Silicon, Circuits, and the Digital Revolution

Selected Questions from 1999 Final Exam

6. (2 pts.)
At a SETI station (Search for Extra-Terrestrial Intelligence), the following binary signal repeatedly appears in the radio-frequency region of the electromagnetic spectrum. An alert computer operator notices that the message appears to be in ASCII. What does the message say? -- translate! 

0111  0011    0110  0101    0110  1100    0111  0101
    0101  0010     0011  0011     0011  0000     0011  0001

__ __ __ __ __ __ __ __

Encode the following message for transmission in an intelligible form to the remote source:

CMOS2! 

.... ....    .... ....    .... ....    .... ....    .... ....    .... ....

7. (2 pts.)

Complete the truth table below for the above gate combination.

A B C D E
0 0     1
0 1     0
1 0     0
1 1     0

What two-input gate should be used in the rectangular box (??) above to generate the desired truth table, where the output E is true when A and B are both false?

8. (3 pts.)
Construct the truth table for the combination of transistor switches shown below by indicating the on/off state of each transistor and the final output state for the eight different input possibilities.
(Remember that n-channel MOSFETs are turned on by application of a positive voltage (HI); p-channel MOSFETs by application of ground (LO).

A B C 1 2 3 4 5 6 D
      on/off  
LO LO LO              
LO LO HI              
LO HI LO              
LO HI HI              
HI LO LO              
HI LO HI              
HI HI LO              
HI HI HI              

Which 3-input logic gate does the circuit represent?

 

SCEN103 Comments, suggestions, or requests to ghw@udel.edu.
"http://www.physics.udel.edu/~watson/scen103/colloq2000/selections1.html"
Last updated May15, 2000.
© George Watson, Univ. of Delaware, 2000.