It's not a backdoor, just uncontrolled engineering. I bet you that the product manager never knew about this; it's provably a capability buried deep inside the ip block (which, logically, is used in other Actel parts).

Low cost ICs are incredibly complex nowadays, to the point defending even the most integrated, self-contained of parts is near impossible. I've been doing security analysis for manufacturers of high end microcontrollers and these parts are packed with features to the point they are just hard to seal. It's common to have a debugging/manufacturing/update/boot mechanism that can be used for attacks even when things are supposedly locked down.

All major CPU manufacturers publish detailed bug information, some of which can be used in exploits.

Here is one example:

http://download.intel.com/design/processor/specupdt/313279.p...