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⌂ ∞ Elite on the BBC Micro and NES

Sound: StartEffect

[NES version, Bank 6]

       Name: StartEffect                                             [Show more]
       Type: Subroutine
   Category: Sound
    Summary: Start making a sound effect on the specified 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:
             * StartEffect_b6 calls StartEffect




 Arguments:

   A                    The number of the sound effect to make

   X                    The sound channel on which to make the sound effect:

                          * 0 = SQ1

                          * 1 = SQ2

                          * 2 = NOISE



.StartEffect

 DEX                    ; Decrement the channel number in X, so we can check the
                        ; value in the following tests

 BMI msef1              ; If X is now negative then the channel number must be
                        ; 0, so jump to msef1 to make the sound effect on the
                        ; SQ1 channel

 BEQ StartEffectOnSQ2   ; If X is now zero then the channel number must be 1, so
                        ; jump to StartEffectOnSQ2 to start making the sound
                        ; effect on the SQ2 channel, returning from the
                        ; subroutine using a tail call

 JMP StartEffectOnNOISE ; Otherwise the channel number must be 2, so jump to
                        ; StartEffectOnNOISE to make the sound effect on the
                        ; NOISE channel, returning from the subroutine using a
                        ; tail call

.msef1

 JMP StartEffectOnSQ1   ; Jump to StartEffectOnSQ1 to start making the sound
                        ; effect on the SQ1 channel, returning from the
                        ; subroutine using a tail call