March 3, 2003 page 1 S. Derenzo
Solutions for Midterm #1 - EECS 145M Spring 2003
1a The transparent latch has a digital input, and digital output, and a digital control input that
puts the circuit into transparent mode or hold mode. In transparent mode the output is equal
to the input. When the circuit is switched to hold mode the output is held at its current
value.
[5 points off if no hold mode]
1b The tri-state buffer has a digital input, and digital output, and a digital control input that
puts the circuit into transparent mode or tri-state mode. In transparent mode the output is
equal to the input. In tri-state mode the output is in a high-impedance state that neither
drives nor loads anything connected to it.
[5 points off if no high impedance mode]
2See Figures 3.16 and 3.17 on page 169 of the textbook
[2 points off for using an amplifier rather than a comparator]
[2 points off for not starting with all bits zero]
[5 points off for describing the tracking A/D converter]
3
•Acquire a computer with a digital I/O port and an internal clock
•Connect a pushbutton switch to one line of the digital input port and one line of the output
port to an amplifier and fast indicator light (like an LED)
•Write a computer program that detects a pushbutton, waits a random delay, prompts the
subject by turning on the light and measures the time until the pushbutton is pressed
•Select a large number of candidates representing group d (racecar drivers) and group p (jet
fighter pilots)
•After initial training and a good nights sleep, take as much reaction time data as possible,
allowing for rest periods
•Compute the average reaction times dp and , the standard deviation of the samples
ss
dp
and , and the standard errors of the mean ss
dp
and and compute Student’s t:
tdp dp
mm
dpdd pp
== -
+
=-
+
D
D
sss s s
22 2 2
//
•Look up the probability of exceeding this value or t by chance. If the probability is < 0.1%,
then the group with the lowest average has a faster reaction time.
[2 points off for only 10 measurements]
[5 points off if reaction time includes the random computer delay before the prompt]
[5 point off if Student’s t and probability not determined]
