Utility routines: ResetVariable

       Name: ResetVariable                                           [Show more]
       Type: Subroutine
   Category: Utility routines
    Summary: Set a 16-bit in the variable workspace to 0
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * ApplyFlightModel (Part 5 of 7) calls ResetVariable
             * ProcessLanding (Part 2 of 7) calls ResetVariable
             * ProcessLanding (Part 3 of 7) calls ResetVariable
             * ProcessLanding (Part 4 of 7) calls ResetVariable
             * ProcessLanding (Part 7 of 7) calls ResetVariable


 Arguments:

   X                    The offset from xTurnHi of the low byte of the variable
                        to zero:

                          * &00 = xTurn(Top Hi)
                          * &02 = zTurn(Top Hi)
                          * &80 = dxTurn(Top Hi)
                          * &82 = dzTurn(Top Hi)
                          * &8A = yVelocity(Top Hi)
                          * &EA = xRotation(Hi Lo)
                          * &EC = zRotation(Hi Lo)
                          * &EE = yPlane(Hi Lo)

                        In the case of the two 24-bit variables, X is the offset
                        of the high byte, and we have to zero the low byte
                        manually after the routine call


 Returns:

   A                    A is set to 0


.ResetVariable

 LDA #0                 \ Zero the X-th byte from xTurnHi
 STA xTurnHi,X

 STA xTurnTop,X         \ Zero the X-th byte from xTurnTop

 RTS                    \ Return from the subroutine