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⌂ ∞ ▽ Elite on the 6502

Start and end: RESET

[Elite-A, Docked]

       Name: RESET                                                   [Show more]
       Type: Subroutine
   Category: Start and end
    Summary: Reset most variables

    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * TITLE calls RESET




 Reset our ship and various controls, recharge shields and energy, and then
 fall through into RES2 to reset the stardust and the ship workspace at INWK.

 In this subroutine, this means zero-filling the following locations:

   * Pages &9, &A, &B, &C and &D

   * BETA to BETA+8, which covers the following:

     * BETA, BET1 - Set pitch to 0

     * XC, YC - Set text cursor to (0, 0)

     * QQ22 - Set hyperspace counters to 0

     * ECMA - Turn E.C.M. off

     * ALP1, ALP2 - Set roll signs to 0

 It also sets QQ12 to &FF, to indicate we are docked, recharges the shields and
 energy banks, and then falls through into RES2.



.RESET

 JSR ZERO               \ Zero-fill pages &9, &A, &B, &C and &D, which clears
                        \ the ship data blocks, the ship line heap, the ship
                        \ slots for the local bubble of universe, and various
                        \ flight and ship status variables

 LDX #6                 \ Set up a counter for zeroing BETA through BETA+6

.SAL3

 STA BETA,X             \ Zero the X-th byte after BETA

 DEX                    \ Decrement the loop counter

 BPL SAL3               \ Loop back for the next byte to zero

 TXA                    \ X is now negative - i.e. &FF - so this sets A and QQ12
 STA QQ12               \ to &FF to indicate we are docked

 LDX #2                 \ We're now going to recharge both shields and the
                        \ energy bank, which live in the three bytes at FSH,
                        \ ASH (FSH+1) and ENERGY (FSH+2), so set a loop counter
                        \ in X for 3 bytes

.REL5

 STA FSH,X              \ Set the X-th byte of FSH to &FF to charge up that
                        \ shield/bank

 DEX                    \ Decrement the loop counter

 BPL REL5               \ Loop back to REL5 until we have recharged both shields
                        \ and the energy bank

                        \ Fall through into RES2 to reset the stardust and ship
                        \ workspace at INWK