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COCO
Names of Team Members
ACTIVITIES FOR SESSION
Student ID Numbers
8
Section
Today:
1. TTL Gates and Data Sheets (Sec.3.5)
Activity 8.1 – Reading data sheets, and LogicWorks™ simulation
2. Working with Hardware
Activity 8.2 – Build and test a combinational logic circuit with real
hardware
Hand in Today for Grading:
Activities 8.1, 8.2 (one per team, signed off by your TA).
Read for Next Class:
Section 4.1,4.2 until 4.2.3
8.1
8.2
Sum
___________________________________
Grader’s Signature
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Activity 8.1: TTL Gates and Data Sheets (Sec.3.5)
Using the attached pages from the TTL data book, or preferably, from the data book itself1,
answer the following questions.
a. (6 points) Use the index, or the section titled “selection information” to locate the part
numbers for the following devices. For each case, keep in mind that we need the “LS”
type of devices. LS stands for “low-power schottky”, and this is the type that is
available in the laboratory.
The first one has been done for you.
Description of the device
A chip with four 2-input NAND gates with
standard two-state outputs, and standard
voltage levels.
Part Number
74 LS 00.
We found this on page 1-3 of the Selection Guide. We
looked up a table for “NAND gates” and picked out
“Quad 2-input NAND gates”. Then, we looked up
“2S” in the second column and then checked the fourth
column to make sure that this part was available in
low-power schottky (“LS”). Then, we read off the
number “00” from the third column. The part number
is always of the form “74LSxx”. The detailed
description of this part is on page 5-2 of the TTL data
book.
A chip with 2-input Exclusive OR gates with
standard two-state outputs, and standard
voltage levels.
A chip with 4-input AND gates with standard
two-state outputs, and standard voltage
levels.
A chip with 4-input OR gates with standard
two-state outputs, and standard voltage
levels.
Hint: If you cannot find a part that directly fits your needs,
look to other manufacturers first, and then consider
synthesizing the part yourself out of other available parts.
1
The TTL data book is also on the web at http://www.mot-sps.com/books/html
Computer Components and Operations, Fall 1998
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b. (20 points) Study the detailed description for the 74LS00 chip with standard two-state
outputs, and standard voltage levels, and answer the following questions.
Question
How many pins does this chip have?
We usually use the plastic or ceramic
packaging in the laboratory.
How do we recognize pin #1?
Answer
To which pin(s) do we apply power?
Which pin is set to ground (0 volts)?
What is the typical power supply
voltage?
What is the worst-case gate delay for
this device?
What range of input voltages are
considered “Logic 0”?
What range of input voltages are
considered “Logic 1”?
List all the input pins on this chip by
pin number
List all the output pins on this chip by
pin number
Computer Components and Operations, Fall 1998
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c. (10 points) Consider the following combinational circuit:
1
0
X
1
0
Y
0
Z
Build and test this circuit using LogicWorks using the “7400 devs” library instead of the
“primgate” library that you have used before. Demonstrate that your circuit has the correct
truth table by writing down the Boolean expression for the above circuit, and tabulating the
expected and observed outputs in the table below. This would be a simulation of a circuit
built using the “74xx series” TTL logic gates.
Boolean Expression for Z = _____________________________
X
0
0
1
1
Y
0
1
0
1
Z from Boolean Expression Z from Logicworks simulation
Attach a printout of your schematic, with the names of the team members clearly indicated.
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Activity 8.2: Working with Hardware
In this activity, we will build and test the same circuit as in Activity 8.1, but this time with
real hardware. Follow the steps listed on the attached pages. Show your working circuit to the
grader and have the following table filled in.
Hardware Activity Signoff Sheet
Hardware works as specified (10 points)
Clean and organized wiring (5 points)
Good circuit layout (5 points)
Supply bypass capacitors were wired
correctly (5 points)
Cleanup was done properly(5 points)
Total
___________________________________
Grader’s Signature
Computer Components and Operations, Fall 1998
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COCO
LABORATORY PRACTICES
Step 1: Obtaining the equipment
One team member should go to the left back door of the studio and check out a “prototyping
board”. You may need to deposit your Rensselaer ID card for this with the TA. You must
write down the names of the team-members on this board. You will use this protoboard for
the duration of this course, and it should be returned in the same condition you received it in.
Another team member should go to the right back door of the studio and check out a toolbox.
