 +_____________________________________________________________________
  AUTHOR:                                          DR:              
   ANITA SENVIEL         PASS PROGRAM NOTE               107241*    
 ____________________                             __________________
  ORG/PHONE:          OPS NOTE (X)  USER NOTE ( )  DATE:  06/10/96  
   SSOAS/282-7086          RELEASE NOTE( )         REV A: 07/18/96  
 ___________________________________________________________________
  OI/FLIGHT EFFECTIVITY:          USER AFFECTED:                     
   OI-25                          CREW ( )  GROUND (X)  DUMP ONLY ( )
 ____________________________________________________________________
         MAJOR SOFTWARE AREA:        OPS MODES AFFECTED:             
 SSW ( )  GNC ( )  VU (X)  SM/PL ( )  G9                             
 _____________________________________________________________________
  SOFTWARE SUB-AREA:  DOWNLIST, TCS, LDB                              
 _____________________________________________________________________
  PRINCIPAL FUNCTIONS:  L5.3                                          
 _____________________________________________________________________
  TITLE:                                                              
          INCORRECT DOWNLIST OF MEC PREFLIGHT BITE READ DATA          
 _____________________________________________________________________
  DESCRIPTION:  *REFERENCE DR110229                                   
                                                                      
  NOTE:  IN THIS DESCRIPTION, SCENARIOS 1 AND 2 REFER TO DR107241.    
  SCENARIO 3 REFERS TO DR110229.                                      
                                                                      
  THERE ARE THREE POSSIBLE SCENARIOS WHERE THE MEC PREFLIGHT BITE DATA
  MAY BE PLACED IN THE WRONG MEC DOWNLIST BUFFER WHEN PERFORMING THE  
  READ-BITE-AFTER OPTION OF THE TCS MEC COMMAND OPERATOR (OPERATOR    
  CODE 19) OR THE READ PREFLIGHT BITE COMMAND OF THE TCS MEC READ     
  OPERATOR (OPERATOR CODE 20).  THE SCENARIOS ARE AS FOLLOWS:         
  1) A. THE USER EXECUTES A TCS SINGLE COMMAND WHILE ONE OR MORE TCS  
        SEQUENCES ARE EXECUTING, OR TWO OR MORE TCS SEQUENCES ARE     
        EXECUTING SIMULTANEOUSLY;                                     
     B. TWO OPERATORS ARE PROCESSED AT THE SAME TIME, THE FIRST OF    
        WHICH IS A TCS MEC READ OF THE PREFLIGHT BITE (THE USER       
        CANNOT CONTROL WHICH COMMAND IS PROCESSED FIRST WHEN MULTIPLE 
        COMMANDS ARE BEING EXECUTED SIMULTANEOUSLY);                  
                                                                      
 _____________________________________________________________________
  USER RESPONSE:                                                      
                                                                      
  FOR THE FIRST TWO SCENARIOS THE USER HAS THE FOLLOWING OPTIONS:     
   1) RELY SOLELY ON THE LDB DATA (ALTHOUGH THE D/L DATA WILL USUALLY 
      BE CORRECT, IT'S POSSIBLE THAT IT WILL APPEAR CORRECT DUE TO    
      STALE DATA WHEN IT'S REALLY INCORRECT).                         
                                                                      
                  - CONTINUED ON SUPPLEMENT PAGE -                    
                                                                      
 _____________________________________________________________________
 CONCURRENCE:                           APPROVAL:                    
 SSOAS:  JEAN L. ZOPHY     DATE 08/20/96                             
       ------------------      ---------                             
 ASD:  ERIC C. BINGHAM     DATE 08/20/96                             
     --------------------      --------- DARRELL E. STAMPER 08/22/96 
 PF MGR: ERIC C. BINGHAM   DATE 08/20/96------------------- -------- 
        -----------------      --------- CHAIRMAN, SASCB      DATE   
 ____________________________________________________________________
 @




