Version analysis of BR1 (Part 2 of 2) - Elite on the BBC Micro and NES

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

Cassette, Disc (docked), 6502 Second Processor, Master and Electron

Code variations between these versions are shown below.

       Name: BR1 (Part 2 of 2)
       Type: Subroutine
   Category: Start and end
    Summary: Show the "Press Fire or Space, Commander" screen and start the
             game


 BRKV is set to point to BR1 by the loading process.


 JSR msblob             \ Reset the dashboard's missile indicators so none of
                        \ them are targeted

Code variation 1 of 2Related to a standard feature

On the second title page (the one that says "Press Space Or Fire,Commander"), the cassette and Electron versions show a rotating Mamba, the disc version shows a rotating Krait, the 6502SP version shows a rotating Asp Mk II, and the Master version shows a rotating Cougar.

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

Cassette, Electron
Docked
Master
6502SP
 LDA #147               \ Call TITLE to show a rotating Mamba (#3) and token
 LDX #3                 \ 147 ("PRESS FIRE OR SPACE,COMMANDER.{crlf}{crlf}"),
 JSR TITLE              \ returning with the internal number of the key pressed
                        \ in A
 LDA #7                 \ Call TITLE to show a rotating Krait (#KRA) and token
 LDX #KRA               \ 7 ("PRESS SPACE OR FIRE,{single cap}COMMANDER.{cr}
 JSR TITLE              \ {cr}"), returning with the internal number of the key
                        \ pressed in A
 LDA #7                 \ Call TITLE to show a rotating Cougar (#COU) and token
 LDX #COU               \ 7 ("PRESS SPACE OR FIRE,{single cap}COMMANDER.{cr}
 LDY #100               \ {cr}"), with the ship at a distance of 100, returning
 JSR TITLE              \ with the internal number of the key pressed in A
 LDA #7                 \ Call TITLE to show a rotating Asp Mk II (#ASP) and
 LDX #ASP               \ token 7 ("PRESS SPACE OR FIRE,{single cap}COMMANDER.
 JSR TITLE              \ {cr}{cr}"), returning with the internal number of the
                        \ key pressed in A

 JSR ping               \ Set the target system coordinates (QQ9, QQ10) to the
                        \ current system coordinates (QQ0, QQ1) we just loaded

Code variation 2 of 2Specific to an individual platform

The 6502SP version inlines the code from the hyp1 routine here, instead of calling it (though it could just as easily call it, as the hyp1 routine is included in the 6502SP version and contains the same code).

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

Cassette, Docked, Electron
6502SP, Master
 JSR hyp1               \ Arrive in the system closest to (QQ9, QQ10)
 JSR TT111              \ Select the system closest to galactic coordinates
                        \ (QQ9, QQ10)

 JSR jmp                \ Set the current system to the selected system

 LDX #5                 \ We now want to copy the seeds for the selected system
                        \ in QQ15 into QQ2, where we store the seeds for the
                        \ current system, so set up a counter in X for copying
                        \ 6 bytes (for three 16-bit seeds)

                        \ The label below is called likeTT112 because this code
                        \ is almost identical to the TT112 loop in the hyp1
                        \ routine

.likeTT112

 LDA QQ15,X             \ Copy the X-th byte in QQ15 to the X-th byte in QQ2
 STA QQ2,X

 DEX                    \ Decrement the counter

 BPL likeTT112          \ Loop back to likeTT112 if we still have more bytes to
                        \ copy

 INX                    \ Set X = 0 (as we ended the above loop with X = &FF)

 STX EV                 \ Set EV, the extra vessels spawning counter, to 0, as
                        \ we are entering a new system with no extra vessels
                        \ spawned

 LDA QQ3                \ Set the current system's economy in QQ28 to the
 STA QQ28               \ selected system's economy from QQ3

 LDA QQ5                \ Set the current system's tech level in tek to the
 STA tek                \ selected system's economy from QQ5

 LDA QQ4                \ Set the current system's government in gov to the
 STA gov                \ selected system's government from QQ4

                        \ Fall through into the docking bay routine below