 +_____________________________________________________________________
 ] AUTHOR:            ]                             ] SMS: B08127A     ]
 ]  P. WILSON         ]    BFS PROGRAM NOTE         ] DR:              ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE : 10/12/81  ]
 ] RI/KSC  861-4656   ]      RELEASE NOTE ( )       ] REV B:  5/30/96  ]
 ]____________________]_____________________________]__________________]
 ] OI/FLIGHT EFFECTIVITY:        ]  USER AFFECTED:                     ]
 ]       OI8B AND SUBS           ]  CREW (X)  GROUND (X)  DUMP ONLY ( )]
 ]_______________________________]_____________________________________]
 ]           MAJOR SOFTWARE AREA:            ] OPS MODES AFFECTED:     ]
 ]BSL( ) BSS(X) GNC( ) SEQ( ) SM/SP( ) IPL( )]    1, 3, AND 6          ]
 ]_____________________________________________________________________]
 ] SOFTWARE SUB-AREA:  MTU RM                                          ]
 ]_____________________________________________________________________]
 ] PRINCIPAL FUNCTIONS:  MGO38101/3.8.2.1                              ]
 ]_____________________________________________________________________]
 ] TITLE:                                                              ]
 ]          BFS MTU ACCUMULATOR SWITCH / SELECTION                     ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ] 1.) WHEN BFS STARTS TO TRACK PASS, IT IS ACCEPTABLE FOR BFS TO      ]
 ] SELECT AN ACCUMULATOR SOURCE DIFFERENT FROM THAT WHICH PASS HAS     ]
 ] SELECTED BECAUSE OF THE BFS MID-VALUE SELECTION LOGIC.              ]
 ]                                                                     ]
 ] 2.) BFS MAY OCCASIONALLY CHANGE THE MTU ACCUMULATOR USED TO UPDATE  ]
 ] GMT WITHOUT THE OCCURRENCE OF AN I/O ERROR OR ANY INDICATION OF A   ]
 ] PASS MTU PROBLEM. THIS CHANGE IN ACCUMULATORS DOES NOT AFFECT THE   ]
 ] MANNER IN WHICH BFS TRACKS PASS NOR DOES IT INTRODUCE ANY ERRORS    ]
 ] INTO THE BFS MAINTAINED GMT OR MET.                                 ]
 ]                                                                     ]
 ] 3.) IF BFS IS LEFT IN THE STANDALONE STATE FOR AN EXTENDED PERIOD   ]
 ] OF TIME, AN 'I/O RESET EXEC' COMMAND WILL NOT BE SUFFICIENT TO      ]
 ] CAUSE BFS TO RESELECT AN MTU ACCUMULATOR. ANALYSIS HAS SHOWN THAT   ]
 ] THE INTERNAL GMT OF A STANDALONE BFS MAY DRIFT IN EXCESS OF THE     ]
 ] 800 MICROSECOND MTU TOLERANCE IN AS LITTLE AS 64 SECONDS.           ]
 ]_____________________________________________________________________]
 ] USER RESPONSE:                                                      ]
 ] FOR 1.) AND 2.) ABOVE, NO RESPONSE IS REQUIRED. SELECTION OF AN MTU ]
 ] ACCUMULATOR DIFFERENT FROM PASS OR AN INFREQUENT ACCUMULATOR SWITCH ]
 ] HAS NO DISCERNIBLE EFFECTS ON BFS PERFORMANCE NOR HAS ANY EFFECTS   ]
 ] ON THE ABILITY OF BFS TO ASSUME CONTROL OF THE VEHICLE.             ]
 ]                                                                     ]
 ] FOR 3.) ABOVE, BFS GMT MUST BE RE-INITIALIZED IN ORDER FOR AN MTU   ]
 ] ACCUMULATOR TO BE SELECTED. THIS CAN ONLY BE ACCOMPLISHED BY        ]
 ] MANUALLY TRANSITIONING BFS TO OPS 101 OR 301 FROM OPS 000, OR TO    ]
 ] OPS 301 FROM OPS 106. IF THESE TRANSITIONS ARE PROCEDURALLY         ]
 ] UNACCEPTABLE, BFS MUST REMAIN ON INTERNAL TIME.                     ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ]CONCURRENCE:                           ]APPROVAL:                    ]
 ]RI: <S> D. CORBIN         DATE 05/30/96]                             ]
 ]    --------------------      ---------]                             ]
 ]ASD:  ERIC C. BINGHAM     DATE 06/11/96]                             ]
 ]    --------------------      ---------] DARRELL E. STAMPER 06/17/96 ]
 ]PF MGR:   MARCIA KERR     DATE 06/14/96]------------------- -------- ]
 ]       -----------------      ---------] CHAIRMAN, SASCB      DATE   ]
 ]_____________________________________________________________________]
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