Technique of fabricating integrated circuits having interfaces compatible with different operating voltage conditions

A method of fabricating an integrated circuit comprising:

• providing an integrated circuit core compatible with a first supply voltage;
• providing a first interface for the integrated circuit designed to handle input signals from external circuits compatible with a second supply voltage and generate output signals for external circuits compatible with the first supply voltage;
• providing a second interface for the integrated circuit designed to handle input signals from external circuits compatible with the second supply voltage and generate output signals for external circuits compatible with the second supply voltage;
• and
• selectively coupling the first interface or second interface to the core,
• wherein the core and selected interface of the integrated circuit are coupled to one external positive supply level, and when the first interface is selected, the external positive power supply level is the first supply voltage and when the second interface is selected, the external positive supply level is the second supply voltage.

A method of fabricating a programmable logic integrated circuit comprising:

• providing an integrated circuit core having programmable logic and compatible with a first supply voltage;
• providing a first interface for the integrated circuit designed to handle input signals from external circuits compatible with the first supply voltage and generate output signals for external circuits compatible with the first supply voltage;
• providing a second interface for the integrated circuit designed to handle input signals from external circuits compatible with a second supply voltage and generate output signals for external circuits compatible with the first supply voltage;
• providing a third interface for the integrated circuit designed to handle input signals from external circuits compatible with the second supply voltage and generate output signals for external circuits compatible with the second supply voltage;
• and
• selectively coupling the first interface, second interface, or third interface to the core, wherein the core and selected interface of the integrated circuit are coupled to one external positive supply level, and when the first interface or second interface is selected, the external positive power supply level is the first supply voltage and when the third interface is selected, the external positive supply level is the second supply voltage.

A method of fabricating a programmable logic integrated circuit comprising:

• providing a core of the integrated circuit having programmable logic and compatible with a first supply;
• providing a plurality of interface circuits for interfacing the core to external circuits;
• and
• selecting one of said plurality of interface circuits, wherein the core and selected interface circuits are coupled to one external positive supply level.

A programmable logic integrated circuit comprising:

• an integrated circuit core compatible with a first supply voltage;
• a first interface designed to handle input signals from external circuits compatible with the first supply voltage and generate output signals for external circuits compatible with the first supply voltage;
• a second interface designed to handle input signals from external circuits compatible with a second supply voltage and generate output signals for external circuits compatible with the second supply voltage;
• and
• code that selectively couples the first interface or second interface to the core,
• such that the core and selected interface are coupled to one external positive supply.

A digital system comprising:

• a programmable logic integrated circuit comprising:
• an integrated circuit core compatible with a first supply voltage;
• a first interface designed to handle input signals from external circuits compatible with the first supply voltage and generate output signals for external circuits compatible with the first supply voltage;
• a second interface designed to handle input signals from external circuits compatible with a second supply voltage and generate output signals for external circuits compatible with the second supply voltage;
• and
• a configuration integrated circuit coupled to the programmable logic integrated circuit and storing configuration code, the configuration code comprising:
• code for selectively coupling the first interface or second interface to the core,
• such that the core and selected interface are coupled to one external positive supply level.

A computer program embodied on a computer readable media for use in manufacturing integrated circuits, the computer program comprising:

• code that defines an integrated circuit core compatible with a first supply voltage;
• code that defines a first interface designed to handle input signals from external circuits compatible with the first supply voltage and generate output signals for external circuits compatible with the first supply voltage;
• code that defines a second interface designed to handle input signals from external circuits compatible with a second supply voltage and generate output signals for external circuits compatible with the second supply voltage;
• and
• code that defines a selective coupling of the first interface or second interface to the core,
• such that the core and selected interface of the integrated circuit are coupled to one external positive supply.