The UpdateSaveScreen (Bank 6) subroutine - Elite on the BBC Micro and NES

       Name: UpdateSaveScreen                                        [Show more]
       Type: Subroutine
   Category: Save and load
    Summary: Update the Save and Load screen
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * MoveInMiddleColumn calls UpdateSaveScreen
             * MoveInRightColumn calls UpdateSaveScreen
             * MoveToLeftColumn calls UpdateSaveScreen


 Returns:

   A                    A is preserved


.UpdateSaveScreen

 PHA                    ; Store the value of A on the stack so we can restore it
                        ; at the end of the subroutine

 JSR DrawScreenInNMI_b0 ; Configure the NMI handler to draw the screen

 JSR WaitForPPUToFinish ; Wait until both bitplanes of the screen have been
                        ; sent to the PPU, so the screen is fully updated and
                        ; there is no more data waiting to be sent to the PPU

 PLA                    ; Restore the value of A that we stored on the stack, so
                        ; A is preserved

 RTS                    ; Return from the subroutine

[X]

Subroutine DrawScreenInNMI_b0 (category: Drawing the screen)

Call the DrawScreenInNMI routine in ROM bank 0

[X]

Subroutine WaitForPPUToFinish (category: PPU)

Wait until the NMI handler has finished updating both bitplanes, so the screen is no longer refreshing

Save and load: UpdateSaveScreen

[NES version, Bank 6]