Understanding Computer Electronics: Integrated Circuits and Logic Gates

TEJ2O – Grade 10 Computer Engineering – Computer Electronics Notes Computer electronics notes What is an Integrated Circuit? • Integrated Circuit (Chip): small plastic or ceramic package for electric conductors o 2 to a few hundred connections from the outside o 1000s of types of integrated circuits o Gate Identification Number: identifies what type of gate this chip is, along with an indentation to know what orientation it should be. o Pins: connects the chip to the breadboard holes from which information is passed o Bus (in hardware): moves data from one place to another o Bus (chip level): a set of pins that perform a common task § Labeled alphabetically (Bus A, Bus B, Bus C…) • Gates: a barrier or switch that controls how electricity should flow through the computer o AND, OR, NOT, NAND, EOR/XOR What is Illustrating Flow of electricity? ● Methods of Illustration: Displays the flow of low voltage through gates and chips. ● schematic diagrams, truth tables, and boolean algebra are examples of diagrammatic representations. ● Gate Schematic: pictorial representation of a gate, consisting of letters, lines and figures to illustrate the flow of electricity in and out of the gate. o Looks like an elongated “D” shape o A and B lines represent input of electricity o Y line represents output o Actual flow of electricity carried out by several transistors inside the gate ● Chip Schematic: pictorial representation of the organization of a number of gates into a single chip o Numbered rectangles on the side of the diagram represent the pins o VCC pin must be connected to a low voltage power source o GND pin must be connected to ground ● Truth Tables: numerical representation of the inputs into a gate, and the outputs from a gate, recorded in binary in a column format. o First Column: input (A) o Second Column: input (B) o Third Column: output (Y) o AandBflowsinatthesametime o Records all the possible inputs and outputs of the circuit ● Boolean Algebra (Boolean Equations): provides a very precise way of illustrating the logic of computer chips. o George Boole developed this new way of using algebra to represent logic flows of electricity Computer Engineering – TEJ2O1 – Integrated Circuits Page 1 olEg: Y=A*B What are Gates and Chip? • AND Gate o o Elongated capital D shape o A and B on left represent input o Y represents output o Each input can be 1 (on) or 0 (off) o Equation: y = AB Truth Table o YisononlywhenAandBareon. o 74LS08 (AND) Chip § Quad two-input AND gate chip § Chip has 14 Pins, connected directly to the inner circuitry § Pin 7 is a grounding (GND) pin, pin 14 is has positive +5 volts of A B Y 0 0 0 0 1 0 1 0 0 1 1 1 power Gate Number (AND) gate Input Pins Output Pins Other Pins 1 1,2 3 7 Ground 2 4,5 6 14 +5 Volts 3 9,10 8 4 12,13 11 • OR Gate o elongated D with curved back and pointed tip o o equation:Y=A+B Computer Engineering – TEJ2O1 – Integrated Circuits o “+” means OR, not add o IfeitherAorBareon,Ywillalsobeon o 74LS32 Chip Gate number and IO pins same as AND chip (74LS08) • NOT Gate o o NOT gate looks like a sideways triangle with a circle on the tip of NOR gate only has 1 input (A) o Equation: Y = o Y will always be the opposite of A o Inverter: when the output is opposite of the input o The line above A indicates that the signal is switched What are laws in Boolean Algebra? What is emulation? What is Negated AND? A B Y 0 0 0 0 1 1 1 0 1 1 1 1 Computer Engineering – TEJ2O1 – Integrated Circuits