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Final Quiz for Microprocessor Application | EEL 4744, Quizzes of Microprocessors

University of Florida (UF)Microprocessors

Material Type: Quiz; Class: MICROPROCESSOR APPLIC; Subject: ENGINEERING: ELECTRICAL; University: University of Florida; Term: Unknown 1989;

Typology: Quizzes

Pre 2010

Uploaded on 09/17/2009

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Page 1 of 3 Page Total Pts. =
EEL 4744C – Dr. Gugel Last Name, First Name_________________________________________
Fall Semester 2004
Final Quiz SS#____________________________________
• Open book and open notes, 90-minute maximum examination to be done in pencil.
• Calculators are permitted. No Laptops or PDAs.
Page 1 30 points _________________
Page 2 35 points _________________
Page 3 35 points _________________ TOTAL _________________out of 100
Part A. Generic A/D & D/A Questions
You are given the following A/D converter specifications: 10 bits, UNSIGNED, Vref_high = +3.3V, Vref_low = 0V.
1. What is the resolution of the A/D converter? (4 pts.)
resolution = Vspan / 2N = 3.3V / 210 = 3.22 mV
2. What is the theoretical dynamic range of the 10 bit A/D converter in dBs? (4 pts.)
dynamic range in dBs = 20 log (Vspan / resolution) = 20 log (2N) = 60 dBs
or 6 dBs/bit x 10 bits = 60 dBs
3. Our input signal has frequencies in the bandwidth of 0-10 KHz and we are only interested in frequencies from 0-3 KHz. With a
sampling rate set at 10 KHz, what should be done to minimize aliasing? (4 pts.)
LPF at 5 KHz or LPF at 3 KHz
4. What Hex digital value is expected when we sample a voltage at 1.75312V? (5 pts.)
1.75312V / ? ˜ 544 = $220
5. To be within 1% accuracy or better, what must the span of our input signal be? Use less than, greater than or equal to signs
where appropriate. (5 pts.)
accuracy = resolution / Vinput_span * 100 % = 3.22mV / Vinput_span * 100% <= 1%
Vinput_span > = 32 2mV or 0.322 V
6. If a student hooks up a microphone and preamplifier to the A/D and finds that there are 10 mV of noise on the signal coming out
of the preamplifier, what is the new expected dynamic range in dBs? (4 pts.)
dynamic range in dBs = 20 log (Vspan / Vnoise) = 20 log (3.3v / 10mV) = 50.4 dBs
7. How many bits are corrupted effectively by this noise above in #6? (4 pts.)
60 dBs – 50.4 dBs = 9.6 dBs corrupted, or 2 bits
$3ff
$200
3.3v
1.65v
1.75312v
$0 0v
pf3

Partial preview of the text

Download Final Quiz for Microprocessor Application | EEL 4744 and more Quizzes Microprocessors in PDF only on Docsity!

EEL 4744C – Dr. Gugel Last Name , First Name_________________________________________

Fall Semester 2004

Final Quiz SS#____________________________________

• Open book and open notes, 90-minute maximum examination to be done in pencil.

• Calculators are permitted. No Laptops or PDAs.

Page 1 30 points _________________

Page 2 35 points _________________

Page 3 35 points _________________ TOTAL _________________out of 100

Part A. Generic A/D & D/A Questions

You are given the following A/D converter specifications: 10 bits, UNSIGNED , Vref_high = +3.3V , Vref_low = 0V.

  1. What is the resolution of the A/D converter? (4 pts.)

resolution = Vspan / 2N^ = 3.3V / 2^10 = 3.22 mV

  1. What is the theoretical dynamic range of the 10 bit A/D converter in dBs? (4 pts.)

dynamic range in dBs = 20 log (Vspan / resolution) = 20 log (

N

) = 60 dBs

or 6 dBs/bit x 10 bits = 60 dBs

  1. Our input signal has frequencies in the bandwidth of 0-10 KHz and we are only interested in frequencies from 0-3 KHz. With a sampling rate set at 10 KHz , what should be done to minimize aliasing? (4 pts.)

