Hallway Lighting

  1. Cross-Switch.

    Image

    We don't care about the stuations:

    A=0 B=0 X=0
    A=0 B=0 X=1
    A=1 B=1 X=0
    A=1 B=1 X=1
    

    because they never occur, so:

    A  B  X  QA  QB
    0  0  0  x   x
    0  0  1  x   x
    0  1  0  0   1
    0  1  1  1   0
    1  0  0  1   0
    1  0  1  0   1
    1  1  0  x   x
    1  1  1  x   x
    
  2. Cross as Left veksel (connect A and B): We only care about

    A=B=1
    

    situations, because A and B are always under voltage:

    A  B  X  QA  QB
    0  0  0  x   x
    0  0  1  x   x
    0  1  0  x   x
    0  1  1  x   x
    1  0  0  x   x
    1  0  1  x   x
    1  1  0  1   0
    1  1  1  0   1
    

    This (A=B=1) situations were "don't care" for the Cross-Switch, so we may combine them into the new ComboCross:

    A  B  X  QA  QB
    0  0  0  x   x
    0  0  1  x   x
    0  1  0  0   1
    0  1  1  1   0
    1  0  0  1   0
    1  0  1  0   1
    1  1  0  1   0
    1  1  1  0   1
    

    Autogenerated circuit: Logisim -> Combinational Analysis -> Table

    [ Build Circuit ]
    
    Circuit name: X
    [v] Use 2 Inputs Gates Only, 
    [ ] Use NAND Gates Only
    
    [ OK ]
    

    Image

  3. ComboCross as Right veksel (use only QA or QB):

    The ComboCross truth table perfectly satisfies our needs for the "Right veksel".

  4. Logisim simulation for 6 nodes "Hallway lighting":

    Image

    download solution here. Use "Project -> Analyze circuit" to recover the Truth Table (don't cares would be lost and replaced with actual values for auto-generated subcircuit X)

    http://kirill.tpt.edu.ee/src/vex6.circ