libLCS - A Logic Circuit Simulation Library in C++

Let a and b be input signals to a 1-bit fulladder, and c the carry input. Let S be the sum output, and C the carry output. Then, the truth table for S and C is as shown below.

Truth table

a  |  b  |  c  |      S  |  C
---|-----|-----|---------|----
0  |  0  |  0  |      0  |  0
---|-----|-----|---------|----
0  |  0  |  1  |      1  |  0
---|-----|-----|---------|----
0  |  1  |  0  |      1  |  0
---|-----|-----|---------|----
0  |  1  |  1  |      0  |  1
---|-----|-----|---------|----
1  |  0  |  0  |      1  |  0
---|-----|-----|---------|----
1  |  0  |  1  |      0  |  1
---|-----|-----|---------|----
1  |  1  |  0  |      0  |  1
---|-----|-----|---------|----
1  |  1  |  1  |      1  |  1

The code to implement the above logic using conitnuous assignments 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> a, b, c, S, C;
        
    // Continuous assignment statements to generate
    // the sum and carry outputs. The template parameters
    // indicate the assignment delay. We have used 0 
    // delay here.
    S.cass<0>(a&~b&~c | ~a&b&~c | ~a&~b&c | a&b&c);
    C.cass<0>(a&b&~c | a&~b&c | ~a&b&c | a&b&c);

    ChangeMonitor<3> inputMonitor((c,b,a), "Input", DUMP_ON);
    ChangeMonitor<2> outputMonitor((S,C), "Sum", DUMP_ON);

    Tester<3> tester((c,b,a));

    Simulation::setStopTime(1000); 
    Simulation::start(); 

    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: 000
At time: 0,     Sum: 00
At time: 200,   Input: 001
At time: 200,   Sum: 01
At time: 300,   Input: 010
At time: 400,   Input: 011
At time: 400,   Sum: 10
At time: 500,   Input: 100
At time: 500,   Sum: 01
At time: 600,   Input: 101
At time: 600,   Sum: 10
At time: 700,   Input: 110
At time: 800,   Input: 111
At time: 800,   Sum: 11

- A Logic Circuit Simulation Library in C++

(libLCS Example) 1-bit Fulladder using continuous assignments

Truth table