 +_____________________________________________________________________
                                                                      
                        SUPPLEMENTAL SHEET                            
                                                                      
 _____________________________________________________________________
  AUTHOR:                                          DR:              
   ANITA SENVIEL         PASS PROGRAM NOTE               107241*    
 ____________________                             __________________
  ORG/PHONE:          OPS NOTE (X)  USER NOTE ( )  DATE:  06/10/96  
   SSOAS/282-7086          RELEASE NOTE( )         REV A: 07/18/96  
 ___________________________________________________________________
  TITLE:                                                              
          INCORRECT DOWNLIST OF MEC PREFLIGHT BITE READ DATA          
 _____________________________________________________________________
  DESCRIPTION:                                                        
     C. THE SECOND OPERATOR (OP CODE 3, 8, 11, 17, 18, 19, OR 20)     
        REQUESTS I/O FOR A BTU ADDRESS THAT'S THE OPPOSITE OF THE     
        FIRST OPERATOR, AND THIS SECOND OPERATOR IS PROCESSED BEFORE  
        THE FIRST OPERATOR'S RESPONSE IS FORMATTED (AN "OPPOSITE" BTU 
        ADDRESS IN THIS CASE MEANS IF THE FIRST COMMAND REQUESTED A   
        BTU ADDRESS OF 18, THE SECOND COMMAND SET IT TO ANYTHING      
        OTHER THAN 18; IF THE FIRST COMMAND REQUESTED A BTU ADDRESS   
        OF 20, THE SECOND COMMAND SET IT TO 18).                      
     D. SINCE THE BTU ADDRESS WAS MODIFIED BEFORE THE RESPONSE WAS    
        COMPLETED, THE MEC PREFLIGHT BITE DATA IS PLACED IN THE       
        WRONG MEC D/L BUFFER.                                         
                                                                      
  2) A. SAME AS 1A.                                                   
     B. SAME AS 1B EXCEPT THE FIRST COMMAND IS A TCS MEC CMD (OTHER   
        THAN FIRE 2/FIRE 3) WITH THE READ-BITE-AFTER OPTION SELECTED; 
     C. SAME AS 1C.                                                   
     D. SAME AS 1D.                                                   
                                                                      
  3) THE USER EXECUTES A TCS MEC CMD FIRE 2/FIRE 3 COMMAND WITH THE   
     READ-BITE-AFTER OPTION SELECTED.  IN THIS CASE THE PREFLIGHT     
     BITE DATA FROM THE READ-BITE-AFTER COMMAND WILL ALWAYS BE PLACED 
     IN THE MEC 2 D/L BUFFER UNLESS A PREVIOUSLY EXECUTED TCS I/O     
     COMMAND (OPERATOR CODES 3, 8, 11, 17, 18, 19, OR 20, EXCLUDING   
     MEC FIRE 2/FIRE 3) WAS FOR MEC 1 (BTU ADDR=18), IN WHICH CASE    
     THE PREFLIGHT BITE DATA WILL BE PLACED IN THE MEC 1 D/L BUFFER.  
 _____________________________________________________________________
  USER RESPONSE:                                                      
                                                                      
   2) INSTEAD OF EXECUTING MULTIPLE TCS COMMANDS SIMULTANEOUSLY, THE  
      USER COULD ENSURE THEIR TCS COMMANDS ARE ACTIVE FROM ONLY ONE   
      SOURCE AT A TIME (I.E., TCS-1 ONLY, OR ONLY ONE TCS-S).  MEC    
      PREFLIGHT BITE D/L DATA FOR MEC READS AND MEC CMDS (OTHER THAN  
      FIRE 2/FIRE 3) IS CORRECT IF TCS COMMANDS ARE ACTIVE FROM ONLY  
      ONE SOURCE.                                                     
                                                                      
   FOR THE THIRD SCENARIO THE USER SHOULD RELY SOLELY ON THE LDB DATA 
   (THE D/L DATA IS TOO UNPREDICTABLE UNDER THESE CIRCUMSTANCES AND   
   SHOULD NOT BE USED).                                               
                                                                      
                                                                      
                                                                      
 _____________________________________________________________________
 @