Again, you may need to deposit your Rensselaer ID card for this with the TA. The toolboxes
will be shared between students in other sections as well as students in other courses, and
should be handled very carefully.
The chips are stored in the cabinet on the left end of the studio in labeled boxes. You must
return the chips to the proper boxes after use. A list of all available devices is attched at the
end of this handout, and is also available from the course web page.
Step 2: Getting to know the equipment
A. The toolbox
The toolbox consists of the following items:
Multi-meter
Use this to measure voltages, resistances, currents, etc.
Logic probe
Use this to probe the logic levels (0 volts and 5 volts). Connect the red wire
to +5volts, and the black wire to ground (0 volts). Touch the tip of the probe
to a part of your circuit to determine its logic level. The small lights on the
probe indicate the logic levels.
Wire stripper Use this to strip the plastic insulation off wires. Make sure that the stripped
plastic is properly disposed of in the trash can.
Wire cutter
Use this to cut wires. Make sure that the small wire pieces are properly
disposed of in the trash can.
Long nose
Use this for bending wires.
pliers
Chip puller
Use this carefully to pull chips off the protoboard.
Screw driver Use this to adjust device such as trimmed potentiometers.
Power leads
Use these to connect the power supply to the universal protoboards. Use the
following color convention: Red: +5 volts; Green/Black: Ground (0 volts);
Purple: -12 volts; Yellow: +12 volts.
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B. The prototyping board
You will do all your wiring on Universal Protoboards (prototyping boards). These boards (see
1
2
Figure 1) were custom fabricated at RPI for this course. The parts labeled
and
will
be needed for the second half of this course and we’ll not worry about them now.
3
You will build all your circuits in the areas labeled
and 4 . This area consists of an
array of holes separated 0.1 inch from each other. The pins on integrated circuits (ICs),
commonly referred to as “chips” are also separated 0.1 inch. The holes on the protoboard are
connected internally in rows and columns as explained below.
3
The areas labeled
in Figure 1 have two columns of holes each. These holes are
connected together lengthwise, as indicated in Figure 2. These buses are usually used for
power and ground connections. Do not place components such as integrated circuits (ICs) on
this bus.
1
2
3
4
5
6
7
8
9
BA
COM
A
COM
A
B
B
-12V
GND
+12V
1
+5V
60
UNIV ERSAL PROTOBOARD
4
3
2
1
Figure 1: The universal protoboard that you will use in the laboratory.
4
The areas labeled
in Figure 1 have holes that are connected in the other direction. This
part of the protoboard is where you will place ICs and discrete components such as resistors,
capacitors, etc. Refer to Figures 2 and 3 for proper placement and connection of ICs. In
these figures, there is a +5V "bus" and a GND "bus". Any wire connected to this bus will be
connected to either +5V or GND (provided these power signals have been connected from
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the power supply). It is a good practice to always use red colored wires for +5V lines and
black wires for GND lines. The black object in these diagrams represents an IC (Integrated
Circuit) which you will use in this course. All ICs have a notch or dot at one end that helps us
figure out their orientation. The pins are usually numbered counter-clockwise starting from
the pin below the notch (when viewed from above). For instance, Figure 3 shows pin number
11 of this IC connected to GND, and pin number 22 connected to
+5V.
Use these for
+5V and GND
Insert ICs in the
middle like this,
noting the position
of the notch
Use these
holes to
connect pins
of ICS to
multiple
places
Figure 2: Showing how the protoboards are wired internally (shown by the thick arrows),
and also the procedure for placing chips.
+5V
Notch
pin 1
GND
Figure 3: Showing the connection of ICs. In particular, this diagram shows pin number 11 of
this IC connected to GND, and pin number 22 connected to +5V.
Some guidelines for wiring circuits


Plan your layout in advance: Look at the way the pins are arranged on each chip and try
to place your chips on the protoboard so that they can be connected easily.
Modular layout: When you have to build a large circuit, it makes sense to build it in
small pieces (“modules”) that can be tested independently, and subsequently connected
together. Later, when you are trying to debug your circuit, it makes sense to disconnect
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


the major modules, and test them independently. Try to plan your layout with such
modularity in mind.
Test each part beforehand: It is often possible for you to encounter chips that are
defective. It is a good idea to test each chip before it goes into a complicated circuit. It is
a lot harder to locate a defective chip later!
