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⌂ ∞ Elite on the BBC Micro and NES

Sound: FlushSoundChannel

[NES version, Bank 7]

       Name: FlushSoundChannel                                       [Show more]
       Type: Subroutine
   Category: Sound
    Summary: Flush a specific sound channel
  Deep dive: Sound effects in NES Elite

    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * FlushSoundChannels calls FlushSoundChannel
             * FlushSpecificSound calls FlushSoundChannel
             * FlushSQ2AndNOISE calls FlushSoundChannel




 Arguments:

   X                    The sound channel to flush:

                          * 0 = flush the SQ1 sound channel

                          * 1 = flush the SQ2 sound channel

                          * 2 = flush the NOISE sound channel



.FlushSoundChannel

 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 #0                 ; Set the priority for channel X to zero to stop the
 STA channelPriority,X  ; channel from making any more sounds

 LDA #26                ; Set A = 26 to pass to StartEffect below (sound effect
                        ; 26 is the sound of silence, so this flushes the sound
                        ; channel)

 BNE StartEffect_b7     ; Jump to StartEffect to start making sound effect 26
                        ; on channel X (this BNE is effectively a JMP as A is
                        ; never zero)