1 / 31

Computer Logic, Logic Gates, and Building Circuits

Computer Logic, Logic Gates, and Building Circuits. Image: Intel Museum. Logic and Computers. The technology inside of computers (and in fact all logical ideas) is based on several simple logic operations: AND OR NOT These logical operations are related to real world equivalents….

ania
Download Presentation

Computer Logic, Logic Gates, and Building Circuits

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Computer Logic, Logic Gates,and Building Circuits Image: Intel Museum

  2. Logic and Computers • The technology inside of computers (and in fact all logical ideas) is based on several simple logic operations: • AND • OR • NOT • These logical operations are related to real world equivalents…

  3. What does “AND” mean? • When we say “AND,” formally we mean that something is true only when both parts of it are true. • If the stove is on AND water’s in the kettle, then we will make steam. • If either part isn’t there, then the result won’t be true.

  4. What does AND mean in Logic? • AND takes two inputs and produces the value TRUE if both inputs are TRUE’s. • So, with the inputs: T AND T output is: T T AND F output is: F F AND T output is: F F AND F output is: F (Just like in the real world.)

  5. A Truth Table • A truth table is a convenient way to write down the definition of a logic operation. • Let’s use 1’s for True and 0’s for False… • Here’s the table for AND: inputinputoutput 1 1 1 1 0 0 0 1 0 0 0 0 Output of 1 onlywhen both inputsare 1.

  6. Truth Table for OR and NOT OR NOT inputinputoutputinputoutput 1 1 1 1 0 1 0 1 0 1 0 1 1 0 0 0 This just givesthe opposite. We only need one of the inputsto be true, but if both are true,that’s ok, too.

  7. A Logic Gate • A logic gate is a small computer circuit that simulates one of the logic operators we’ve seen. • There are one or two wires that go into the gate that represent the input. • There is one output wire that represents the result of the logic operation. • When the power is on, that means True.

  8. Logic Gates When drawing diagramsof logic circuits, weuse some traditionalshapes for each one. A NOT C If A is off, turn on C. AND AND A A C OR C B B If A and B are on, turn on C. If A or B is on, turn on C.

  9. What have we seen so far? • We saw what a logic gate is. We saw how to use one. • Now we will see how they work inside. • But we will return to the LogSim program later to see how we can combine multiple logic gates together to do useful work.

  10. But what’s inside the box? • How do we build an individual logic gate? • “Pattern on the Stone” chapter 1 shows to build each logic gate from tinker toys, water pipes, or wires. • But real computers today use logic gates built out of small electronic devices. Image: Tinkertoy Website

  11. “OR” Gate from Tinker Toys spring Pushing a pole to the right means TRUE. moveable Push either one of theseto make the output polemove. Not moveable

  12. Building Gates from Wires Flipping a switch means TRUE for input. Lighting-up means TRUE for output. + - AND OR + - How many switches must you turn on in eachcircuit in order for the light bulb to light up?

  13. Real Computers • Real computers are not built from tinker toys or any of the other wacky approaches shown in the “Pattern on the Stone.” • Computers today use logic gates that are built out of small electronic devices called “transistors.”

  14. Transistors are miniature electronic switches. Similar to a light switch, transistors have two operating positions, on and off. This on/off functionality is used to build logic gates. What’s a Transistor Image: Intel Museum

  15. Why are transistors special? Transistors are like real switches, but – 1. They have no moving parts. 2. They can be turned on and off by an electric signal. 3. You could hook the output of one switch to the input of another since they both use electricity! So that means – They are small and fast. In fact, as transistors get smaller and faster, so do computers. ControlSignal Image: Intel Museum

  16. Computers Get Smaller: ENIAC • The tremendous size of the first electronic computer, built here at Penn, was because the transistors used to built it were the size of lightbulbs. • Modern transistors are microscopic. • That’s what we have laptop and handheld computers nowadays. Image: Van Pelt Library ENIAC Exhibit

  17. Sizes of Transistors Look at the transistors samples in class. “Moore’s Law” is a famous observation that: Researchers tend to shrink transistor sizes in half every 18 months. Transistors shrink so we can make chips smaller and fit more on a single chip. Image: Intel Research

  18. A Transistor • A transistor controlswhether a switch ison or off. • It turns off its switch when it’s given an electric signal. • When there is no power on the signal line, the transistor turns the switch on. Transistor signal

  19. A Transistor • A transistor controlswhether a switch ison or off. • It turns off its switch when it’s given an electric signal. • When there is no power on the signal line, the transistor turns the switch on. TransistorOFF signalON

  20. A Transistor • A transistor controlswhether a switch ison or off. • It turns off its switch when it’s given an electric signal. • When there is no power on the signal line, the transistor turns the switch on. TransistorON signalOFF

  21. Logic Gates from Transistors • For example, we will build a NOT gate from a transistor. extrapowersource Transistor Output fromNOT gate. Input toNOT gate.

  22. Logic Gates from Transistors • For example, we will build a NOT gate from a transistor. extrapowersource TransistorOFF Output fromNOT gateis OFF. Input toNOT gateis ON. NOT 1  0

  23. Logic Gates from Transistors • For example, we will build a NOT gate from a transistor. extrapowersource TransistorON Output fromNOT gateis ON. Input toNOT gateis OFF. NOT 0  1

  24. Summary: A Hierarchy of Parts • We started with TRANSISTORS. • We built some LOGIC GATES. Can we build useful stuff out of logic gates?How can we combine them?

  25. What we want… “Normal” OR ININOUT1 1 01 0 10 1 1 0 0 0 ININOUT1 1 11 0 10 1 1 0 0 0 Building “Exclusive OR” • One or the other but not both. • Different than “OR.” _

  26. What we want… “Normal” OR ININOUT1 1 0101011 0 0 0 ININOUT1 1 11 0 10 1 1 0 0 0 Building “Exclusive OR” • One or the other but not both. • Different than “OR.” • Want output TRUE when either:Input 1 is TRUE and Input 2 is FALSE orInput 1 is FALSE and Input 2 is TRUE

  27. What we want… “Normal” OR ININOUT1 1 0101011 0 0 0 ININOUT1 1 11 0 10 1 1 0 0 0 Building “Exclusive OR” • One or the other but not both. • Different than “OR.” • Want output TRUE when either:Input 1 is TRUE and Input 2 is FALSE orInput 1 is FALSE and Input 2 is TRUE Can replace False with NOT TRUE.

  28. Building “Exclusive OR” • Want output TRUE when either:Input 1 is TRUE and Input 2 is NOT TRUEorInput 1 is NOT TRUE and Input 2 is TRUE AND NOT Input 1 OR Output Input 2 AND NOT

  29. What we want… ININOUT1 1 11 0 00 1 0 0 0 0 If there’s extra time… • Can we build an AND circuit using only NOT and OR gates?

  30. If there’s extra time… AND should be FALSE if either Input 1 is NOT TRUE or Input 2 is NOT TRUE. Input 1 NOT OR Output NOT Input 2 NOT

  31. Credits The Intel Museum: http://www.intel.com/education/transworks/ Intel Research Website: http://www.intel.com/research/silicon/mooreslaw.htm Van Pelt Library ENIAC Exhibit: John W. Mauchly and the Development of the ENIAC Computer http://www.library.upenn.edu/exhibits/rbm/mauchly/jwm0-1.html Tinker Toys Website: http://www.hasbro.com/tinkertoy/

More Related