Color coding of wires: Be very neat, and follow a systematic color scheme for your
wires (see Figure 4 below). For instance, the color red is typically used for +5volts and
black is usually used for Ground (0 volts). Use other colors in a systematic manner. This
will help you debug your circuits more easily.
Avoid “loops”: Try to connect any pair of points in your circuit with a wire that runs
close to the protoboard, and is as short as possible. Whenever we have wires that stick out
to form “loops” on the board, we run the risk of this loop acting as an antenna, and
introducing unwanted electrical disturbances into our circuits.
Bad Wiring!

Better
Figure 4: An example of good wiring.
Use supply bypass capacitors: Ideally, the power supply is a rock-steady voltage
waveform at +5V and 0V. In practice, however, the supply waveform is "noisy", i.e., it
has a small rapidly-fluctuating component. This fluctuating component is usually because
of surge currents drawn by each of the little transistors in our digital system, and because
of the inability, due to high inductance, of the power supply to meet these surge current
requirements. Also, every now and then, one may find large transient fluctuations. These
effects can sometimes become large enough to cause unwanted changes in our digital
Computer Components and Operations, Fall 1998
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circuit. "Supply Bypass Capacitors" help us in this regard. A capacitor has a high
impedance to dc and a low impedance to voltage fluctuations. Putting a large (eg. 0.1F)
capacitor between the +5V and ground pins of your chips effectively short circuits the
fluctuations without affecting the steady dc voltage. We can think of bypass capacitors as
storing charge that can be used to quickly supply surge current needs.
When wiring supply bypass capacitors, we need to be careful!! Here’s why. When
you pick a large (0.1F – 10F ) capacitors, you are most probably using an “electrolytic
capacitor”. Electrolytic capacitors cannot handle positive and negative voltages. They are
usually marked quite clearly with plus "+" and/or minus "-" symbols to indicate their
preferred polarity. You can damage them by wiring them with reverse polarity. Usually,
the damage is accompanied with overheating and sometimes, a small explosion!!
C. The switches on the universal protoboard
The upper left part of the universal protoboard consists of an array of switches and two pushbuttons. They are described in detail below. It is suggested that you use the logic probe tool in
your toolbox to get to know the operation of these devices.
Switches 1,2,3 and 4: These are toggle switches that behave as follows.
B
COM
B
A
COM
A
When the switch is in the “A” position, the “COM” line is connected to “A”. When the
switch is in the “B” position, the “COM” line is connected to “B”. These switches can be
made to stay in either position for as long as we wish.
Switches 5,6, and 7 (“momentary toggle switches”): These switches are similar to the first
four switches except for the fact that they are spring loaded. They ordinarily stay in the “A”
position, as shown below.
A
B
COM
Normal Position
When operated, they do two things, as illustrated below:
 disconnect “COM” from “A” for as long as the switch is pressed;
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
connect “COM” to “B” for as long as the switch is pressed.
A
B
COM
When Pressed
Here are two ways to wire them up for use:
+5V
+5V
A
(not connected)
1K
A
B
1K
B
OUTPUT
= +5V in position A
0V in position B
OUTPUT
= +5V in position A
0V in position B
Switches 8, 9: These are push-button switches, and have only two connections “A” and “B”,
as indicated below.
A
A
B
B
Button not pressed means no connection
between A and B.
Button pressed means A and B are
connected as long as the button is held
pressed.
B
A
How you wire up a push-button switch makes a difference. You can wire up a push-button as
either a "high asserting" or "low asserting" switch as shown below.
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+5V
+5V
1K
Low-asserting output
(0V when pressed)
High-asserting output
(+5V when pressed)
1K
D. Connecting power to the prototyping board
Never apply power to your circuit until you have checked all connections carefully. In
particular, check for short-circuits. Shorts between power and ground will probably not
harm the power supply, but it could be disastrous to your circuit. Also check the polarity of
devices such as electrolytic capacitors. Many devices can be destroyed by improper
connection.
The upper right portion of the protoboard consists of terminals for attaching power leads
(they should be in your toolbox). Use the following color convention:
 Red: +5 volts
 Green/Black: Ground (0 volts)
 Purple: -12 volts
 Yellow: +12 volts
Step 3: Signoff and Cleanup
You must demonstrate your circuit to your TA and get it signed off.
You must cleanup after yourself. Specifically, please make sure that there are no pieces of
wires or plastic on the tables and floors. All pieces of wires are to be placed in the trash can.
Keep in mind that your TAs are instructed to not sign off on your activity unless you clean up
properly.
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