Implementation of Control Unit for Microprocessor Trainer (Arithmetic and Logical Instructions)

Transcription

1 Implementation of Control Unit for Microprocessor Trainer (Arithmetic and Logical Instructions) Phyu Phyu Shein, Tin Tin Khaing Abstract In this paper, the control unit for the 16-bit CPU of a microprocessor trainer is designed, implemented, and tested. The most important part of the control unit is the PIC microcontroller 18F452. The microprogram for the PIC was developed to execute the arithmetic and logical instructions. The control unit of this trainer is designed for NOP, Add, Add Immediate, Add with Carry, Subtract, Sub Immediate, Sub with Borrow, AND, AND Immediate, OR, OR Immediate, XOR, XOR Immediate, Increment, Decrement, Shift Left, Shift Left Carry, Shift Right and Shift Right Carry instructions. The control program was designed to execute the instructions precisely and to reduce executing cycles. The control unit of CPU program is written by using assembly language. Keywords arithmetic and logic unit, control unit, instructions, microprocessor A I. INTRODUCTION MICROCONTROLLER is a complete computer system, including a CPU, memory, a clock oscillator, and I/O on a single integrated circuit. The structure of the storedprogram computer which contains: 1. An input device through which data and instructions can be entered. 2. A storage into which results can be entered and from which instructions and data can be fetched. 3. An arithmetic unit to process data. 4. A control unit to fetch, interpret, and execute the instructions from the storage. 5. An output device to deliver the results to the user. All contemporary computers are being investigated. Commercial computer system development has followed development of hardware technology [4]. Microprocessors are regarded as one of the most important devices in everyday machines called computers. Typical microprocessors incorporate arithmetic and logic functional units as well as the associated control logic, instruction processing circuitry, and a portion of the memory hierarchy [20]. The CPU is the part of a computer in which arithmetic and logical operations are performed and instructions are decoded and executed. The CPU controls the operation of the computer [2]. Phyu Phyu Shein, Assistant Lecturer, Computer Department, Technological University (Dewei), Myanmar, the author was graduated from the University of Computer Studies, Yangon ( maphyu.shein79@gmail.com) Tin Tin Khaing, Assistant Lecturer, Department of Information Technology, Technological University (Pethein), Myanmar, the author was graduated from the University of Computer Studies, Yangon (phone: ; dttk2007@gmail.com) Certain types of basic instructions can be classified as follows. Arithmetic: add or subtract two values Logical: Boolean (e.g., AND, OR, XOR, NOT, etc.) manipulation of one or two values Transfer: retrieve a value from memory or store a value to memory. Branch: jump ahead or back to a particular instruction if a specified condition is satisfied. Arithmetic and logical instructions enable the microprocessor to modify and manipulate specific pieces of data. Transfer instructions enable these data to be saved for later use and recalled when necessary from memory. Branch operations enable instructions to execute in different sequences, depending on the results of arithmetic and logical operations [16]. Most microcontrollers are general purpose microprocessors. So, we often use the terms microcontroller and microprocessor interchangeably. II. RELATED WORK PICs are popular due to their low cost, wide availability, large user base, extensive collect ion of application notes. The main objective of this thesis is to understand the operation of simple RISC to understand the interfacing the CPU, memory, and I/O devices to a common bus. It aims to understand the functions of the basic components of a processor, to visualize how a processor actually executes an instruction and how data flows through its components, to understand assembly language programming of complex commercially available microprocessors/ microcontrollers, to comprehend the basic types and concepts of computer architecture. Processors are used in other advanced electronic systems. They are also used to control consumer electronic devices, to regulate gasoline consumption and antilock brakes in automobiles, to monitor alarm systems, to operate automatic tracking and targeting systems in aircraft, tanks, and missiles and to control radar arrays that track and identify aircraft, among other defense applications. III. MOTIVATION One of the most important digital systems today is the microprocessor. The MIPS instruction set is a very successful microprocessor instruction set architecture (ISA). The benefit of the 16-bit extension of the ISA is that instructions are encoded using fewer bits and thus a program may fit into a significantly smaller amount of memory when using the 16-bit instructions. However, usually the opportunities to use 16-bit instructions are limited such that the savings in memory space. 911

