Question

I am writing a simple vga controller and I find myself repeating the same pattern again and again. How I can avoid this.

red_out <= zero(x-106,y-63)&zero(x-106,y-63)&zero(x-106,y63)&zero(x-106,y-63);
green_out <= zero(x-106,y-63)&zero(x-106,y-63)&zero(x-106,y-63)&zero(x-106,y-63);
blue_out <= zero(x-106,y-63)&zero(x-106,y-63)&zero(x-106,y-63)&zero(x-106,y-63);

Maybe a command that will help me avoid the repetition?

Answer 1

• To replace the expression zero(x-106,y-63)&zero(x-106,y-63)&zero(x-106,y63)&zero(x-106,y-63), use a function. The code would then look something like red_out<=f(zero, x, y); etc.
• To replace all three statements, use a procedure. The code would then look something like p(red_out, green_out, blue_out, zero, x, y).

Check http://www.csee.umbc.edu/portal/help/VHDL/design.html for the syntax.