Differences-between-macros-and-parameters
| Macros | Parameters |
|---|---|
| macros are replaceable | parameters are like variables |
| macros works in pre-compilation state | parameters works in Elaboration state |
| syntax : `define macro_name value | syntax : parameter parameter_name=value |
| We can use `define in any file | we can use parameter within the file |
| we can’t give datatypes in macros | we can use and change datatype in parameters |
| Macros can have multiple lines | multiple lines cannot be possible here because parameter is just like declaring variables |
| We can give value for a macro in command line | parameters value can’t be changed in command line |
Execution stage of macros and parameters#
Parameters used in macros#
parameter data = 5; // data will be replaced by value 5 in Elaboration
`define DATA data // in pre-compilation `DATA will be replaced with data
module tb();
int a,b;
initial begin
$display("DATA=%0d",`DATA);
b= `DATA + 2;
$display(" b=%0d",b);
end
endmodule
In the above code the parameter value of data =5 is used in the macro `DATA
Macros used in parameters#
`define DATA 25
parameter data = `DATA;
module tb();
int a,b;
initial begin
$display("data=%0d",data); // in pre-compilation `DATA will be replaced with 25.
$display("DATA=%0d",`DATA); // data will be replaced by value 25 in Elaboration
a = data +5;
b= `DATA + 2;
$display("a=%0d b=%0d",a,b);
end
endmodule
In the above code the macro value of `DATA 25 is used in the parameter data.
Macros(`define) can be used in command line
-timescale 1ns/1ns +define+name=20
`define name 10
module hi;
int a;
initial begin
$display("[%0t] a = %0d",$time,a);
#1 a = `name;
$display("[%0t] a = %0d",$time,a);
end
endmodule
We can give inputs to macros in command line interface using -timescale 1ns/1ns +define+name=20 in compile options .