Sound: BDlab19

       Name: BDlab19                                                 [Show more]
       Type: Subroutine
   Category: Sound
    Summary: Increment the music data pointer in BDdataptr1(1 0) and fetch the
             next data byte into A
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * BDirqhere calls BDlab19
             * BDlab3 calls BDlab19
             * BDlab5 calls BDlab19
             * BDlab7 calls BDlab19
             * BDRO10 calls BDlab19
             * BDRO12 calls BDlab19
             * BDRO13 calls BDlab19
             * BDRO14 calls BDlab19
             * BDRO7 calls BDlab19


 Arguments:

   Y                    Y is always 0


 Returns:

   BDdataptr1(1 0)      Incremented to point to the next music data byte

   A                    The next music data byte


.BDlab19

 INC BDdataptr1         ; Increment the data pointer in BDdataptr1(1 0)
 BNE BDskipme1
 INC BDdataptr1+1

.BDskipme1

 LDA (BDdataptr1),Y     ; Y is zero, so this sets A to the next byte of music
                        ; data from BDdataptr1(1 0)
                        ;
                        ; We have to include an index of Y as the 6502 doesn't
                        ; have an instruction of the form LDA (BDdataptr1)

 RTS                    ; Return from the subroutine