A320 DISCOVERS FMGC HAS LOCKED ON A SINGLE PAGE SHORTLY AFTER TKOF. CONDUCT OPERATION TO DESTINATION WITH ATC ASSISTANCE AND RAW DATA. DECLARE A PRECAUTIONARY EMERGENCY FOR THEIR ARRIVAL AT SCHEDULED DESTINATION.

Narrative

ALL OPS NORMAL UNTIL ZZZ CTR CLRED US PRESENT POS TO VOR ENRTE TO ZZZ1. DISCOVERED WE HAD ZERO CTL OR INPUT TO THE FMGC. ADVISED ATC OF THE ISSUE. THEY GAVE US A HDG; REACHING ZZZ1 APCH; WE DECLARED AN EMER AND LANDED WITHOUT EVENT. WHILE STILL ON CLB; WE DISCOVERED WE COULD NOT ADDRESS THE FMGC. THE ONLY PAGE DISPLAYED AND AVAILABLE WAS THE FLT PLAN PAGE. ACARS ACCESS WAS NORMAL. ADVISED ATC OF THE NAV ISSUE AND THEY WERE WILLING TO GIVE US HDGS UNTIL WE SORTED OUT OUR ISSUES. FMGC PAGE NEVER ADVANCED FROM OUR INITIAL TKOF DISPLAY. CONFIRMED THAT ALL SYS WERE NORMAL AND THAT RVSM OPS WERE ALLOWED. TRADED ACARS MESSAGES WITH MAINT CTL AND ZZZZZ. MAINT CTL HAD NEVER EXPERIENCED THIS TYPE OF FAILURE. TRIED CIRCUIT BREAKER CYCLING FOR EACH MCDU WITH NO IMPROVEMENT. MAINT CTL SUGGESTED WE COULD USE EMER AUTH TO CYCLE THE FMGC'S WHICH CREW WAS UNWILLING TO ATTEMPT. CHKED COURSE AND NAVAIDS USING STANDBY NAV FUNCTIONS OF THE RMP AND APPEARED DISPLAYS ON NAV DISPLAY WERE ACCURATE AND RAW DATA WAS AVAILABLE. DISPATCH AGREED THE WX IN ZZZ1 WAS GOOD AND CREW WAS OK WITH CONTINUING OP TO ZZZ1. THE GENERAL WX WAS GOOD UNTIL ZZZ1 ARR WHICH SHOULD BE AN INITIAL ILS BUT VFR PRIOR TO OM. ACFT APPEARED TO UPDATE THE GROSS WT OF OUR FLT. USED FLT MANUAL TO DETERMINE LNDG REF SPDS. USED ACARS LNDG PERFORMANCE DATA FEATURE. DID NOT KNOW/SELECT AN APCH DURING INITIAL FMGC LOADING FOR ZZZ1. PLANE WAS SHOWING 800 FT FOR A LNDG ELEVATION; SO WE FELT REASONABLY SURE THE PLANE WAS HAPPY WITH THE DEST. SINCE WE COULD NOT SELECT AN APCH OR ACTIVATE AND CONFIRM; WE DID NOT KNOW HOW THE EGWS WOULD REACT. ZZZ ALTIMETER WAS HIGHER THAN ZZZ1 ALTIMETER WHICH COULD RESULT IN A 500 FT CABIN PRESSURE ERROR. DECLARED EMER WITH ZZZ1 APCH TO GET ANY RELIEF AND LATITUDE WE MAY NEED IF WE HAD NAV ISSUES ON THE APCH. LANDED WITHOUT EVENT. LCL CONTRACT MAINT RESET SYS AND COULD NOT DUPLICATE THE FAULT. NEXT LEG WAS NORMAL.