.2 Analysis of Sequential Circuits 3 7.2.1 Excitation Equation 4 7.2.2 Next-state Equation 5 7.2.3 Next-state Table 5 7.2.4 Output Equation 6 7.2.5 Output Table 6 7.2.6 State Diagram 6 7.2.7 Example: Analysis of a Moore FSM 7 7.2.8 Example: Analysis of a Mealy FSM 9 7.3 Synthesis of Sequential Circuits 11 7.3.1 State Diagram, Next-state and Output Tables 11 7.3.2 Implementation Table 11 7.3.3 Examples: Synthesis of Moore FSMs 12 7.3.4 Example: Synthesis of a Mealy FSM 17 7.4 * ASM Charts and State Action Tables 19 7.4.1 ASM Charts 19 7.4.2 State Action Tables 21 7.5 Example: Car Security System – Version 3 22 7.6 VHDL for Sequential Circuits 23 7.7 * Optimization for Sequential Circuits 27 7.7.1 State Reduction 27 7.7.2 State Encoding 28 7.7.3 Choice of Flip-Flops 28 7.8 Exercises 32 7.9 Selected Answers 33 Index 37 8 Sequential Components 2 8.1 Registers 2 8.2 Register Files 3 8.3 Random Access Memory 6 8.4 Larger Memories 8 8.4.1 More Memory 8 8.4.2 Wider Memory 8 8.5 Counters 9 8.5.1 Binary Up Counter 10 8.5.2 Binary Up-Down Counter 11 8.5.3 Binary Up-Down Counter with Parallel Load 13 8.5.4 BCD Up-Down Counter 14 8.6 Shift Registers 15 8.6.1 Serial to Parallel Shift Register 15 8.6.2 Serial-to-Parallel and Parallel-to-Serial Shift Register 17 Index 19 9 Datapaths 2 9.1 General Datapath 3 9.2 Using a General Datapath 4 9.3 Timing Issues 5 9.4 A More Complex Datapath 8 9.5 VHDL for the Complex Datapath 10 9.6 Dedicated Datapath 15 9.6.1 Selecting Registers 15 9.6.2 Selecting Functional Units 15 9.6.3 Data Transfer Methods 16 9.7 Using a Dedicated Datapath 17 9.8 Examples: Designing Dedicated Datapaths 17 9.9 VHDL for a Dedicated Datapath 22 9.10 * Optimization for Datapaths 23 9.10.1 Functional Unit Sharing 23 9.10.2 Register Sharing 23 9.10.3 Bus Sharing 23 9.11 Summary Checklist 23 Index 24 10 Control Units 2 10.1 Exercises 3 10.2 Selected Answers 4 Index 5 11 Dedicated Microprocessors 2 11.1 Manual Construction of a Dedicated Microprocessor 3 11.2 FSM + D Model Using VHDL 11 11.3 FSMD Model 14 11.4 Behavioral Model 16 11.5 Examples 18 Index 25 12 General-Purpose Microprocessors 2 12.1 Overview of the CPU Design 2 12.2 Instruction Set 2 12.2.1 Two Operand Instructions 3 12.2.2 One Operand Instructions 3 12.2.3 Instructions Using a Memory Address 3 12.2.4 Jump Instructions 3 12.3 Datapath 5 12.3.1 Input multiplexer 6 12.3.2 Conditional Flags 6 12.3.3 Accumulator 6 12.3.4 Register File 6 12.3.5 ALU 6 12.3.6 Shifter / Rotator 7 12.3.7 Output Buffer 7 12.3.8 Control Word 7 12.3.9 VHDL Code for the Datapath 8 12.4 Control Unit 9 12.4.1 Reset 10 12.4.2 Fetch 10 12.4.3 Decode 10 12.4.4 Execute 10 12.4.5 VHDL Code for the Control Unit 11 12.5 CPU 20 12.6 Top-level Computer 22 12.6.1 Input 22 12.6.2 Output 22 12.6.3 Memory 22 12.6.4 Clock 23 12.6.5 VHDL Code for the Complete Computer 23 12.7 Examples 24 Appendix A VHDLSummary 2 A.1 Basic Language Elements 2 A.1.1 Comments 2 A.1.2 Identifiers 2 A.1.3 Data Objects 2 A.1.4 Data Types 2 A.1.5 Data Operators 4 A.1.6 ENTITY 5 A.1.7 ARCHITECTURE 6 A.1.8 PACKAGE 7 A.2 Dataflow Model Concurrent Statements 8 A.2.1 Concurrent Signal Assignment 8 A.2.2 Conditional Signal Assignment 9 A.2.3 Selected Signal Assignment 9 A.2.4 Dataflow Model Example 10 A.3 Behavioral Model Sequential Statements 10 A.3.1 PROCESS 10 A.3.2 Sequential Signal Assignment 10 A.3.3 Variable Assignment 11 A.3.4 WAIT 11 A.3.5 IF THEN ELSE 11 A.3.6 CASE 12 A.3.7 NULL 12 A.3.8 FOR 12 A.3.9 WHILE 13 A.3.10 LOOP 13 A.3.11 EXIT 13 A.3.12 NEXT 13 A.3.13 FUNCTION 13 A.3.14 PROCEDURE 14 A.3.15 Behavioral Model Example 15 A.4 Structural Model Statements 16 A.4.1 COMPONENT Declaration 16 A.4.2 PORT MAP 16 A.4.3 OPEN 17 A.4.4 GENERATE 17 A.4.5 Structural Model Example 17 A.5 Conversion Routines 18 A.5.1 CONV_INTEGER() 18 A.5.2 CONV_STD_LOGIC_VECTOR(,) 19 Index 20 Appendix B MAX+plus II Tutorial 2 B.1 Creating a Project and Working with Files 2 B.1.1 Starting a new project 2 B.1.2 Opening an existing project 3 B.1.3 Creating a project based on an existing VHDL source file 3 B.1.4 Importing existing VHDL source files into the project 3 B.1.5 Creating new VHDL source files for the project 3 B.2 Synthesis for functional simulation 4 B.2.1 Starting the compiler 4 B.2.2 Set up input signals 4 B.2.3 Set up and view simulation time range 6 B.2.4 Assign values to input signals 6 B.2.5 Simulation 8 B.3 Synthesis for programming the FPGA 9 B.4 Programming the FPGA 10 B.5 References 11 Max+Plus II Tutorial 1 Using the VHDL Editor Synthesis Simulation Using the Floorplan Editor Downloading a circuit to FPGA [...]