2 IV. CONTRIBUTION The main contribution of this paper is implementation of control unit for microprocessor trainer for arithmetic and logical (ALU) instruction. Figure.1. shows the block diagram of the whole circuit. In this circuit, there are 8 modules which are Processor (CPU) module, Direct Memory Access (DMA) module, Memory module, User Interface (IO CPU) module, Parallel Interface (parallel IO) module, Power module, Display and Keypad modules. To communicate all those modules, data bus (D0 to D15), address bus (A0 to A15), control bus (MEMRD=memory read, MEMWR=memory write, IORD=input/output read and IOWR=input/output write) are used. All modules will be supported by 5V DC from power supply unit. The control unit used this information to generate the necessary signals for executing the instruction. After completing the data path for all instructions, it is necessary to define control signals to execute each instruction Be independently since most data path components are shared for all instructions. The opcode tells the main control unit what is going on inside the data path in sufficient details for it to maintain proper operation of the control signals it sends to the data path via the set of signals The simple RISC instructions are used in this research such as arithmetic and logical instruction supported are shown in Table.1 and Table.2. TABLE I ALU INSTRUCTIONS USED FOR ALU CONTROL UNIT TABLE II SIMPLE RISC INSTRUCTIONS Fig. 1 Complete block diagram of microprocessor trainer V. DESIGN OF THE MICROCONTROLLER-BASED CONTROL UNIT Microprocessor control unit is a very important unit for the computer system. The instructions are needed to control the computer. The control unit fetches an instruction from memory by sending an address and a read command to the memory unit. The instruction word stored at the memory location is then transferred to the control unit. This instruction word, which is in some form of binary code, is then decoded by logic circuitry in the control unit to determine which instruction is being called for. VI. HARDWARE IMPLEMENTATION OF ALU CONTROL UNIT This unit provides the signal that specifies which arithmetic and logical (ALU) operation is to be performed on the present set of data. Some of these operations require two operands and 912

3 while others operate on only one operand. The operations include add, subtract, and, or, xor, logical shift, and arithmetic shift. The output of the ALU goes either to the data memory or through a multiplexer back to the register file. In this system, PIC18F452 is used as CPU PIC in Figure 2. The address enable (AE) and address latch enable (ALE) from CPU are connected to the two74als573b to get 16 bit address for being the 8 bit PIC.16 bit data [D0- D15] are also connected to this latch IC as inputs and output the address [A0 - A15]. PORT B is used as the external interrupt. Memory read (MEMRD) and memory write (MEMWR) are used to connect to the memory module. And then I/O read (IORD) and I/O write (IOWR) are also used to connect to the I/O modules called parallel IO and IOCPU which controls the keypad and display modules. These four memory and I/O control lines are connected with DMA module. It also connects with DMA acknowledge and DMA interrupt from CPU. The oscillator is used with the crystal to get clock inputs and outputs. All address lines [A0- A15] and data lines [D0- D15] are connected to DMA module, memory module, IO CPU module and parallel IO module. The power module gives the required DC power to the CPU. Fig. 3(a) Initialization routine Fig. 3(b) Initialization routine (continue) Fig. 2 Circuit diagram of CPU module VII. SOFTWARE IMPLEMENTATION FOR ALU CONTROL UNIT In this system, the arithmetic and logical (ALU) instructions are fetched, decoded and executed by using microprogram control. Initialization routine, main routine and instruction decode flowcharts are as shown in figures. Fig. 4 Main routine 913

4 Fig. 5(a) Execution of instruction decode Fig. 6 Execution of Add instruction Fig. 7 Execution of Add Immediate instruction Fig. 5(b) Execution of instruction decode (continue) VIII. ALU INSTRUCTIONS EXECUTION A. Arithmetic Instructions In arithmetic instructions, NOP, Add, Add Immediate, Add with Carry, Subtract, Sub Immediate, Sub with Borrow are executed. NOP is no operation. Fig. 8 Execution of Add with Carry instruction 914

5 B. Logical Instructions In logical instructions, AND, AND Immediate, OR, OR Immediate, XOR, XOR Immediate, Increment, Decrement, Shift Left, Shift Left Carry, Shift Right and Shift Right Carry instructions are executed. Fig. 9 Execution of Sub instruction Fig. 12 Execution of AND instruction Fig. 10 Execution of Sub Immediate instruction Fig. 13 Execution of AND Immediate instruction Fig. 11 Execution of Sub with Borrow instruction Fig. 14 Execution of OR instruction 915

6 Fig. 18 Execution of Increment instruction Fig. 15 Execution of OR Immediate instruction Fig. 16 Execution of XOR instruction Fig. 19 Execution of Decrement instruction Fig.17 Execution of XOR Immediate instruction Fig. 20 Execution of Shift Left instruction 916

