Verilog Constant Numbers

[fcfusion]

Hi everyone

I have a silly question but I haven't found the solution anywhere else, so I hope you guys can help me.

How can some one implement a constant number without having to waste registers with it? For example, I want to add a variable "var" with a constant "c":

reg [15:0] var;

sum=var+c;


Is there a way to define the constant "c" through a "wire" with bits connected to VCC or GND, depending on the value. Usually I can do this on schematic when using Xilinx ISE but I dont know how to do it in Verilog.

Thanks

 

[mrflibble]

Use a parameter?

reg [15:0] var;

parameter c=123;
sum=var+c;

 

[permute]

or in verilog2001, a localparam.

verilog offers 3 "constant" types:
`define MY_CONST 123
This replaces `MY_CONST with 123. It generally isn't preferred, as the value of `MY_CONST can persist between files based on compile order. This can lead to unexpected behavior.

parameter MY_CONST = 123;
This creates a constant similar to VHDL's generic. This value can be overridden at instantiation using #(.MY_CONST(456))

localparam MY_CONST = 123;
This creates a constant that cannot be changed. Using localparam is useful because it makes it clear that the parameter is not meant to be changed at instantiation.

 

[fcfusion]

or in verilog2001, a localparam.

verilog offers 3 "constant" types:
`define MY_CONST 123
This replaces `MY_CONST with 123. It generally isn't preferred, as the value of `MY_CONST can persist between files based on compile order. This can lead to unexpected behavior.

parameter MY_CONST = 123;
This creates a constant similar to VHDL's generic. This value can be overridden at instantiation using #(.MY_CONST(456))

localparam MY_CONST = 123;
This creates a constant that cannot be changed. Using localparam is useful because it makes it clear that the parameter is not meant to be changed at instantiation.

Very usefull thanks

Now I have another question: Is it possible to initialize a constant as a vector, so that I can store several coefficients in one single vector instead of separate constants?