1+_____________________________________________________________________
 ] AUTHOR:            ]                             ] DR:              ]
 ] T. METCALF         ]    PASS PROGRAM NOTE        ]      37533       ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE: AUG. 1987  ]
 ] IBM/282-8436       ]      RELEASE NOTE( )        ] REV A: 02/12/93  ]
 ]____________________]_____________________________]__________________]
 ] OI/FLIGHT EFFECTIVITY:        ]  USER AFFECTED:                     ]
 ] REL 18 AND SUBS               ]  CREW ( )  GROUND (X)  DUMP ONLY ( )]
 ]_______________________________]_____________________________________]
 ]        MAJOR SOFTWARE AREA:       ] OPS MODES AFFECTED:             ]
 ]SSW (X)  GNC ( )  VU ( )  SM/PL ( )] 0, G1, G2, G3, G6, G8, G9, S2,  ]
 ]                                   ] S4, PL9                         ]
 ]_____________________________________________________________________]
 ] SOFTWARE SUB-AREA: COMMFAULTS, MDM                                  ]
 ]_____________________________________________________________________]
 ] PRINCIPAL FUNCTIONS: SANU, SBIO                                     ]
 ]_____________________________________________________________________]
 ] TITLE:                                                              ]
 ] SETTING OF NSP AND MTU COMMFAULTS AFTER AN FF MDM BYPASS            ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ]                                                                     ]
 ] WHEN A FLIGHT FORWARD (FF) MDM RETURN WORD ELEMENT IN THE HFE/HDA   ]
 ] INPUT TRANSACTION IS BYPASSED, BYPASS BITS ARE SET IMMEDIATELY FOR  ]
 ] ALL ELEMENTS IN THE FAILED MDM IN THE HIGH FREQUENCY EXECUTIVE      ]
 ] (HFE), MFE, NSP, AND MTU INPUT TRANSACTIONS. THE COMMFAULTS ARE, IN ]
 ] GENERAL, NOT SET UNTIL THE NEXT TIME THE TRANSACTION IN QUESTION    ]
 ] OCCURS. THIS PREVENTS "SLIVERING" PROBLEMS WHICH COULD OCCUR IF ONE ]
 ] TRANSACTION SETS OR RESETS ANOTHER TRANSACTION'S COMMFAULTS. THERE  ]
 ] ARE SOME EXCEPTIONS TO THIS RULE. MTU INPUT, NSP INPUT, SRB DATA    ]
 ] ACQUISITION, AND IMU INPUT (GNC OPS 9 ONLY) TRANSACTIONS COMMFAULTS ]
 ] ARE ALL IN THE SAME COMMFAULT WORD. AFTER AN FF1, 2 ,OR 3 MDM       ]
 ] RETURN WORD FAILURE, THE NEXT INITIATION OF ANY OF THOSE FOUR       ]
 ] TRANSACTIONS WILL CAUSE THE COMMFAULTS FOR NSP AND MTU INPUT TO BE  ]
 ] SET.                                                                ]
 ]                                                                     ]
 ] THESE EXCEPTIONS ARE NOT A PROBLEM BECAUSE OF THE FOLLOWING DESIGN  ]
 ] CONSIDERATIONS:                                                     ]
 ]                                                                     ]
 ] A. THE MTU READ OCCURS IN CYCLE 15 AND THE MTU COMMFAULTS ARE MOVED ]
 ]    IN THE ICC BUFFER ON CYCLE 16 BY THE PC2 INTERRUPT HANDLER. ALL  ]
 ]    OTHER ROUTINES WHICH USE THE MTU COMMFAULTS GET THEM FROM THE    ]
 ]    ICC BUFFER. THIS MEANS THAT THE MTU COMMFAULTS ARE ONLY READ OR  ]
 ]    SET IN FCOS ROUTINES WITH SYNC AND DISABLE PROTECTION, WHICH     ]
 ]    PRECLUDES SLIVERING PROBLEMS WITH THEM.                          ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ]CONCURRENCE:                           ]APPROVAL:                    ]
 ]IBM:   JEAN L. ZOPHY      DATE 04/13/93]                             ]
 ]    --------------------      ---------]                             ]
 ]FDSD:   W. R. PRUETT      DATE 04/15/93]                             ]
 ]     -------------------      ---------] DARRELL E. STAMPER 04/28/93 ]
 ]PF MGR: ERIC C. BINGHAM   DATE 04/13/93]------------------- -------- ]
 ]       -----------------      ---------] CHAIRMAN, SASCB      DATE   ]
 ]_______________________________________]_____________________________]
 @



1+_____________________________________________________________________
