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Digital Fundamentals Introductory Digital Concepts Objectives •Explain the basic differences between digital and analog quantities •Show how voltage levels are used to represent digital quantities •Describe various parameters of a pulse waveform such as rise time, fall time, pulse width, frequency, period, and duty cycle •Explain the basic logic operations of NOT, AND, and OR •Describe the logic functions of the comparator, adder, code converter, encoder, decoder, multiplexer, demultiplexer, counter, and register •Identify fixed-function digital integrated circuits according to their complexity and the type of circuit packaging •Identify pin numbers on integrated circuit packages •Describe the PLD, discuss the various types, and state how PLDs are programmed •Recognize digital instruments and understand how they are used in troubleshooting digital circuits and systems •Show how a complete digital system is formed from the basic functions in a practical application Introductory Digital Concepts 2 Digital and analog quantities Analog signal The choices you have to make when converting an analog signal to a digital representation •samling interval •max/min amplitude level •number of bits (dynamics) etc. HEY WAKE UP! what kind of extra choices you can think of? Digital sampling Introductory Digital Concepts 3 An example of a system of analog electronics I wonder if these are purely analog anymore? The volume can be controlled with buttons digitally? Introductory Digital Concepts 4 An example of a system of mixed analog and digital electronics Source for the comparison was S.J. Cahill: Digital and Microprocessor Engineering. 2nd ed. Introductory Digital Concepts 5 Binary presentation with zeros and ones Ideal pulses Real pulses The levels are specified differently for the families (e.g. TTL, CMOS) Introductory Digital Concepts 6 Waveform characteristics 1 1 f = ,T = T f tW Duty cycle = T 100% Introductory Digital Concepts 7 A Digital waveform carries binary information Introductory Digital Concepts 8 Timing diagrams Introductory Digital Concepts 9 Data transfer Serial Parallel AN EXAMPLE Interfacing TM-6710, digital camera Introductory Digital Concepts 10 Intro to basic logic operations NOT AND Introductory Digital Concepts 11 OR Introductory Digital Concepts 12 Comparison function Introductory Digital Concepts 13 Aritmetic functions -Substraction * Multiplication / Division Introductory Digital Concepts 14 Code conversion - encoder Introductory Digital Concepts 15 Code conversion - decoder Introductory Digital Concepts 16 Data selection – multiplexing/demultiplexing Introductory Digital Concepts 17 Storage SERIAL PARALLEL Introductory Digital Concepts 18 Counting Introductory Digital Concepts 19 Fixed-function ICs (integrated circuits) Introductory Digital Concepts 20 IC Packages Introductory Digital Concepts 21 IC Packages Introductory Digital Concepts 22 Pin numbering Introductory Digital Concepts 23 Classification of complexity for ICs Introductory Digital Concepts 24 Programmable logic devices (PLDs) SPLD advantages: •takes less space •design procedure is faster without rewiring and replacing components Three major types: •SPLD (simple ...) •CPLD (complex ...) •FPGA (field-programmable gate arrays) CPLD Programming •schematic or •text-based approach HDL – hardware description language ABEL, CUPL, VHDL, Verilog FPGAs can have upto 1000 pins! Introductory Digital Concepts 25 Intro to test instruments Digital oscilloscope with 4 channels, color display, diskette drive for storage etc. Can you say what is the biggest difference when using an analog or a digital oscilloscope? Portable oscilloscope for measuring analog/digital signal in e.g. industrial environment Introductory Digital Concepts 26 Typical dual-channel oscilloscope Digital Analog Introductory Digital Concepts 27 Hands on tip Introductory Digital Concepts 28 Logic analyzer Introductory Digital Concepts 29 Logic probe When measuring beware not to induce unwanted shortcircuits which can destroy the D.U.T. (device under test). Introductory Digital Concepts 30 Basic instruments Do not forget the importance of a good power supply: digital devices require usually supply with ±5% regulation! Introductory Digital Concepts 31 Digital application What is the purpose of the comparator (comp)? What happens when the output A = B goes high? Can you say what are the contents of the registers at any given time? Introductory Digital Concepts 32
