if-else Statements

if-else Statements

General syntax is as follows:

if( condition )     statement;

Consider the example
if( hold == 0 )     counter = counter + 1;

if( reset ) 
   counter = 0; else 
   counter = counter + 1;

if( reset ) 
begin 
   counter <= 0;
   over_flow <= 0; end
else if ( counter == 15 ) begin 
   counter <= 0;
   over_flow <= 1; end
else
begin
   counter <= counter + 1;
   over_flow <= 0; 
end 
  

if-else statements should be used inside initial or always blocks. 

module addsub (a, b, addnsub, result); input[7:0] a; input[7:0] b; input addnsub; output[8:0] result; reg[8:0] result; always @(a or b or addnsub) begin if (addnsub) result = a + b; else result = a - b; end endmodule

If addnsub is true( nonzero ), result will be a+b, otherwise result will be a-b.