Flash-based FPGA with secure reprogramming

1. An integrated circuit including:

programmable circuitry;

a flash data input I/O pad;

a flash memory array coupled to the programmable circuitry for configuring the programmable circuitry;

flash programming circuitry for programming the flash memory array;

on-chip intelligence coupled to the programming circuitry and to the flash data input pad, the on-chip intelligence including a decryption engine coupled to the flash data input I/O pad and storing a decryption key, the on-chip intelligence configured to refresh the data stored in the flash memory using data from one of data stored in the flash memory array and data entered onto the integrated circuit from the flash data input I/O pad and decrypted by the decryption engine.

2. The integrated circuit of claim 1 wherein the on-chip intelligence comprises a microcontroller.

3. The integrated circuit of claim 1 wherein the on-chip intelligence comprises a state machine.

4. The integrated circuit of claim 1 wherein the on-chip intelligence is further configured to take the integrated circuit out of a normal operating mode prior to refreshing the data stored in the flash memory array.

5. The integrated circuit of claim 1 wherein the on-chip intelligence includes:

means for taking the integrated circuit out of normal operating mode;

means for performing a current row operation including:

means for reading the current row configuration data from the memory into local row latches;

means for erasing flash memory cells in the row;

means for programming the memory cells in the current row from the latched row configuration data;

means for determining whether the current row is not the last row in the memory, and for performing the current row operation on the next row to be refreshed if the current row is not the last row in the memory; and

means for returning the integrated circuit to normal operation if the current row was the last row to be refreshed.

6. The method of claim 5 , further comprising:

means for setting a row counter to zero;

means for determining whether the current row is the last row in the memory after programming the memory cells in the current row;

means for incrementing the row count and repeating performance of the current row operation if the current row is not the last row in the memory.

7. The method of claim 6 , further comprising means for programming any previously unprogrammed memory cells in the current row before erasing all the flash memory cells in the row.

8. The integrated circuit of claim 1 wherein the on-chip intelligence includes:

means for taking the integrated circuit out of normal operating mode;

means for performing a current row operation including:

means for erasing flash memory cells in the row;

means for loading and decrypting encrypted row configuration data for the current row;

means for programming the memory cells in the current row from the loaded and decrypted row configuration data;

means for performing the current row operation on the next row to be reprogrammed if the current row is not the last row to be reprogrammed; and

means for returning the integrated circuit to normal operation if the current row was the last row to be reprogrammed.

9. The method of claim 8 , further comprising:

means for setting a row counter to zero;

means for determining whether the current row is the last row in the memory after programming the memory cells in the current row; and

means for incrementing the row count and repeating performance of the current row operation if the current row is not the last row in the memory.

10. The method of claim 9 , further comprising means for programming any previously unprogrammed memory cells in the current row before erasing all the flash memory cells in the row.