Advanced Digital design Lecture1 Assist. Prof. Rassim Suliyev - SDU 2018

Course Materials All needed Software and course materials will be located on http://instructor.sdu.edu.kz/~rasmus inside the Advanced Digital Design directory Materials that are used in this slides are taken from the textbook “Digital Electronics A Practical Approach with VHDL” by William Kleitz

INTRODUCTION Digital circuitry is the foundation of digital computers Home appliances, alarm systems heating systems, automated machine control inventory management, medical electronics, etc… Digital electronics evolved from transistor circuitry easily be fabricated designed to output one of two voltage levels 1 - HIGH (usually +5 volts) 0 – LOW (usually 0 Volts)

Digital versus Analog Systems operate on discrete digits numbers letters symbols etc… deal strictly with ON and OFF represent by 0s and 1s Analog measure and respond to continuously varying electrical or physical magnitudes Temperature Pressure Velocity Position Etc…

Digital versus Analog Systems So why do we need to use digital representations in a world that is naturally analog?

Digital Representations of Analog Quantities

Noises

Review Questions Complete the following sentences with the word analog or digital: Wind speed is an example of a(an) _______ quantity? A music CD contains _______ information? A USB connector transmits _______ data? Hourly outdoor air temperatures exhibit _______ variations? An automobile speedometer display is (digital, analog, or could be either) An analog-to-digital converter outputs an analog voltage. True or false?

Number Conversions binary octal hexadecimal

BCD and Symbol Represenation The binary-coded-decimal (BCD) system is used to represent each of the 10 decimal digits as a 4-bit binary code. This code is useful for outputting to displays that are always numeric (0 to 9), such as those found in digital clocks or digital voltmeters. ASCII - American Standard Code for Information Interchange The ASCII code uses 7 bits to represent all the alphanumeric data used in computer I/O.

Digital Signals A digital signal is made up of a series of 1s and 0s that represent numbers, letters, symbols, or control signals

Clock Waveform Timing Special clock and timing circuits are used to produce clock waveforms to trigger the digital signals at precise intervals

Serial vs Parallel uses a single electrical conductor can only transmit 1 bit for each clock period generally used in computer- to-computer communication uses a separate electrical conductor for each bit to be transmitted, thus is fast generally used in data transfer inside the computer

Review Questions Why is ASCII code required by digital computer systems? What is the relationship between clock frequency and clock period? What advantage does parallel have over serial in the transmission of digital signals?

Switches in Electronic Circuits transitions between 0 and 1 are caused by switching from one voltage level to another (0V, 5V) make and break a connection between two electrical conductors manual switch electromechanical relay semiconductor devices (diodes, transistors)

A Relay as a Switch controlled by external voltage often used to deliver signals to a high power load

A Relay as a Switch Advantage: it provides total isolation between the triggering source and the output Disadvantages: High power consumption (triggering device must supply several mA whereas a semiconductor requires only a few uA to operate) Speed (take several ms to switch, compared to us for a semiconductor switch)

A Diode as a Switch semiconductor device that allows current to flow only in one direction current will flow only if the anode is more positive than the cathode

1. Determine if the diodes are forward or reverse biased? 2. Determine V1-V6 (with respect to ground) for the circuits?

A Transistor as a Switch three-terminal semiconductor component allows an input signal at one of its terminals to cause the other two terminals to become a short or an open circuit commonly made of silicon N-type (one more electron) P-type (one less electron) three distinct regions emitter, base, collector N-P-N-type or P-N-P

NPN vs PNP NPN transistor applying a positive voltage from base to emitter causes the collector-to-emitter junction to short (turn ON) applying a negative voltage or 0 V from base to emitter causes the collector-to-emitter junction to open (turn OFF) PNP transistor applying a negative voltage from base to emitter turns it ON. applying a positive voltage or 0 V from base to emitter turns it OFF

A Transistor as a Switch

The TTL Integrated Circuit TTL (Transistor–transistor logic) use a combination of several transistors, diodes, and resistors integrated together in a single package Q1 - input transistor (drives Q2) Q2 controls Q3 and Q4 D1 protects Q1 from negative voltages D2 ensures Q4 cut off when Q3 is saturated

The idea of needing a variable RC resistance is accommodated by the TTL integrated circuit. It uses another transistor (Q4) in place of RC to act like a varying resistance. Q4 is cut off (acts like a high RC) when the output transistor (Q3) is saturated, and then Q4 is saturated (acts like a low RC) when Q3 is cut off.

The CMOS Integrated Circuit CMOS – complementary metal oxide semiconductor uses a complementary pair of metal oxide semiconductor field-effect transistors (MOSFETs) advantage is its low power consumption disadvantages compared to TTL: switching speed is slower burnout due to electrostatic charges Details about TTL and CMOS discussed later in further lectures

Integrated Circuit Chips

Review Questions How does a normally open relay differ from a normally closed relay? To forward bias a diode, the anode is made more ___________ (positive/negative) than the cathode. To turn ON an NPN transistor, a ___________ (positive/negative) voltage is applied to the base.

Simulation of Switching Circuits MultiSIM - software simulation tool provides an accurate simulation of digital and analog circuit operation simulation of instruments to measure IC, component, and circuit characteristics Download and install from: http://instructor.sdu.edu.kz/~rasmus/ Follow Advanced Digital Design -> Software directories

Grading Policy MT1 – 30% MT2 – 30% FIN – 40% Class work (until week 8) – 15% Paper based Midterm (on week 8) – 15% MT2 – 30% Class work (weeks 9 - 15) – 15% Attendance (weeks 1-15) – 15% FIN – 40% Project – 20% Paper based Final Exam – 20%