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⌂ ∞ ▽ Elite on the 6502

Dashboard: WPSHPS

[NES version, Bank 0]

       Name: WPSHPS                                                  [Show more]
       Type: Subroutine
   Category: Dashboard
    Summary: Set all ships to be hidden from the screen

    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * NWSTARS calls WPSHPS
             * RES2 calls WPSHPS




.WPSHPS

 LDX #0                 ; Set up a counter in X to work our way through all the
                        ; ship slots in FRIN

.WSL1

 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

 LDA FRIN,X             ; Fetch the ship type in slot X

 BEQ WS2                ; If the slot contains 0 then it is empty and we have
                        ; checked all the slots (as they are always shuffled
                        ; down in the main loop to close up and gaps), so jump
                        ; to WS2 as we are done

 BMI WS1                ; If the slot contains a ship type with bit 7 set, then
                        ; it contains the planet or the sun, so jump down to WS1
                        ; to skip this slot, as the planet and sun don't appear
                        ; on the scanner

 STA TYPE               ; Store the ship type in TYPE

 JSR GINF               ; Call GINF to get the address of the data block for
                        ; ship slot X and store it in INF

 LDY #31                ; Clear bits 3 and 6 in the ship's byte #31, which stops
 LDA (INF),Y            ; drawing the ship on-screen (bit 3), and denotes that
 AND #%10110111         ; the explosion has not been drawn and there are no
 STA (INF),Y            ; lasers firing (bit 6)

.WS1

 INX                    ; Increment X to point to the next ship slot

 BNE WSL1               ; Loop back up to process the next slot (this BNE is
                        ; effectively a JMP as X will never be zero)

.WS2

 LDX #0                 ; Set X = 0 (though this appears not to be used)

 RTS                    ; Return from the subroutine