Method and apparatus for securing configuration scan chains of a programmable device

Scan chain circuitry on an integrated circuit device, said scan chain circuitry comprising:

• a plurality of memory elements on said integrated circuit device;
• a plurality of control elements on said integrated circuit device, each of said control elements being located between respective ones of said plurality of memory elements for controllably connecting said plurality of memory elements into a scan chain;
• and
• a plurality of scan enable activation elements on said integrated circuit device, each of said scan enable activation elements controlling a respective subplurality of said plurality of control elements for connecting a respective subplurality of said plurality of memory elements into said scan chain;
• wherein:
• each of said scan enable activation elements is actuated, to connect its respective subplurality of said plurality of memory elements into said scan chain, by a first enable signal common to more than one of said scan enable activation elements, and a second enable signal for said one of said scan enable activation elements.

A method of entering configuration data into a programmable integrated circuit device, said method comprising:

• deriving a respective security signal from each respective group of a plurality of groups of configuration memory elements of said programmable integrated circuit device;
• applying an enable signal and respective ones of said security signal to respective scan enable activation elements of said programmable integrated circuit device to connect said configuration memory elements in all of said respective groups into a scan chain;
• and
• clocking said configuration data through said scan chain.