 +_____________________________________________________________________
 ] AUTHOR:            ]                             ] DR:              ]
 ] M. MILLER          ]    PASS PROGRAM NOTE        ]     47311  *     ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE: AUG. 1987  ]
 ] LSIS/282-7167      ]      RELEASE NOTE( )        ] REV B: 03/18/96  ]
 ]____________________]_____________________________]__________________]
 ] OI/FLIGHT EFFECTIVITY:        ]  USER AFFECTED:                     ]
 ] OI-02 AND SUBS                ]  CREW ( )  GROUND (X)  DUMP ONLY ( )]
 ]_______________________________]_____________________________________]
 ]        MAJOR SOFTWARE AREA:       ] OPS MODES AFFECTED:             ]
 ]SSW (X)  GNC ( )  VU (X)  SM/PL ( )] G9                              ]
 ]_____________________________________________________________________]
 ] SOFTWARE SUB-AREA:  CYCLE-WRAP, DED-DISP, TCS, GPC, ECP             ]
 ]_____________________________________________________________________]
 ] PRINCIPAL FUNCTIONS: V4.13, V5.1.4, SDPS                            ]
 ]_____________________________________________________________________]
 ] TITLE:                                                              ]
 ]        I/O AND PROCESS CYCLE WRAPS IN G9                            ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:  * DRS 100716 & 104125                                 ]
 ]                                                                     ]
 ] DURING HEAVY I/O ACTIVITY IN G9 (E.G. DDU TESTS, RJD TOGGLE, TCS    ]
 ] SEQUENCES, IMU OPERATIONS AND THE SENSOR SELF TESTS)                ]
 ] I/O CYCLE WRAPS MAY OCCUR DUE TO A DISPATCH OF HIGH PRIORITY I/O    ]
 ] CAUSING A DELAY IN I/O COMPLETION PROCESSING FOR A LOWER PRIORITY   ]
 ] I/O.  LOWER PRIORITY I/O COMPLETION IS HELD OUT UNTIL THE HIGH      ]
 ] PRIORITY I/O COMPLETE INTERRUPT HAS BEEN PROCESSED.  THE MOST       ]
 ] COMMON I/O CYCLE WRAPS IN G9 ARE PMU OI/PL RAM (GP7 CODE OD),       ]
 ] SRB (GP7 CODE 6), AND D/L (GP7 CODE 5).                             ]
 ]                                                                     ]
 ] PROCESSES WHICH WAIT FOR I/O COMPLETION (E.G. DGI, HDA, ETC. IN G9) ]
 ] MAY INCUR A PROCESS CYCLE WRAP (GP2 CODE OD) AS A RESULT OF A DELAY ]
 ] IN I/O COMPLETION PROCESSING.                                       ]
 ]                                                                     ]
 ] BUS CONTENTION CAUSED BY SEVERAL FUNCTIONS OR PROCESSES REQUESTING  ]
 ] I/O ON THE SAME BUSES AND/OR I/O ERROR PROCESSING WILL FURTHER      ]
 ] AGGRAVATE THE PROBLEM.                                              ]
 ]_____________________________________________________________________]
 ] USER RESPONSE:                                                      ]
 ] CERTAIN FUNCTIONS (SUCH AS IMU, ECPS, RJD, AND TCS SEQUENCES)       ]
 ] SHOULD BE CONSIDERED MUTUALLY EXCLUSIVE TO PRECLUDE I/O IMPACT      ]
 ] TO EACH OTHER.                                                      ]
 ] SINCE CERTAIN ECPS ARE DEPENDENT ON THE PMU OI/PL RAM READS FOR     ]
 ] MAIN ENGINE POSITION FEEDBACK DATA, THE USER SHOULD PROCEDURALLY    ]
 ] AVOID CONTENTION WITH OTHER FUNCTIONS WHICH INITIATE HIGHER         ]
 ] PRIORITY I/O, E.G. IMU, DDU, ETC.                                   ]
 ]_____________________________________________________________________]
 ]CONCURRENCE:                           ]APPROVAL:                    ]
 ]LSIS:   JEAN L. ZOPHY     DATE 04/23/96]                             ]
 ]     -------------------      ---------]                             ]
 ]ASD:   ERIC C. BINGHAM    DATE 04/23/96]                             ]
 ]     -------------------      ---------] DARRELL E. STAMPER 04/29/96 ]
 ]PF MGR: ERIC C. BINGHAM   DATE 04/23/96]------------------- -------- ]
 ]       -----------------      ---------] CHAIRMAN, SASCB      DATE   ]
 ]_______________________________________]_____________________________]
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