Digital Electronics I: Overview of Basic Logic Functions and Combinational Circuits, Slides of Digital Electronics

Download Digital Electronics I: Overview of Basic Logic Functions and Combinational Circuits and more Slides Digital Electronics in PDF only on Docsity! EEE130 Digital Electronics I Lecture #1_2 Dr. Shahrel A. Suandi 1-4 Overview of Basic Logic Functions • Digital systems are generally built from combinations of NOT, AND and OR logic elements • The combinations of these elements can be used for the followings: – Comparison, arithmetic, codes conversion, encoding, decoding, data selection, storage and • This section will only give introduction to these common logics, while the details will be explained in future chapters (Chapter 6) Subtractor, multiplier and divider • Subtractor is used for subtraction – Requires 3 inputs: • 2 inputs • 1 borrow input • Multiplier is used for multiplication – Two inputs/numbers are multiplied at a time – Multiplication is actually a process of multiple time of addition, so we can also use adder for this purpose • Divider is used for division – Two inputs/numbers are used for this purpose – The outputs generated are the quotient and the remainder – Similar to multiplier, divider is actually series of subtractions, comparisons, and shifts adder can be used in conjunction with other circuits for this purpose • Do you know ALU?? – Arithmetic Logic Unit – a unit where all arithmetic operations are done in a microprocessor The Code Conversion Function • Code – set of bits arranged in a unique pattern and used to represent specified information • Function of code converter – to convert one code to another form of code • Example: – Binary BCD (binary coded decimal) – Binary gray code • BCD – binary codes that represent decimal digits. There are only 10 code groups in the BCD systems • Gray Code – used to minimize error, especially in servo (shaft position encoders). Is unweighted and is not an arithmetic code. There are no specific weights assigned to the bit positions The Encoding Function • Encoder – converts information from one form to another form • Example: – Calculator: when button “9” is pressed, then the terminal is HIGH and being as the input to an encoder. This number “9” is then converted into binary, for example “1001” (BCD) The Storage Function • Usage: to retain binary data for a period of time • Example of storage devices: – Flip-flops, registers, semiconductor memories, magnetic disks, magnetic tape, and optical disks (CDs) • Flip-flops – a bistable logic circuit that can store only one bit at a time, either 1 or 0 • Registers – a combination of several flip-flops forms registers, 8-bit register is constructed from eight flip-flops – Shift registers are registers used to shift the bits from one position to another within the register or out of the register to another circuit • Semiconductor memories – used for storing large numbers of bits. E.g.: ROM (permanently or semipermanently stored), RAM (temporarily stored) • Magnetic memories – used for mass storage of binary data. E.g.: floppy disk Examples of registers(1 ) - serial shift register - Serial bits on input line 0101 — 010 — 0 0 01— oO ]] Oo = J 0 0 0 | Initially, the register contains only invalid data or all zeros as shown here. First bit (1) is shifted serially into the register. Second bit (0) is shifted serially into register and first bit is shifted right. Third bit (1) is shifted into register and the first and second bits are shifted right. Fourth bit (0) is shifted into register and the first, second, and third bits are shifted right. The register now stores all four bits and is full. Examples of registers(2) - parallel shift register - Parallel bits on input lines 0 T “| ~ || Initially, the register is empty, O O O O containing only nondata zeros. 1 || All bits are shifted in and O ] O 1 stored simultaneously. 1-5 Fixed Function Integrated Circuit (IC) (2) • Pins Numbering – Pin 1 always marked by an identifier like small dot, a notch, or beveled edge • Complexity Classification for Fixed-Function ICs – SSI (Small-scale integration) – 10 gates – MSI (Medium-scale integration) – 10—100 gates – LSI (Large-scale integration) – 100—10,000 gates – VLSI (Very large-scale integration) – 10,000—100,000 gates – ULSI (Ultra large-scale integration) -- >100,000 gates • Integrated Circuits Technology – You will come across MOSFETs, CMOS, TTL etc. in this topic 1-6 Introduction to Programmable Logic • Types of Programmable Logic Devices – SPLD (Single Programmable Logic Device) – there are PAL and GAL – CPLD (Complex Programmable Logic Device) – FPGA (Field Programmable Gate Array) PLD (Programmable Logic Device) Programming Process • Design Entry • Functional Simulation • Synthesis • Implementation • Timing simulation • Download Other Equipments • The Logic Analyzer • Signal Generator – Waveform generator, function generator • Others: – DC Power Supply Example Digital System 3. MOG) Number of Keypad for emvering tablets per bottle number of tablets. per bottle PP Binary code for preset number Code of lublets per bottle converter :: a fo HIGH closes valve On-site display of _ and advanees Binary code for y total tablets bottled conveyor, LOW actual number of a keeps valve open. tablets in bottle 55u One pulse icine from sensor for each tablet advances counter by'1. HIGH causes new sum to be stored. Pulse resets counter to zero n when next bottle is in place. (Current toral sum A binary code for the total number of tablets is transferred in serial form t along this line for remote display and computer inventory control. x Switching sequence control input