System for coupling programmable logic device to external circuitry which selects a logic standard and uses buffers to modify output and input signals accordingly

A programmable input/output device for coupling a programmable logic device (PLD) to external circuitry, the input/output device comprising:

• means for coupling the input/output device to the external circuitry;
• means for receiving output signals from the PLD and for modifying the output signals in accordance with a selected logic standard, the means for receiving providing the modified output signals to the means for coupling;
• means for modifying input signals received from the means for receiving and the means for coupling in accordance with the selected logic standard, the means for modifying providing the modified input signals to the PLD;
• and
• means for selecting the selected logic standard from a plurality of logic standards.

A method for providing a programmable logic device (PLD) with the capability of being selectively coupled to external circuitry which operates in accordance with a selected one of a plurality of logic standards, the methods comprising the steps of:

• programmably selecting the selected one of a plurality of logic standards;
• modifying output signals from the PLD in accordance with the selected logic standard such that high PLD signals correspond to high signals of the selected standard and low PLD signals correspond to low signal of the selected standard;
• receiving input signals from an external interface;
• and
• modifying the input signals in accordance with the selected logic standard such that high input signals are converted to high PLD signals and low input signals are converted to low PLD signals.