2 Replies Latest reply on Oct 26, 2011 11:16 AM by david.wang

    Which IO standard (LVTTL/LVCMOS/3.3/3.0/2.5) to choose when connecting an FPGA with FX2LP? Both are powered at 3.3V

    david.wang

      I am connecting a Cyclone III FPGA directly with FX2LP, but I am not sure which IO standard to choose on the FPGA side?  The options in Altera Quartus II are: LVTTL-3.3V, LVCMOS-3.3V,  LVTTL-3.0V, LVCMOS-3.0V, 2.5V, etc.. The IO banks of the FPGA are powered at 3.3V using the same power source as the FX2LP.

         

      I have a FPGA program which seems to run correctly using the default 2.5V IO Standard. However, if I change the IO standard to LVCMOS-3.3V or LVTTL-3.3V (which should be the correct choice),  the program does not seem to work.

         

      Thanks for any suggestion in advance.