What was found
AIRCRAFT WAS NOT GROUNDED: ON IMC APPROACH ILS 18R, CLEARANCE CANCELED TO NOW FLY RVAV-Z 13R APPROACH. DURING FMS LOADING PRECISELY WHEN RNP .3 WAS ENTERED BOTH FMS 1 & 2 FROZE, BACKUP NAV APPNUCIATED, ALL PERFORMED CALCULATIONS LOST, NO INIT LOAD AND NO SEC FLIGHT PLAN AVAILABLE BECAUSE BOTH FMS 1 & 2 REMAINED FROZEN, DECLARED EMERGENCY, LANDED 13R DFW UNEVENTFUL. MAINTENANCE REPLACED FLIGHT MANAGEMENT AND GUIDANCE COMPUTER #2 (FMGC) PER AMM 22-83-34.