HiI want to ask. In every manual is written that DQ pins are suitable for DDR interface but have they any hardware difference from other IO pins at same bank ? In Cyclone devices are all DDR registers implemented at LE ports have no hardware for it and in datasheet I cant find any description of their difference. Is here any real hardware reason to have some pins suitable for DQ and some not ? Where I can find info about it ? Is it something that is not written in Handbook and Datasheet or have it other reason ?
Check the EMIF handbook:https://www.altera.com/support/literature/lit-external-memory-interface.html All devices have pins that are optimized for use as memory interfaces. You can see these highlighted in the Pin Planner by selecting an option from the View menu for external memory. Each set of DQ pins is associated with one or more DQS pins. The pin planner highlights these groups in different colors and amounts of DQ pins depending on the width you select (x4, x8/x9, etc.). You can use other pins with the soft IP, but they are not optimized for EMIF use. For hard IP (Cyclone V has it), you have to use specific pins.