... Transistor level design Gate level design Register-transfer level design Behavioral level design Logic symbol Microprocessor Design – Principles and Practices with VHDL Last updated 7/16/2003 12:23 PM Chapter 1 − Designing a Microprocessor Page 10 of 11 VHDL Synthesis Netlist Microprocessor Design – Principles and Practices with VHDL Last updated 7/16/2003 12:23 PM Chapter 1 − Designing a Microprocessor. .. 8 1.6 Going Forward 9 1.7 Summary Checklist 9 Index 11 Microprocessor Design – Principles and Practices with VHDL Last updated 7/16/2003 12:23 PM Chapter 1 − Designing a Microprocessor Page 2 of 11 1 Designing a Microprocessor Being a computer science or electrical engineering student, you have probably assembled a PC You have gone... chips Specifically, I will show you how to design the logic circuit for a microprocessor, which is at the heart of every electronic device This may sound way too complicated, but don’t let that scare you because it is really not all that difficult to understand the basic principles of how a microprocessor is designed We are not trying to design the Pentium microprocessor, but after you have learned... standard building blocks for larger circuits such as the microprocessor These standard combinational and sequential components are usually found in standard libraries and serve as larger building blocks for the Microprocessor Design – Principles and Practices with VHDL Last updated 7/16/2003 12:23 PM Chapter 1 − Designing a Microprocessor Page 4 of 11 microprocessor Different combinational components and... the microprocessor Finally, combining the datapath and the control unit together will produce the circuit for a microprocessor, which can be either a dedicated microprocessor or a general microprocessor Transistors Gates 5 2 Combinational Circuits 3 Flip-flops 6 Sequential Circuits 7 Combinational Components 4 Datapath + 9 Sequential Components 8 Control Unit 10 Dedicated Microprocessor 11 General Microprocessor. .. you reach the end of this book, may be you still would not be able to design this circuit for the P4, but you will certainly have the knowledge of how a microprocessor is designed because you will actually have designed and implemented a working microprocessor Figure 11 The internal circuitry of the Intel P4 CPU 1.7 Summary Checklist Microprocessor Datapath Control unit Finite state machine (FSM) Next-state...Chapter 1 − Designing a Microprocessor Page 1 of 11 Table of Content Table of Content 1 1 Designing a Microprocessor 2 1.1 Overview of a Microprocessor 2 1.2 Design Abstraction Levels 4 1.3 Examples for a 2-input Multiplexer 4 1.3.1... netlist of the circuit rather then machine code The popularity of using VHDL (or Verilog) for designing digital circuits began in the mid-1990s when commercial synthesis tools became available Microprocessor Design – Principles and Practices with VHDL Last updated 7/16/2003 12:23 PM Chapter 1 − Designing a Microprocessor Page 9 of 11 Furthermore, the netlist from the output of the synthesizer can be... model of a computer Microprocessor Design – Principles and Practices with VHDL Last updated 7/16/2003 12:23 PM Chapter 1 − Designing a Microprocessor Page 3 of 11 Control Inputs Data Inputs '0' Control unit 1 s ff Nextstate Logic State Memory Output Logic register Control Signals Datapath 0 y ALU ff register Status Signals Control Outputs Data Outputs Figure 2 Internal parts of a microprocessor Even... Multiplexer As an example, let us look at the design of the 2-input multiplexer from the different abstraction levels At this point, don’t worry too much if you don’t understand how all these circuits are built This is intended just to give you Microprocessor Design – Principles and Practices with VHDL Last updated 7/16/2003 12:23 PM Chapter 1 − Designing a Microprocessor Page 5 of 11 an idea of what . − Designing a Microprocessor Page 2 of 11 Microprocessor Design – Principles and Practices with VHDL Last updated 7/16/2003 12:23 PM 1. Designing a Microprocessor. Transistor level design Gate level design Register-transfer level design Behavioral level design Logic symbol Chapter 1 − Designing a Microprocessor