Sound: BDlab4

       Name: BDlab4                                                  [Show more]
       Type: Subroutine
   Category: Sound
    Summary: Set the voice control register for voice 1 to value1
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * BDRO1 calls BDlab4
             * BDRO4 calls BDlab4
             * BDRO5 calls BDlab4


.BDlab4

 LDA value1             ; Set A to value1, to use as the new value of the voice
                        ; control register for voice 1

 STY SID+$4             ; Zero SID register $4 (the voice control register for
                        ; voice 1), to reset the voice control

 STA SID+$4             ; Set SID register $4 (the voice control register for
                        ; voice 1) to the music data byte that we just fetched
                        ; in A, so control the voice as follows:
                        ;
                        ;   * Bit 0: 0 = voice off, release cycle
                        ;            1 = voice on, attack-decay-sustain cycle
                        ;
                        ;   * Bit 1 set = synchronization enabled
                        ;
                        ;   * Bit 2 set = ring modulation enabled
                        ;
                        ;   * Bit 3 set = disable voice, reset noise generator
                        ;
                        ;   * Bit 4 set = triangle waveform enabled
                        ;
                        ;   * Bit 5 set = saw waveform enabled
                        ;
                        ;   * Bit 6 set = square waveform enabled
                        ;
                        ;   * Bit 7 set = noise waveform enabled

 RTS                    ; Return from the subroutine