1+_____________________________________________________________________
  AUTHOR:                                          DR:              
  P. TICE                PASS PROGRAM NOTE              107001      
 ____________________                             __________________
  ORG/PHONE:          OPS NOTE (X)  USER NOTE ( )  DATE:  03/13/92  
  LORAL/282-7297           RELEASE NOTE( )         REV C: 02/11/94  
 ___________________________________________________________________
  OI/FLIGHT EFFECTIVITY:          USER AFFECTED:                     
      OI-22                       CREW (X)  GROUND (X)  DUMP ONLY ( )
 ____________________________________________________________________
         MAJOR SOFTWARE AREA:        OPS MODES AFFECTED:             
 SSW (X)  GNC ( )  VU ( )  SM/PL ( )     ALL                         
 _____________________________________________________________________
  SOFTWARE SUB-AREA:  MMU, TRANSITIONS                                
 _____________________________________________________________________
  PRINCIPAL FUNCTIONS:   SDPS                                         
 _____________________________________________________________________
  TITLE:                                                              
     EFFECTS OF STALE COMMANDER/LISTENER FLAG DURING MMU OVERLAYS     
 _____________________________________________________________________
  DESCRIPTION:                                                        
  1) IF AN OPS TRANSITION IS REQUESTED THAT INVOLVES A SET EXPANSION  
  WHICH INCLUDES GPCS THAT COMMANDED THEIR PREVIOUS MASS MEMORY       
  OPERATION, MASS MEMORY I/O ERRORS MAY BE EXPECTED WITH THE POSSIBLE 
  FAIL-TO-SYNC OF ONE OR TWO GPCS. (NOTE: THE GPC COMMANDING THE MMU  
  OVERLAY IS SUBJECT TO THE LOGIC IN 4 BELOW.)                        
                                                                      
  2) IF A GPC FREEZE-DRY REQUEST IS MADE TO A GPC THAT HAS NOT        
  COMMANDED ITS PREVIOUS MASS MEMORY OPERATION, A SINGLE MASS MEMORY  
  I/O ERROR MAY BE EXPECTED.                                          
                                                                      
  3) IF THE GPC COMMANDING THE MASS MEMORY OVERLAY (PER THE LOGIC     
  DESCRIBED IN 4 BELOW) IS DROPPED DURING THE OPS TRANSITION, A SINGLE
  MASS MEMORY I/O ERROR MAY BE EXPECTED FROM THE REMAINING LISTENER   
  GPCS.                                                               
                                                                      
  FOR ALL THE ABOVE CASES, A RETRY OF THE OVERLAY ON THE SAME MMU     
  BUS OR ON THE ALTERNATE MMU WILL BE SUCCESSFUL.                     
                                                                      
  4) SINCE THE SECONDARY MMU (USUALLY MMU2) PREPOSITION IS THE LAST   
  ONE ISSUED DURING AN MMU OVERLAY, THE GPC COMMANDING THE SECONDARY  
  MMU WILL COMMAND THE OVERLAY USING THE PRIMARY MMU.  THE EXCEPTIONS 
  ARE MMU OPS TRANSITIONS FROM OPS0 TO ANY OPS AND THE G1 OVERLAY     
  FROM G9 VIA G3.                                                     
                                                                      
  5) THIS FLAG IS ALSO USED IN SUCH A MANNER THAT THE GPC WHICH       
  COMMANDS THE MMU OVERLAY IS SPECIFIED BY THE CURRENT OPS NBAT       
  VERSES THE NEW OPS NBAT.                                            
 _____________________________________________________________________
 CONCURRENCE:                           APPROVAL:                    
 LORAL:  JEAN L. ZOPHY     DATE 03/15/94                             
       ------------------      ---------                             
 FDSD:  ROBERT N. HINSON   DATE 03/15/94                             
      -------------------      --------- DARRELL E. STAMPER 03/17/94 
 PF MGR:  ERIC C. BINGHAM  DATE 03/15/94------------------- -------- 
        ------------------     --------- CHAIRMAN, SASCB      DATE   
 ____________________________________________________________________
 @





