Circuitry is provided to individually configure each I/O of an integrated
circuit to be compatible with a different LVTTL I/O standards. This can be done
with only one I/O supply voltage, where that voltage is the highest of the I/O
voltages needed in a particular application. The circuitry operates by regulating
the output voltage of the I/O cell so that it is above the VOH and below the maximum
VIH for the LVTTL standard for which it will comply with. Since each I/O cell is
individually configurable, any I/O can drive out to any LVTTL specification.