AHDL Function Prototype
FUNCTION ALT_IOBUF (i, oe, )
   WITH (IO_STANDARD, CURRENT_STRENGTH, SLOW_SLEW_RATE, LOCATION, ENABLE_BUS_HOLD,
      WEAK_PULL_UP_RESISTOR, TERMINATION);
   RETURNS (io, o );
FUNCTION ALT_IOBUF (i, oe, )
   WITH (IO_STANDARD, CURRENT_STRENGTH, SLOW_SLEW_RATE, LOCATION, ENABLE_BUS_HOLD,
      WEAK_PULL_UP_RESISTOR, TERMINATION);
   RETURNS (io, o );