ELE 391 Digital Electronics Laboratory Fall Semester 2013 Experiment #4

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Nov 15, 2013 (3 years and 6 months ago)

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ELE 391 Digital Electronics Laboratory

Fall Semester 201
3

Experiment #
4


MSI components and
Display

Systems


Implementation due Date:



Final Report due Date

:



Registers

and Counters


Repeat the experiment to build, test, and demonstrate four
D
-
flip
-
flops from a bussed signal.
Use the four slide switches for the D inputs and four LEDs for the Q outputs. Use a push
-
button
as the system clock for all the flip
-
flops. This circuit has the complexity to make it a circuit of
“Medium Scale Integrat
ion”, MSI. An AND Gate, for example
,

would be called SSI
; “Small
Scale Integration”
. Higher levels of integration are called LSI, VLSI, and ULSI. The name of
this MSI component is a Register. This is a 4
-
bit register.


Remake the circuit using VHDL so

it implements another MSI component called a shift register.
Demonstrate a 4
-
bit Shift Register. Use the same fou
r LEDs, push
-
button clock. N
otice only
one slide switch will be needed

because a shift register has only one input; regardless of how big
i
t is
.


Now add an enable signal to shift register and clock it with the 50MHz clock. Demonstrate the
circuit.


Fix the shift register with the pulse synchronizer circuit and demonstrate it.


The final MSI component will be the
4
-
bit
counter. You have already made this component,
however, this time use the Math Libraries. Demonstrate the
counter clocked at 50MHz,
fixed to
count

one number at a time.


Timer counters


The next part of this experiment is to build a counter that will del
ay for a specific amount of
time. The counter will be clocked with the 50MHz clock.
Each lab bench will be assigned a
different amount of time. The number listed is the amount of pulses that should be produced
each second. This type of counter is calle
d a Modulo
-
n counter, were you have to decide the
value of n. Build
,

test
,

and demonstrate a Mod
-
n counter for the specific time assigned to you.

To observe the output on an oscilloscope, assign the pin to the 6
-
pin header shown to you in
class.


Once you have the correct number of pulses produced by the counter, add the circuitry to make a
square wave output which changes its logic value each time a pulse occurs. Measure the
frequency of this square wave. Demonstrate the output
on an oscilloscop
e
to the instructor.


Build a digital controlled oscillator, DCO.
Use the four slide switches on the demo board to
control the frequency output from the DCO.
Assume the time increment assigned to your lab
bench has a value, T. The waveforms shown below
depict how your DCO should work.

Have
the output of the DCO drive one of the on
-
board LEDs, as well as the oscilloscope.
Demonstrate
your circuit to the instructor.

How does the brightness of the LED vary as you change the
frequency?




Build a pulse w
idth modulation unit, PWM. Again, use the four slide switches on the
demo board to control the pulse width of the PWM. A PWM unit produces a constant frequency
output. The waveforms shown below depict how your
PWM

should work.
Again, drive one of
the
on
-
board LEDs

with the output of the PWM unit
, as well as the oscilloscope. Demonstrate
your circuit to the instructor.
Now, h
ow does the brightness of the LED vary as you change the
width of the pulse
?






Fun with LED displays



Design circuits
for y
our FPGA
to display
each of
the following patterns on a graphic
LED display
.
To form the pattern, o
nly one LED is
turned on

at a time. The illuminated
LED
appears to “move” around the display creating the pattern. In order to control the movement, use
t
he rotary switch mounted on your FPGA board. As you turn the switch clockwise, the
illuminated LED will move around the pattern one direction. When you stop turning the switch,
the LED movement should stop. And if you turn the rotary switch in the other

direction, the
pattern will progress backwards.
If necessary, you may add extra circuitry outside the FPGA on
your breadboard in order to “drive” the LEDs in your display. Demonstrate one of the patterns,
chosen by the instructor, to the instructor.


On
e row






Every row








Every row both directions




Around the outside edge


















Pulses per second:


Lab Bench


1, 2400

Lab Bench


2, 19200

Lab Bench


3, 921600

Lab Bench


4, 38400

Lab Bench


5, 115200

Lab Bench


6, 4800

Lab Bench


7, 230400

Lab Bench


8, 9600

Lab Bench


9, 57600

Lab Bench


10, 460800