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⌂ ∞ Elite on the BBC Micro and NES

Version analysis of MVEIT (Part 9 of 9)

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

Code variations between these versions are shown below.

       Name: MVEIT (Part 9 of 9)
       Type: Subroutine
   Category: Moving
    Summary: Move current ship: Redraw on scanner, if it hasn't been destroyed



 This routine has multiple stages. This stage does the following:

   * If the ship is exploding or being removed, hide it on the scanner

   * Otherwise redraw the ship on the scanner, now that it's been moved



.MV5

 LDA INWK+31            \ Fetch the ship's exploding/killed state from byte #31

Code variation 1 of 2Specific to an individual platform

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

Cassette, Flight, 6502SP, Master, Electron
Docked
 AND #%10100000         \ If we are exploding or removing this ship then jump to
 BNE MVD1               \ MVD1 to remove it from the scanner permanently

 AND #%00100000         \ If we are exploding then jump to MVD1 to remove it
 BNE MVD1               \ from the scanner permanently

 LDA INWK+31            \ Set bit 4 to keep the ship visible on the scanner
 ORA #%00010000
 STA INWK+31

Code variation 2 of 2Specific to an individual platform

This variation is blank in the Disc (docked) version.

Cassette, Flight, 6502SP, Master, Electron
 JMP SCAN               \ Display the ship on the scanner, returning from the
                        \ subroutine using a tail call

.MVD1

 LDA INWK+31            \ Clear bit 4 to hide the ship on the scanner
 AND #%11101111
 STA INWK+31

 RTS                    \ Return from the subroutine