A Fedex Federal Express Airbus A300-600, registration N751FD performing freight flight FX-240 from Memphis,TN (USA) to Calgary,AB (Canada) with 2 crew, was enroute at FL320 about 160nm south of Calgary when the crew received an avionics smoke warning, the crew did not detect any smoke or smell of smoke. The crew worked the related checklist, the smoke indication persisted however. The crew declared emergency, turned the aircraft and diverted to Great Falls,MT (USA) for a safe landing . . .