1+_____________________________________________________________________
                                                                      
                        SUPPLEMENTAL SHEET                            
                                                                      
 _____________________________________________________________________
  AUTHOR:                                          DR:              
  P. TICE                PASS PROGRAM NOTE              107001      
 ____________________                             __________________
  ORG/PHONE:          OPS NOTE (X)  USER NOTE ( )  DATE:  03/13/92  
  LORAL/282-7297           RELEASE NOTE( )         REV C: 02/11/94  
 ___________________________________________________________________
  TITLE:                                                              
     EFFECTS OF STALE COMMANDER/LISTENER FLAG DURING MMU OVERLAYS     
                                                                      
 _____________________________________________________________________
 USER RESPONSE:                                                       
                                                                      
  1) BE AWARE THAT MASS MEMORY I/O ERRORS AND POSSIBLY ONE OR TWO     
  GPCS FAILING-TO-SYNC MAY OCCUR ON OPS TRANSITIONS THAT EXPAND A     
  REDUNDANT SET TO INCLUDE FORMER MMU COMMANDER GPCS.  THE WINDOW     
  OF EXPOSURE FOR TWO OUT OF FOUR GPCS TO FTS IS LIMITED TO THE FIRST 
  200 MILLISECONDS OF THE OVERLAY READ.  DUE TO THE UNPREDICTABLE     
  RESULTS WITH MULTIPLE BUS COMMANDERS, THE I/O ERROR LOG ENTRY       
  SIGNATURES CAN BE THE FOLLOWING: SIGNATURE MISMATCH, PARITY, S BIT, 
  E BIT, V BIT, SYNC ERROR, INITIAL TIMEOUT AND TIMEOUT.  ANY GPC(S)  
  THAT FTS WILL REQUIRE AN IPL BEFORE AN ATTEMPT IS MADE TO JOIN IT   
  TO THE REDUNDANT SET.  WHETHER OR NOT A FTS OCCURS, THE OPS         
  TRANSITION/EXPANSION WILL BE SUCCESSFUL ON THE OVERLAY RETRY USING  
  THE SAME MASS MEMORY BUS OR UPON SWITCHOVER TO THE ALTERNATE MMU.   
  (SEE 4 BELOW)                                                       
                                                                      
  2) BE AWARE THAT A SINGLE MM I/O ERROR WILL OCCUR ON GPC FREEZE-DRY 
  ATTEMPTS IF THAT GPC DIDN'T COMMAND ITS PREVIOUS MASS MEMORY        
  OPERATION.  THE SPEC 0 "STORE   MC=XX" FIELD WILL INDICATE THAT THE 
  FD ATTEMPT WAS SUCCESSFUL WHEN XX EQUALS THE SELECTED MC IN ITEM 45.
  THE SIGNATURE IN THE I/O ERROR LOG ENTRY WILL BE INITIAL TIMEOUT.   
                                                                      
  3) BE AWARE THAT A SINGLE MM I/O ERROR WILL OCCUR ON OPS TRANSITIONS
  THAT DROP THE COMMANDING GPC (PER 4 BELOW) AND WILL BE ANNUNCIATED  
  BY THE REMAINING LISTENER GPCS.  THE SIGNATURE IN THE I/O ERROR LOG 
  ENTRY WILL BE INITIAL TIMEOUT.                                      
                                                                      
  4) BE AWARE THAT THE GPC COMMANDING THE SECONDARY MMU WILL COMMAND  
  MMU OVERLAYS USING THE PRIMARY MMU, EXCEPT FOR OPS 0 OVERLAYS AND   
  THE G1 OVERLAY (FROM G9 VIA G3).                                    
                                                                      
  5) BE AWARE THAT THE MMU OVERLAY COMMANDER WILL BE TAKEN FROM THE   
  CURRENT OPS NBAT VERSES THE NEW OPS NBAT.                           
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
 _____________________________________________________________________
 @
