Add comment about sim_ddr size.

libraries/io/ddr/tb/vhdl/tb_io_ddr.vhd

@@ -69,7 +69,9 @@ ARCHITECTURE str of tb_io_ddr IS
 
   -- Select DDR3 or DDR4 dependent on the technology and sim model
   CONSTANT c_mem_ddr                  : t_c_tech_ddr := func_tech_sel_ddr(g_technology, g_tech_ddr3, g_tech_ddr4);
-  CONSTANT c_sim_ddr                  : t_c_tech_ddr := func_tech_sel_ddr(g_technology, c_tech_ddr3_sim_16k, c_tech_ddr4_sim_4k);
+
+  -- Need to use >= c_tech_ddr4_sim_16k for g_block_len = 2500 in tb_tb_io_ddr
+  CONSTANT c_sim_ddr                  : t_c_tech_ddr := func_tech_sel_ddr(g_technology, c_tech_ddr3_sim_16k, c_tech_ddr4_sim_16k);
   CONSTANT c_tech_ddr                 : t_c_tech_ddr := func_tech_sel_ddr(g_sim_model, c_sim_ddr, c_mem_ddr);
   
   CONSTANT c_exp_gigabytes            : INTEGER := func_tech_ddr_module_gigabytes(c_tech_ddr);