; #+0000     GP_00           usually used as a two-byte pointer for indirection
; #+0001     GP_01
; #+0002     GP_02           often used as a two-byte counter
; #+0003     GP_03  

; #+005C     FlipFlag        non zero to cause interrupt to flip name tables

; #+0066     SND_PtrA        pointer to current music
; #+0067     SND_PtrB        pointer to current music

; #+006A     SND_Sq1Fine     current value of square 1 fine
; #+006B     SND_Sq2Fine     current value of square 2 fine


; #+006D     MusEffBell      mussic effect envelope counter
; #+006E     MusEffRel       music effect count reload
; #+006F     MusEffCnt       music effect current count

; #+00F5     UNKNOWN_F5      filled with 5A after all sets copied to VRAM
; #+00FE     CUR_2001        current contents of PPU 2001 (a write-only register)
; #+00FF     CUR_2000        current contents of PPU 2000 (a write-only register)

; #+05F0     TriFine         current value of triangle fine

; #+051D     UNKNOWN_051D    used as a "set pointer" to index multiple data blocks to copy to VRAM

; #+05F5     SND_DrumRep     ?? point to start of drum track for repeat

; #+0600     SND_ReqMusic    Request song
; #+0601     SND_601         ?? something to do with sound
; #+0602     SND_ReqMusEff   Music effect request (long music continues to play)
; #+0603     SND_603         ?? something to do with sound
; #+0604     SND_Request     Sound effect request (near-death-beep will not preempt another sound)
; #+0605     SND_CurEffect   current playing sound effect

; #+0607     SND_CurMusEff   current playing music effect
; #+0608     SND_DMod1       parameter in delta-mod effect
; #+0609     SND_CurSong     current playing song

; #+060A     SND_SongPC_A    offset within current song for voice A
; #+060B     SND_SongPC_B    offset within current song for voice B
; #+060C     SND_SongPC_C    offset within current song for voice C
; #+060D     SND_SongPC_D    offset within current song for voice D

; #+0610     SND_LenReload   music event timer reload
; #+0611     SND_Timer       music event timer

; #+0618     SND_MusEffDel   script pointer for music effect

; Battery-Backed RAM

; #+6001    MARK_A           must be 5A for ram to be valid
; #+652A    Q_SG1            ?? save-game 1 flag? set to FF if BBR is not valid
; #+652B    Q_SG2            ?? save-game 2 flag? set to FF if BBR is not valid
; #+652C    Q_SQ3            ?? save-game 3 flag? set to FF if BBR is not valid

; 6530-7FFF cleared on startup if BBR is not valid

; #+7FFF    MARK_B           must be 5A for ram to be valid



; TOPHER-temp Music descriptor
;00 -> Note delay set (0-4)
;01    -> Pointer to Music
;02    -> ...
;03 -> Offset for C (A begins at 0)
;04 -> Offset for B
;05 -> Offset for D
;06 -> 0619
;07 -> 05F1