 ]                       SUPPLEMENTAL SHEET                            ]
 ]_____________________________________________________________________]
 ] AUTHOR:            ]                             ] DR:              ]
 ] T. METCALF         ]    PASS PROGRAM NOTE        ]       37533      ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE: AUG. 1987  ]
 ] IBM/282-8436       ]      RELEASE NOTE ( )       ] REV A: 02/12/93  ]
 ]____________________]_____________________________]__________________]
 ] TITLE:                                                              ]
 ] SETTING OF NSP AND MTU COMMFAULTS AFTER AN FF MDM BYPASS            ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ]                                                                     ]
 ] B. NSP READ OCCURS ON CYCLES 4N (I.E., 0,4,8,12,16,20). THE NSP     ]
 ]    COMMFAULT BITS ARE EXAMINED BY AIE_SSIP ICC COLLECTION LOGIC ON  ]
 ]    THE FOLLOWING CYCLES (1,5,9,13,17,21). IF NSP DATA IS PRESENT    ]
 ]    AND NOT COMMFAULTED, IT IS LOADED INTO THE ICC BUFFER. MTU INPUT ]
 ]    IS INITIATED AT THE SSIP TIMER INTERRUPT AT CYCLE 15 AND SRB DA  ]
 ]    AT THE SSIP TIMER INTERRUPT EACH CYCLE WHEN IT IS ACTIVE. IF THE ]
 ]    SSIP COLLECTION CYCLE RAN INTO THE NEXT CYCLE, IT COULD GET      ]
 ]    SLIVERED BY THE SETTING OF THE COMMFAULTS. HOWEVER, THE          ]
 ]    DIFFERENCE IN THE COLLECTION PROCESSING IS INSUFFICIENT TO CAUSE ]
 ]    LOSS OF SYNC AND THE SUBSEQUENT ROUTING CYCLE WOULD NOT ROUTE    ]
 ]    THE DATA BECAUSE OF THE LOGIC IN AIE_SSIP TO DETECT SUCH         ]
 ]    OVERRUNS (GPC ERROR 020D) OF THE SSIP COLLECTION CYCLE.          ]
 ]                                                                     ]
 ] C. IMU INPUT IS INITIATED AT AN OFFSET OF 14 OR 20 MSEC FROM THE    ]
 ]    SSIP TIMER IN OPS GNC9. IF THE IMU INPUT OCCURS ON THE CYCLE     ]
 ]    FOLLOWING THE MDM RETURN WORD BYPASS AND IN AN ICC COLLECTION    ]
 ]    CYCLE (4N + 1), THEN I/O ERRORS WOULD HAVE BEEN INCURRED ON THE  ]
 ]    MDM IN THE HDA INPUT FOR THE PRECEDING 2 CYCLES (4N-1 AND 4N).   ]
 ]    ASSUMING THAT THE MDM RETURN WORD FAILURE IMPLIES AN MDM FAILURE,]
 ]    THE NSP INPUT WOULD ALSO HAVE INCURRED AN I/O ERROR ON CYCLE 4N, ]
 ]    AND THE NSP COMMFAULT WOULD ALREADY BE SET. THESE EVENTS, IN     ]
 ]    ORDER, WOULD BE AS FOLLOWS:                                      ]
 ]                                                                     ]
 ]   CYCLE 4N-1 + .026          -HDA INPUT ERROR #1                    ]
 ]   CYCLE 4N   + 0             -NSP INPUT -I/O ERROR - SET COMMFAULT  ]
 ]   CYCLE 4N   + .026          -HDA INPUT ERROR #2: BYPASS MDM RETURN ]
 ]                               WORD + ELEMENTS                       ]
 ]   CYCLE 4N+1 + 0             -START SSIP COLLECTION CYCLE           ]
 ]   CYCLE 4N+1 + .014 OR .020  -INITIATE IMU INPUT - OR BYPASS BITS   ]
 ]                               INTO COMMFAULTS (NO CHANGE IN NSP     ]
 ]                               COMMFAULT).                           ]
 ]                                                                     ]
 ] D. IMU INPUT CAN ALSO BE INITIATED BY SVC IN GME. THIS IS NOT A     ]
 ]    PROBLEM SINCE GME RUNS AT LOWER PRIORITY THAN SSIP AND CANNOT    ]
 ]    INTERRUPT IT.                                                    ]
 ]_____________________________________________________________________]
 ]USER RESPONSE:                                                       ]
 ]                                                                     ]
 ]NONE.                                                                ]
 ]                                                                     ]
 ]                                                                     ]
 ]_____________________________________________________________________]
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