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⌂ ∞ Elite on the BBC Micro and NES

PPU: UpdateScreen

[NES version, Bank 7]

       Name: UpdateScreen                                            [Show more]
       Type: Subroutine
   Category: PPU
    Summary: Update the screen by sending data to the PPU, either immediately
             or during VBlank, depending on whether the screen is visible
  Deep dive: Views and view types in NES Elite

    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * ChangeToView calls UpdateScreen
             * UpdateHangarView calls UpdateScreen
             * UpdateView calls UpdateScreen




.UpdateScreen

 LDA screenFadedToBlack ; If bit 7 of screenFadedToBlack is clear then the
 BPL SetupFullViewInNMI ; screen is visible and has not been faded to black, so
                        ; we need to send the view to the PPU in the NMI handler
                        ; to avoid corrupting the screen, so jump to
                        ; SetupFullViewInNMI to configure the NMI handler
                        ; accordingly

                        ; Otherwise the screen has been faded to black, so we
                        ; can fall through into SendViewToPPU to send the view
                        ; straight to the PPU without having to restrict
                        ; ourselves to VBlank