I'm trying to use the HTG-FMC-RS485 board which has multiple LTC2865's on a single card connected to an FMC connector to allow an FPGA interface. The problem is, not all FMC pins on my FPGA board are routed, meaning I have several LTC2865's that are powered, but have all TTL pins floating with no pull-ups or pull-downs.
Obviously I can't use the floating parts, but I'm wondering if this will cause some bad side effects?. Are there internal pull-ups/pull-downs that will keep the device in a quiet state, or will the floating pins cause excessive switching, power draw, or noise? The RS-485 differential lines themselves do have a pull up/down and termination resistors, just nothing on the RO,DI,RE,DE, or SLO pins.