Question

What type of the combinational circuit is described by the following VHDL process? process (A,B)    begin    if (A = '0' and B = '1') OR (A='1' AND B='0') then    Y <= '1';    else    Y <= '0';    end if;    end process; 1. XOR gate 2. XNOR gate 3. 2-to-1 MUX 4. half adder

Answer 1

VHDL Code

process (A,B)
   begin
   if (A = '0' and B = '1') OR (A='1' AND B='0') then
   Y <= '1';
   else
   Y <= '0';
   end if;
   end process;

From above code we conclude this truth table:

A	B	Y
0	0	0
0	1	1
1	0	1
1	1	1

1. XOR gate

here is the truth table :

In above VHDL code , when the input A=1 , B=0 the output Y is high i.e 1 and also when the input A=0 , B=1 the output Y is high(1) , similarly in the xor gate truth table same thing happen

2. Xnor Gate

Here the truth table:

The above table doesnot match with VHDL code truth table

3. 2-to-1 MUX

Multiplexer does not behave as as given in VHDL Code , it is used to select input

4. Half adder

Half adder contains two output one is carry and one is sum but in VHDL code only one output is there.

so here is answer of your question:

The above VHDL code descibes XOR Gate circuit .