VHDL Transparent Latch

  process (ENB, D)
  begin
    if ENB = '1' then
      Q <= D;
    end if;
  end process;

The value of Q will only change to Q if ENB is high. This is know as an incomplete assignment. Latch should no be used in FPGA because they need asynchronous feedback.

Reference

http://www.doulos.com

This blog post contains notes taken when working through the Doulos Pacemaker tutorial.   Any content copied from the tutorial has been reproduced with permission.  http://www.doulos.com.