Description

My code contains the following:

   ladder2: for i in 0 to 14 generate begin
  process (clk, rst) begin 
   if rst = '1' then
--     xin(i+1,3) <= "00" & x"000";
--     xin(i+1,2) <= "00" & x"000";
--     xin(i+1,1) <= "00" & x"000";
--     xin(i+1,0) <= "00" & x"000";
    LADD:
    for j in 0 to 3 loop
     xin(i+1,j) <= "00" & x"000";
    end loop;
    

The commented out lines work, however the loop below them executes but does not behave as expected.

Solution

Below is an alternative method to achieve this behavior:

ladder2: for i in 0 to 14 generate begin
  gen1:  for j in 0 to 3 generate begin
     process (clk, rst) begin           
        if rst = '1' then
             xin(i+1,j) <= "00" & x"000";
        elsif rising_edge(clk) then
             xin(i+1,?) <= xin(i,j);
        end if;
     end process;   
  end generate;
end generate;