PG As ▁are ▁generally ▁preferred . ▁Sometimes ▁both ▁C PL D s ▁and ▁F PG As ▁are ▁used ▁in ▁a ▁single ▁system ▁design . ▁In ▁those ▁designs , ▁C PL D s ▁generally ▁perform ▁gl ue ▁logic ▁functions , ▁and ▁are ▁responsible ▁for ▁“ boot ing ” ▁the ▁F P GA ▁as ▁well ▁as ▁cont rolling ▁reset ▁and ▁boot ▁sequence ▁of ▁the ▁complete ▁circuit ▁board . ▁Therefore , ▁depending ▁on ▁the ▁application ▁it ▁may ▁be ▁jud icious ▁to ▁use ▁both ▁F PG As ▁and ▁C PL D s ▁in ▁a ▁single ▁design . ▁ ▁Security ▁consider ations ▁ ▁F PG As ▁have ▁both ▁advantages ▁and ▁dis adv antages ▁as ▁compared ▁to ▁AS IC s ▁or ▁secure ▁micro process ors , ▁concerning ▁hardware ▁security . ▁F PG As ' ▁flex ibility ▁makes ▁mal icious ▁modifications ▁during ▁fabric ation ▁a ▁lower ▁risk . ▁Pre viously , ▁for ▁many ▁F PG As , ▁the ▁design ▁bit stream ▁was ▁exposed ▁while ▁the ▁F P GA ▁loads ▁it ▁from ▁external ▁memory ▁( typ ically ▁on ▁every ▁power - on ). ▁All ▁major ▁F P GA ▁vend ors ▁now ▁offer ▁a ▁spectrum ▁of ▁security ▁solutions ▁to ▁design ers ▁such ▁as ▁bit stream ▁encryption ▁and ▁authentication . ▁For ▁example , ▁Al tera ▁and ▁X il inx ▁offer ▁A ES ▁encryption ▁( up ▁to ▁ 2 5 6 - bit ) ▁for ▁bit stream s ▁stored ▁in ▁an ▁external ▁flash ▁memory . ▁ ▁F PG As ▁that ▁store ▁their ▁configuration ▁internally ▁in ▁non vol atile ▁flash ▁memory , ▁such ▁as ▁Mic