Can anyone please help me to understand what’s going on in sign_extend.v

,

this macro is initiated in the cic_decim.v

sign_extend #(bw,bw+maxbitgain)

ext_input (.in(signal_in),.out(signal_in_ext));

when i opened the macro i couldn’t understand it’s function

// Sign extension “macro”

// bits_out should be greater than bits_in

module sign_extend (in,out);

parameter bits_in=0; // FIXME Quartus insists on a default

parameter bits_out=0;

input [bits_in-1:0] in;

output [bits_out-1:0] out;

assign out = {{(bits_out-bits_in){in[bits_in-1]}},in};

endmodule

Thanks in advance.