AN EMBRAER 145 FLC DSNDED BELOW ASSIGNED ALT NEAR OXI.

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APCHING ORD ON KNOX ARR AT FL230 WAS GIVEN HOLDING AT HALIE INTXN; 11000 FT; L TURNS AND HURRY DOWN. FO (PNF) STARTS PROGRAMMING HOLD INTO FMS. AT LEAST TWICE MORE WAS TOLD TO 'HURRY DOWN.' HOLD IN FMS UNIT DISPLAYS WRONG VOR AND RADIALS WHICH BRINGS MY HEAD DOWN DOUBLECHKING ARR IN APCH PLATES. WE SET UP VOR TO ESTABLISH POS AND DSNDING '12000 FT FOR 11000 FT.' ATC QUERIED AS TO IF WE WERE AT 12000 FT. PUZZLED; WE LEVELED AT 12000 FT AND ASKED IF ORIGINAL CLRNC WAS 11000 FT. CTLR SAID NO; STAY AT 12000 FT. THERE WAS AN ACFT AT 11000 FT HOLDING AT SAME INTXN WE SAW VISUALLY (NOT KNOWING HE WAS AT 11000 FT BUT THERE WAS NEVER A CONFLICT). PROB AROSE: FO WROTE DOWN 11000 FT IN ORIGINAL INSTRUCTIONS AND READ BACK 11000 FT. WE PUT 11000 FT IN ALT SELECT. POINT AND REPEAT 11000 FT. EITHER WE BOTH MISINTERPED ORIGINAL CLRNC; WERE GIVEN 12000 FT IN ONE OF THE HURRY DOWN CLRNCS; OR 11000 FT IS WHAT WAS GIVEN. CONTRIBUTION: PROGRAMMING FMS KEPT GIVING US WRONG DATA. HOLD WOULD NOT ARM CORRECTLY; CAUSING COCKPIT DISTR AND LEADING TO OUR WORKLOAD INCREASE. I ONLY HAVE APPROX 130 HRS IN TYPE. FUTURE CORRECTIONS: I WILL USE VOR BACKUP IMMEDIATELY WHILE OTHER PLT PROGRAMS FMS. THIS WILL GIVE US A QUICKER REDUNDANCY AND NOT AS MUCH 'HURRY' AS WE APCH THE FIX.