# Laboratory 1 Digital Systems

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15 Νοε 2013 (πριν από 4 χρόνια και 7 μήνες)

102 εμφανίσεις

University of British Columbia

Electrical and Computer Engineering

EECE
259

Laboratory 1

Digital Systems

PJ Davies

Rational
: The purpose of this lab is
:
-

1.

To
develop

the
student’s

ability

to think in terms of turning a requi
rement for a
digital system into a set of logic gates that will realise those requirements.

2.

To become familiar with the idea of simulating a logic circuit using the
Electronics Workbench tool supplied with the course text and available in the Lab

Outline
:

A control system involved in the manufacturing of ‘
widgets’

has 4 inputs
labelled
A

D

and two outputs
Out1

and
Out2
. You
r

task is to design a circuit using
AND, OR and NOT gates to implement the following
two simultaneous
requirements
.

Out1 is
False

(i
.e. logic 0) under the following conditions:

A =
True
, B =
False
, C =
True
, D =
T
rue
. For all other conditions, O
ut1 is
True

Out2 is
True

(i.e. logic 1)
under the following conditions:

Inputs A or D are
True
. For all other conditions, Out2

is
False
.

Pro
cedure

Step 1
: Design on paper, the logic required to implement these two outputs in terms of
the inputs A,

B,

C and D

and basic AND,

OR, NOT gates
, i.e. draw the circuit in terms of
gates connected together and to inputs and outputs using wires
.

Step 2
:

Your instructor will give you a
Multisim
file
(a copy is also on the 259 web site
in the labs section)
which you should copy to your own
computers folder/
directory.
Open
this file with the

National Instruments (NI) Multisim

software
.

You should see tha
t it has four inputs
A
-
D

and two outputs
Out1

and Out
2
. By pressing
the keys
A

D

on
your

PC keyboard, you can change the state of the
‘virtual’
inputs
A
-
D
,
connecting them either to 5 volts (
i.e. a
logic 1

or
true
) or ground/0v (
a
logic 0

or
false
)

see b
elow

Step3
: Using the ‘place
-
>component

in
NI Multisim software, chose component
s

from
TTL Group

/
74
LS
xx

series of devices and place them onto your circuit

see
below.
(Hint:
the
74
LS
04
N

component
contains 6 NOT gates,
the
74
LS
08
N

contains 4
,

t
wo input AND gates and

the

74
LS
32
N

contains 4
,

two input OR gates)
.

Step 4
:
Start the simulation by clicking on the simulation switch

Check your design gives the correct results (i.e. it meets the specification of the problems
defined earlier in
the ‘Outline’

by toggling the switches and observing the output lamps
.

Step 5
:
Stop

wise it will use huge PC resources if it runs for a long
time). Now r
ONLY

a combination of
NOT

gates

plus

NAND

gates (a Na
nd gate is an And gate with an inverter wired to the output

the
74
LS
00
N
component

contains 4
,

two input Nand gates). Change your circuit within
NI Multisim

and verify that the requirements are still met
.

Note you will have to think about how to
create an

OR gate from a NAND

plus NOT gates

(the theory was covered in lecture 1)

7404

Hex Inverters

7432

7408

7411

Triple 3

input AND

7421

Dual 4 input And

7400

7410

Triple 3 input NAND

7402