I/O cell configuration for multiple I/O standards
AssigneeAltera Corporation
InventorsCameron McClintock, Richard G. Cliff, Bonnie I. Wang
Life of this patent
Estimating the term…
Abstract
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.
Claims15
A programmable logic integrated circuit comprising:
- a plurality of first I/O circuits coupled to a supply voltage and a first configurable reference voltage;
- and
- a plurality of second I/O circuits coupled to the supply voltage and a second configurable reference voltage, wherein the first configurable reference voltage is different from the second configurable reference voltage and the plurality of first I/O circuits is compatible with a first I/O standard based on the first configurable reference voltage and the plurality of second I/O circuits compatible with a second I/O voltage standard based on the second configurable reference voltage.
A method of operating a programmable logic integrated circuit comprising:
- programmably selecting a first reference voltage level to be coupled to a first I/O circuit to select a first I/O standard the first I/O circuit will be compatible with;
- programmably selecting a second reference voltage level to be coupled to a second I/O circuit to select a second I/O standard the second I/O circuit will be compatible with;
- and
- coupling the first I/O circuit and the second I/O circuit to a supply voltage.
Dependencies are inferred from the claim text.