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⌂ ∞ ▽ Elite on the 6502

Version analysis of PAS1

This code appears in the following versions (click to see it in the source code):

Code variations between these versions are shown below.

       Name: PAS1
       Type: Subroutine
   Category: Missions

Code variation 1 of 4A variation in the comments only

This variation is blank in the Master version.

Docked, 6502SP
    Summary: Display a rotating ship at space coordinates (0, 112, 256) and
             scan the keyboard

Code variation 2 of 4A variation in the comments only

Tap on a block to expand it, and tap it again to revert.

Docked, 6502SP
Master
 Returns:

   X                    If a key is being pressed, X contains the internal key
                        number, otherwise it contains 0

   A                    Contains the same as X

 Returns:

   X                    If a key is being pressed, X contains the ASCII code of
                        the key being pressed, otherwise it contains 0

   A                    Contains the same as X


.PAS1

Code variation 3 of 4Related to the Master version

In the Master version, the rotating Constrictor in the mission 1 briefing is slightly higher up the screen than in the other versions.

This variation is blank in the Master version.

Docked, 6502SP
 LDA #112               \ Set y_lo = 112
 STA INWK+3

 LDA #0                 \ Set x_lo = 0
 STA INWK

 STA INWK+6             \ Set z_lo = 0

 LDA #2                 \ Set z_hi = 1, so (z_hi z_lo) = 256
 STA INWK+7

 JSR LL9                \ Draw the ship on screen

 JSR MVEIT              \ Call MVEIT to move and rotate the ship in space

Code variation 4 of 4Specific to an individual platform

Tap on a block to expand it, and tap it again to revert.

Docked, 6502SP
Master
 JMP RDKEY              \ Scan the keyboard for a key press and return the
                        \ internal key number in X (or 0 for no key press),
                        \ returning from the subroutine using a tail call

 JMP RDKEY              \ Scan the keyboard for a key press and return the
                        \ ASCII code of the key pressed in X (or 0 for no key
                        \ press), returning from the subroutine using a tail
                        \ call