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⌂ ∞ ▽ Elite on the 6502

Demo: VCSUB

[Elite Demonstration Disc]

       Name: VCSUB                                                   [Show more]
       Type: Subroutine
   Category: Demo
    Summary: Calculate vector K3(8 0) = [x y z] - coordinates in (A V)

    Context: See this subroutine in context in the source code
 References: No direct references to this subroutine in this source file




 Calculate the following:

   K3(2 1 0) = (x_sign x_hi x_lo) - x-coordinate in (A V)

   K3(5 4 3) = (y_sign y_hi z_lo) - y-coordinate in (A V)

   K3(8 7 6) = (z_sign z_hi z_lo) - z-coordinate in (A V)

 where the first coordinate is from the ship data block in INWK, and the second
 coordinate is from the ship data block pointed to by (A V).

 This routine has been copied from the disc version of Elite.



                        \ --- Mod: Code added for Demonstration Disc: --------->

.VCSUB

 STA V+1                \ Set the low byte of V(1 0) to A, so now V(1 0) = (A V)

 LDY #2                 \ K3(2 1 0) = (x_sign x_hi x_lo) - x-coordinate in data
 JSR TAS1               \ block at V(1 0)

 LDY #5                 \ K3(5 4 3) = (y_sign y_hi z_lo) - y-coordinate of data
 JSR TAS1               \ block at V(1 0)

 LDY #8                 \ Fall through into TAS1 to calculate the final result:
                        \
                        \ K3(8 7 6) = (z_sign z_hi z_lo) - z-coordinate of data
                        \ block at V(1 0)

                        \ --- End of added code ------------------------------->