Screen mode: KillCustomScreen

       Name: KillCustomScreen                                        [Show more]
       Type: Subroutine
   Category: Screen mode
    Summary: Disable the custom screen mode and switch to mode 7
  Deep dive: Hidden secrets of the custom screen mode
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * MainDrivingLoop (Part 5 of 5) calls KillCustomScreen


.KillCustomScreen

 SEI                    \ Disable interrupts so we can update the interrupt
                        \ vector and VIA

 LDA irq1Address        \ Set the IRQ1V vector to irq1Address, which removes the
 STA IRQ1V              \ custom screen interrupt handler from the chain
 LDA irq1Address+1
 STA IRQ1V+1

 LDA #%01000000         \ Set 6522 User VIA interrupt enable register IER
 STA VIA+&6E            \ (SHEILA &4E) bit 6 (i.e. disable the Timer1 interrupt
                        \ from the User VIA, as we no longer need it)

 CLI                    \ Re-enable interrupts

 JSR FlushSoundBuffers  \ Flush all four sound channel buffers

                        \ Fall through into SetScreenMode7 to switch to mode 7