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⌂ ∞ ▽ Elite on the 6502

Flight: ChargeShields

[NES version, Bank 0]

       Name: ChargeShields                                           [Show more]
       Type: Subroutine
   Category: Flight
    Summary: Charge the shields and energy banks

    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * InSystemJump calls ChargeShields
             * Main flight loop (Part 13 of 16) calls ChargeShields




.ChargeShields

 SETUP_PPU_FOR_ICON_BAR ; If the PPU has started drawing the icon bar, configure
                        ; the PPU to use nametable 0 and pattern table 0

 LDX ENERGY             ; Fetch our ship's energy levels and skip to b if bit 7
 BPL b                  ; is not set, i.e. only charge the shields from the
                        ; energy banks if they are at more than 50% charge

 LDX ASH                ; Call SHD to recharge our aft shield and update the
 JSR SHD                ; shield status in ASH
 STX ASH

 LDX FSH                ; Call SHD to recharge our forward shield and update
 JSR SHD                ; the shield status in FSH
 STX FSH

.b

 SEC                    ; Set A = ENERGY + ENGY + 1, so our ship's energy
 LDA ENGY               ; level goes up by 2 if we have an energy unit fitted,
 ADC ENERGY             ; otherwise it goes up by 1

 BCS paen1              ; If the value of A did not overflow (the maximum
 STA ENERGY             ; energy level is $FF), then store A in ENERGY

.paen1

 RTS                    ; Return from the subroutine