ECE 171: Introduction to Digital Circuits

Fall 1999

Rev: 10.08.99

Lecture Notes 4

Last Time

• Review of last four gates and introduction to the 4 new gates
• Logic Gates
• Truth Tables
• Boolean Expressions
• Symbols - Traditional and IEEE/ANSI 1984
• Design Examples
• Diodes
• Transistors

This Time

• Introduction to UNIX
• Device Labels
• Introduction to data sheets
  • Fanout
  • Noise Margins
  • Power Consumption

UNIX

• To login you will need your login name and password. If you haven't picked these up already, they can be obtained from SB2 139, SB2 169, PCAT 160, or FAB 60-02.
• When you login one window will open.
• To logout click the logout button in the upper right-hand corner of the screen.
• To start a number of applications click the right mouse button on the background area of the screen (where there are no windows).
• To start netscape type
  > netscape4&
• This will start Netscape (version 4.x) and the & will allow you to still use the command window.
• There are a number of programs that you can use to retrieve and send email including:
  • pine
  • elm
  • netscape4 (I use this)
  • mailtool
  • mail
• To learn more about these or any other command type
  > man application_name
  This will bring up the help pages on that particular application.
• To remotely login to one of the UNIX machines from another UNIX machine, use the following sequence of commands:
  > xhost + (this tells your machine to let other machines send it graphics)
  > telnet psu_machine_name (this begins the process of remotely logging into that machine)
  login: jdoe (enter your login name)
  password: xxxx (enter your password)
  > setenv DISPLAY your_computers_name:0.0 (this tells the PSU machine to send graphics to your machine)
• Important web addresses
  • http://www.ee.pdx.edu/~mcnames/ECE171 Class home page
  • http://www.cat.pdx.edu Computer Action Team's home page - you can find a lot of useful information here.
  • http://www.ee.pdx.edu/~mcnames/ECE171/UnixPrimer.html List of common UNIX commands.
• Common UNIX commands:

ls	Lists the contents of the current directory. Much like dir in DOS.
mkdir dir_name	Creates a directory with the specified file name.
cd dir_name	Changes the current directory to the directory name. If you use .. for the directory name this will move you up to the previous directory.
cp filename1 filename2	Copes filename1 to a new file named filename2.
mv filename1 filename2	Renames filename1 as filename2.
rm filename	Removes (erases) the specified file.
passwd	Use this to change your password. It will prompt you to enter the old password and the new password.
lpr -Pprinter_name file	Prints the specified file on the printer named printer_name. I believe the printer in the lab is named lw10.

Device Labels

• Device labels generally contain a single string of characters with no spaces that can be broken up into 5 catagories. From left to right the catagories are:
  • Manufacturer Code (letters)
    See the book for a list of common manufacturer codes. Note that the manufacturer code is not always accurate, though. For example, Texas Instruments makes devices with the manufactuer code CD and Intel labels devices that they buy from Lattice with the Intel code, even though they don't maintain the data sheet on these devices.
  • Series (numbers)
    For example, we will mostly see 54 series and 74 series. These series have TTL compatable inputs and outputs. 54 is for a military temperature operating range and 74 is for a commercial temperature operating range.
  • Technology Type (letters)
    This code is sometimes omitted. It indicates the type of technology that is used inside of the chip. The book lists about a dozen different technology types, but many more have been developed since the book was written.
  • Device Number (numbers)
    This indicates what type of gates are in the chip.
  • Package (letters)
    This indicates the type of package that the device is manufactured in (e.g. DIP, flat pack, surface mount, etc) and indicates the pinout (i.e. what each pin is connected to).

Data Sheets

• Scope
  Although you won't be tested on transistors, you should be able to understand almost everything on the data sheets except for the circuit diagrams that describe the internal circuits of each gate.
• Noise Margins
  There are two noise margins associated with each gate that represent how much the voltage can change from the output of one gate to the input of another gate of the same type and still operate correctly.
  • The upper noise margin, NMu, is given by NMu = Voh,min - Vih,min
  • The lower noise margin, NMl is given by NMl = Vil,max - Vol,max
• Fanout
  The fanout is a measure of how many logic gates of the same type can be driven by the output of one gate. To calculate the total fanout, FO, you must first calculate the fanout for the high state and for the low state separately.
  • FOh = abs(Ioh,max / Iih,max) where abs(.) denotes absolute value.
  • FOl = abs(Iol,max / Iil,max)
  • The total fanout is given by FO = min(FOh, FOl)
• Power Consumption
  To calculate the maximum power that needs to be supplied by the power supply, Vcc, use the following equation:
  Pmax = Vcc,max * Icc,max
  If there is more than one listing for Icc,max, use the largest value. For example, many TI devices list an Icch,max and an Iccl, max.