- A Logic Circuit Simulation Library in C++

(libLCS Example) 2-to-1 Mux using continuous assignment

The aim of this example it build and simulate a 2-to-1 multiplexer using continuous assignments. The block diagram of the circuit we intend to build is as follows.


The the boolean function for out is:

 out = a1'.a2.sel + a1.a2'.sel' + a1.a2.sel' + a1.a2.sel 

The code to implement the above logic equation is as follows.

#include <lcs/bus.h>
#include <lcs/tester.h>
#include <lcs/simul.h>
#include <lcs/changeMonitor.h>

using namespace lcs;

int main(void)
    Bus<1> a1, a2, sel, out;
    out.cass<0>(~a1&a2&sel | a1&~a2&~sel | a1&a2&~sel | a1&a2&sel);

    ChangeMonitor<2> inputMonitor((a2,a1), "Input", DUMP_ON);
    ChangeMonitor<1> selectMonitor(sel, "Select", DUMP_ON);
    ChangeMonitor<1> outputMonitor(out, "Output", DUMP_ON);

    Tester<3> tester((a1,a2,sel));


    return 0;

The output when the above program is compiled and run is as below. See this for information on interpreting the output.

At time: 0,     Input: 00
At time: 0,     Select: 0
At time: 0,     Output: 0
At time: 200,   Input: 10
At time: 200,   Output: 1
At time: 300,   Input: 01
At time: 300,   Output: 0
At time: 400,   Input: 11
At time: 400,   Output: 1
At time: 500,   Input: 00
At time: 500,   Select: 1
At time: 500,   Output: 0
At time: 600,   Input: 10
At time: 700,   Input: 01
At time: 700,   Output: 1
At time: 800,   Input: 11

Bewlow is the screenshot of the gtkwave plot of the generated VCD file.


Copyright © 2006, 2007 Siva Chandra