Basic Digital Logic 2 Combinational Logic Created for the Western Canadian Robotics Society Paul Godin godinp@telusplanet.net February 2004

Basic Digital Logic 2 Review

Review Digital Electronics makes use of 2 states: Logic High, or “1” Logic Low, or “0”

Review There are 3 basic digital gates: AND OR NOT

Review AND, where ALL inputs must be “1” for the output to be “1” OR, where ANY of the inputs can be “1” for the output to be “1” NOT (or the Inverter) where the output is the opposite (compliment) of the input.

Review Questions What is the outcome of the following: 1 1 1 1 1

Basic Combinational Logic, NAND and NOR gates Basic Digital Logic 2 Basic Combinational Logic, NAND and NOR gates

Combinational Logic A circuit that utilizes more that 1 logic function has Combinational Logic. As an example, if a circuit has an AND gate connected to an Inverter gate, this circuit has combinational logic.

Combinational logic How would your describe the output of this combinational logic circuit?

NAND Gate The NAND gate is the combination of an NOT gate with an AND gate. The Bubble in front of the gate is an inverter.

Combinational logic How would your describe the output of this combinational logic circuit?

NOR gate The NOR gate is the combination of the NOT gate with the OR gate. The Bubble in front of the gate is an inverter.

NAND and NOR gates The NAND and NOR gates are very popular as they can be connected in more ways that the simple AND and OR gates.

Exercise 1 – a bit challenging Complete the Truth Table for the NAND and NOR Gates NAND NOR Input Output 1 Input Output 1 Hint: Think of the AND and OR truth tables. The outputs for the NAND and NOR are inverted.

Exercise 2 – more challenging Turn the NAND and NOR gates into inverter (NOT) gates. Include a switch for the input.

Basic Digital Logic 2 Chips and Gates

Basic Digital Chips Digital Electronics devices are usually in a chip format. The chip is identified with a part number or a model number. A standard series starts with numbers 74, 4, or 14. 7404 is an inverter 7408 is an AND 7432 is an OR 4011B is a NAND

Chips Basic logic chips often come in 14-pin packages. Package sizes and styles vary. Pin 1 is indicated with a dot or half-circle Numbers are read counter-clockwise from pin 1 (viewed from the top) Pin 14 Pin 8 Pin 1 Pin 7

Chips Chips require a voltage to function Vcc is equal to 5 volts and is typically pin 14 Ground is typically pin 7 Pin 14 Pin 8 Pin 1 Pin 7

Chips – Specification Sheet Voltage The voltage and ground pins must be connected for the device to function. Check the specification sheet to make sure. Ground Diagram from http://www.onsemi.com

Chips – Specification Sheet B C D Diagrams from http://www.onsemi.com

Wiring a chip IN Vcc IN OUT Probe Vcc

Useful Resources Textbooks on Digital Electronics (used is ok!) Electronics Workbench or other electronic simulation software Craig Maynard’s Virtual Vulcan The following web sites: http://learnat.sait.ab.ca/ict/digi240_godin/default.htm http://learnat.sait.ab.ca/ict/cmph200/Default.htm http://learnat.sait.ab.ca/ict/cmph200_godin/default.htm http://focus.ti.com/docs/logic/logichomepage.jhtml http://www.onsemi.com http://www.national.com/ http://www.play-hookey.com/digital/ http://www.crhc.uiuc.edu/~drburke/databookshelf.html http://www.digikey.ca/

Lab Exercise Using the experimenter’s boards, connect the circuit provided to you in the following pages.

Layout of the SK-10 Experimenter's Board

Layout of the SK-10 Experimenter's Board Flat Side 7400 Wires

Logic Diagram of Lab

End of Basic Digital Logic 2 Copyright WCRS and Paul Godin For non-profit use only