7 Fig. 21(a) Execution of Shift Left Carry instruction Fig. 23(a) Execution of Shift Right Carry instruction Fig. 21(b) Execution of Shift Left Carry instruction (continue) Fig. 23(b) Execution of Shift Right Carry instruction (continue) Fig. 22 Execution of Shift Right instruction IX. CONCLUSION In this paper, it is impossible to make the control by hardware control, so it is used the software called microprogram control. By using the software or microprogram control, the cycles per instruction cannot be got exactly because it is difficult to adjust them. As used for PIC18F452, instruction sets are more powerful than PIC 16XXX series. Thus, it supports more to reduce the number of cycles per instruction. But 8-bit CPU is used to hold up the instructions; it cannot reduce the numbers of cycle per instruction more. To execute the instructions exactly, the assembly language is used instead of C language in programming. Not to increase the clock speed and to increase the through part of the CPU it should be tested by extending the size of the instruction or designing the instruction again. According to the data from testing, it can be seen to execute the instructions well and correctly. In making to develop the software, it can be supported more to use PIC ICD2 incircuit debugger or ICE 2000 incircuit emulator. 917

8 ACKNOWLEDGMENT I would like to express my heart-felt thanks to Dr. Ni Lar Thein, Rector, University of Computer Studies, Yangon, for her enthusiastic support and permission to carry out this thesis.i would like to deep appreciation to U Kyaw Swa Soe, Pro-Rector, University of Computer Studies, Yangon, U Win Khaine Moe, Deputy Director General, Myanma Science and Technology Research Department, and Professor Daw Nwe Ni, Head of Computer Hardware Technology Department, University of Computer Studies, Yangon, for their valuable suggestions at the seminars and made it possible for me to complete the whole thesis. I would like to acknowledge and express my gratitude to my external examiner Dr. Mie Mie Thet Thwin, Rector, University of Computer Studies, Mandalay, for her kind permission to use the required laboratory instruments in this research. I would like to especially thank my supervisor Professor Dr. Win Aye, Computer University (Mandalay), for her technical and kindly supports doing this research. I also wish to express my deepest gratitude my parents for their encouragement, understanding and support throughout the period of this painstaking research. Finally, my special thanks are due to my teachers who taught and encouraged me during the period of study and those who were directly or indirectly contributed towards the success of this thesis. [19] Murray Sargent III & Richard L. Shoemaker, The IBM Personal Computer From the Inside Out Revised Edition, Addison-Wesley Publishing Company, Inc,1986 [20] Barry B.Brey, The Intel Microprocessor, Architecture, Programming and Interfacing, Fifth Edition, Prentice-Hall, Inc., 2000 REFERENCES [1] David M Calcutt, Frederick J Cowan& G Hassan Parchizadeh, 8051 Microcontrollers, Hardware, Software and Application, John Wiley& Sons Inc., 1998 [2] James Karney, A+ Certification Training Kit, Second Edition, Microsoft Corporation, 2000 [3] Mark Balch, Complete Digital Design, McGraw-HILL, 2003 [4] John P. Hayes, Computer Architecture and Organization, Third Edition, McGraw-Hill, 1998 [5] John L. Hennessy & David A. Patterson, Computer Architecture: A Quantitative Approach, Fourth Edition, Elsevier Inc., 2007 [6] Sajjan G-Shiva, Computer Design and Architecture, Third Edition, Revisedand Expanded, Marcel Dekker, Inc., 2000 [7] David A. Patterson & John L.Hennessy, Computer Organization and Design Third Edition, Elsevier Inc., 2005 [8] Tim Wilmshurst, Designing Embedded Systems with PIC Microcontrollers Principles and Application, First Edition, Elsevier Ltd [9] Ken Arnold, Embedded Controller Hardware Design, LLH Technology Publishing, 2000 [10] Mostafa Abd-El-Barr & Hesham El-Rewini, Fundamentals of Computer Organization and Architecture, John Wiley & Sons,Inc., 2005 [11] Douglas V. Hall, Microprocessors and Interfacing Programming and Hardware, Second Edition, McGRAW- HILL, 1992 [12] S.A.Money, Microprocessor Data Book, McGraw-Hill, 1982 [13] Julio Sanchez & Maria P. Canton, Microcontroller Programming The Microchip, CRC Press, Taylor & Francis Group, LLC, 2007 [14] Nikitas A. Alexandaridis, Microprocessor System Design Concepts, Computer Science Press Inc., 1984 [15] James M. Sibigtroth, M68HC05 Family Understanding Small Microcontroller, Rev 2.0, Motorola Inc [16] Miles J. Murdocca & Vincent P. Heuring, Principle of Computer Architecture, Class Test Edition, Prentice Hall, 1999 [17] Andrew S. Tanenbaum, Structure Computer Organization, Fourth Edition, Prentice Hall of India, 1999 [18] Vojin G. Oklobdzija, The Computer Engineering Handbook, CRC Press,