LPF at 5 KHz or LPF at 3 KHz

  1. What Hex digital value is expected when we sample a voltage at 1.75312V? (5 pts.)

1.75312V /? ˜ 544 = $

  1. To be within 1% accuracy or better, what must the span of our input signal be? Use less than, greater than or equal to signs where appropriate. (5 pts.)

accuracy = resolution / Vinput_span * 100 % = 3.22mV / Vinput_span * 100% <= 1%

Vinput_span > = 32 2mV or 0.322 V

  1. If a student hooks up a microphone and preamplifier to the A/D and finds that there are 10 mV of noise on the signal coming out of the preamplifier, what is the new expected dynamic range in dBs? (4 pts.)

dynamic range in dBs = 20 log (Vspan / Vnoise) = 20 log (3.3v / 10mV) = 50.4 dBs

  1. How many bits are corrupted effectively by this noise above in #6? (4 pts.)

60 dBs – 50.4 dBs = 9.6 dBs corrupted, or 2 bits

$3ff

$

3.3v

1.65v

1.75312v

0v $

You are now given a 10 bit , UNSIGNED D/A with Vref high tied to +5.5V and Vref low tied to -5.5V , answer the following:

  1. What is the expected voltage output for $300? (5 pts.)

$300 = 768, -5.5 V + 768 x ( 11V / 2

10

  1. If the 10 bit, UNSIGNED D/A is replaced with a 10 bit , SIGNED D/A with the same Vref high +5.5V and Vref low -5.5V , what is the expected voltage output for $300? (5 pts.)

$300 = -256, -256 x (11V / 2

10

or count from bottom $300 - $200 = $100 = 256

-5.5V + 256 x (11V / 2

10

Part B. 68HC12 Output Compare & General Timings

We would like to use an OC3 interrupt on the 68HC12 to play out a waveform stored in memory at $A00. Assume that you have an 8 bit D/A attached to a latch at $9000. Vref high is tied to 5V and Vref low is tied to 0V. The waveform that we would like to play out is a sine wave with a 2.5V DC offset comprised of 64 samples and it has a peak to peak voltage (span) equal to 5V.

  1. If you have an external crystal oscillator equal to 8 MHz , what must the frequency of the OC3 interrupt be such that the frequency of the sine wave is 500 Hz? Assume TCNT will be run at its fastest rate possible. (4 pts.)

500 Hz * 64 samples = 32 KHz

  1. Assuming again an 8 MHz external crystal as in #1, what value must be added each time to TC3 in the ISR to create a 500 Hz sine wave? Assume TCNT will be run at its fastest rate possible. (4 pts.)

EClk = 4 MHz, 4 MHz / 32 KHz = 125

  1. What is the slowest frequency sine wave we can generate in Hz without using the TCNT overflow interrupt or TCNT overflow flag? Assume 8 MHz external crystal and that TCNT will be slowed down to its slowest rate possible. (6 pts.)

PR2:PR0 = 101 ‡ prescale factor = 32

4 MHz / 32 = 125 KHz (slowest TCNT frequency)

125 KHz / 2^16 = 1.90735 Hz (frequency of OC, at each OC send the next value)

1.90735 Hz / 64 = 0.0298 Hz (frequency of the sine wave)

  1. Assuming that the OC3 interrupt service routine will be placed in EPROM , show the code below that is necessary to direct the interrupt vector to the interrupt handler’s label “TC3_Int_Handler”. (5 pts.)

ORG $FFE

DC.W TC3_Int_Handler

  1. What are the first three values that should be stored in waveform memory from $A00-$A02? (6 pts.)

output (in hex) = $80 + $7F sin(2PI x N / 64)

output (in decimal) = 128 + 127 sin(2PI x N / 64)

$A00 = $80 or 128 (N=0) $A01 = $8C or 140 (N=1) $A02 = $98 or 153 (N=2)

$3ff

$

5.5v

0v

-5.5v $

  • $300?

$1ff

$

5.5v

0v

-5.5v $

-$300?