Skip to navigation

⌂ ∞ ▽ Elite on the BBC Micro and NES

Utility routines: WaitForNMI

[NES version, Bank 7]

       Name: WaitForNMI                                              [Show more]
       Type: Subroutine
   Category: Utility routines
    Summary: Wait until the next NMI interrupt has passed (i.e. the next
             VBlank)

    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * CheckSaveSlots calls WaitForNMI
             * ChooseLanguage calls WaitForNMI
             * ChooseMusic_b6 calls WaitForNMI
             * DEATH2 calls WaitForNMI
             * DELAY calls WaitForNMI
             * DrawEquipment calls WaitForNMI
             * EQSHP calls WaitForNMI
             * FadeToBlack calls WaitForNMI
             * FadeToColour calls WaitForNMI
             * FastForwardJump calls WaitForNMI
             * LOOK1 calls WaitForNMI
             * PauseGame calls WaitForNMI
             * ResetMusicAfterNMI calls WaitForNMI
             * ResetStardust calls WaitForNMI
             * SendViewToPPU calls WaitForNMI
             * SetupViewInNMI calls WaitForNMI
             * ShowScrollText calls WaitForNMI
             * TT102 calls WaitForNMI
             * TT110 calls WaitForNMI
             * TT16 calls WaitForNMI
             * TT18 calls WaitForNMI
             * WaitFor2NMIs calls WaitForNMI
             * WARP calls WaitForNMI




 Returns:

   A                    A is preserved



.WaitForNMI

 PHA                    ; Store A on the stack to preserve it

 LDX nmiCounter         ; Set X to the NMI counter, which increments with each
                        ; call to the NMI handler

.wnmi1

 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

 CPX nmiCounter         ; Loop back to wnmi1 until the NMI counter changes,
 BEQ wnmi1              ; which will happen when the NMI handler has been called
                        ; again (i.e. at the next VBlank)

 PLA                    ; Retrieve A from the stack so that it's preserved

 RTS                    ; Return from the subroutine