CPE 201/EE 236 Lab 9
(UNR/2005 Spring)
Sequence Detector
Introduction (5 points):
Flip flops as memory devices can be used to design sequence detectors. When
a predefined sequence of inputs (on/off, represented as a binary
number, e.g., 101) is fed into the sequence detector, there will be
an output from the detector (in a common case, output becomes "1" from "0").
Particular attention should be paid to the description of specific problem
in question. For example, when talking about designing a circuit that detects
a sequence of "101", do we expect the output to be "00100" or "00101" under
the input sequence of "10101"?
Objective (5 points):
To design a sequential circuit to detect the sequence 1101.
Procedure (80 points):
1. Design a sequence detector that outputs "1" when it detects a sequence
of "1101" with D flip flops. Including the following in your lab reports
(40 points):
- State and output table
- Transition (coded state) and output table
- Excitation (flip flop's inputs) table
- Excitation maps (K maps)
- Simplified logic expressions for the flip flop inputs
- Logic circuit (with D flip flops with active-low preset and
active-low clear inputs, NOT, and 2/3/4-input NAND gates)
2. Implement the designed circuit on the breadboard and show the results
to TA (40 points) using:
- 7474 (D flip flop with active-low preset and active-low
clear inputs)
- 7410 (3 -input NAND)
- 7420 (4-input NAND)
- 7400 (2-input NAND)
- 7404 (NOT)
Conclusion (5 points):