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⌂ ∞ ▽ Elite on the 6502

Version analysis of BEGIN

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

Code variations between these versions are shown below.

       Name: BEGIN
       Type: Subroutine
   Category: Loader
    Summary: Initialise the configuration variables and start the game



.BEGIN

Code variation 1 of 4Specific to an individual platform

This variation is blank in the Master version.

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

Docked
6502SP
 JSR BRKBK              \ Call BRKBK to set BRKV to point to the BRBR routine

\JSR BRKBK              \ This instruction is commented out in the original
                        \ source

Code variation 2 of 4Specific to an individual platform

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

Docked, 6502SP
Master
 LDX #(CATF-COMC)       \ We start by zeroing all the configuration variables
                        \ between COMC and CATF, to set them to their default
                        \ values, so set a counter in X for CATF - COMC bytes

 LDX #(DISK-COMC)       \ We start by zeroing all the configuration variables
                        \ between COMC and DISK, to set them to their default
                        \ values, so set a counter in X for DISK - COMC bytes

 LDA #0                 \ Set A = 0 so we can zero the variables

.BEL1

 STA COMC,X             \ Zero the X-th configuration variable

 DEX                    \ Decrement the loop counter

 BPL BEL1               \ Loop back to BEL1 to zero the next byte, until we have
                        \ zeroed them all

Code variation 3 of 4Specific to an individual platform

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

6502SP, Master
 LDA XX21+SST*2-2       \ Set spasto(1 0) to the Coriolis space station entry
 STA spasto             \ from the ship blueprint lookup table at XX21 (so
 LDA XX21+SST*2-1       \ spasto(1 0) points to the Coriolis blueprint)
 STA spasto+1

Code variation 4 of 4Related to the Master version

The Master version contains an embedded copy of the default JAMESON commander file that gets loaded on start-up.

This variation is blank in the Disc (docked) and 6502 Second Processor versions.

Master
 JSR JAMESON            \ Call JAMESON to set the last saved commander to the
                        \ default "JAMESON" commander

                        \ Fall through into TT170 to start the game