The SOUL3b subroutine - Elite on the 6502

       Name: SOUL3b                                                  [Show more]
       Type: Subroutine
   Category: Sound
    Summary: Check whether this is the last voice when making sound effects in
             the interrupt routine, and return from the interrupt if it is
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * SOINT calls SOUL3b


 Arguments:

   Y                    The voice number that is currently being processed in
                        the interrupt routine at SOINT (0 to 2)


.SOUL3b

 DEY                    ; Decrement the voice number

 BPL SOUL8              ; If we have not yet processed all three voices then Y
                        ; will still be positive (i.e. 0, 1 or 2), so jump to
                        ; SOUL8 to process this voice

                        ; If we get here then we have processed all three voices
                        ; in the sound effects interrupt routine, so we now need
                        ; to return from the interrupt

 PLA                    ; Retrieve the value of Y we stored on the stack at the
 TAY                    ; start of the music section of the interrupt routine,
                        ; so it is preserved

                        ; Fall through into COMIRQ3 to restore the A and X
                        ; registers and the correct memory configuration, and
                        ; return from the interrupt
Sound: SOUL3b

[Commodore 64 version]
