6502 command stream player, part 2

src/asm/6502/stream.s

@@ -18,6 +18,7 @@ FCS_MAX_STACK=16 ; stack depth per channel (FCS_MAX_STACK*FCS_MAX_CHAN<256)
 
 ; player constants - change if necessary
 fcsAddrBase=$20 ; player state address base
+fcsZeroPage=$10 ; player state address base for zero-page-mandatory variables
 fcsGlobalStack=$200 ; player stack (best placed in a page)
 fcsPtr=$8000 ; pointer to command stream
 fcsVolMax=fcsVolMaxExample ; pointer to max channel volume array
@@ -31,7 +32,8 @@ fcsSpeedDial=fcsPtr+24
 ;   - do not implement HINT commands - the player will never send these
 ;   - no need to implement commands not pertaining to the target system
 ; - a zero pointer means "don't handle"
-fcsCmdTable=fcsCmdTableExample
+fcsCmdTableLow=fcsCmdTableExample
+fcsCmdTableHigh=fcsCmdTableExample
 
 ; variables
 ; these may be read by your command handling routines
@@ -42,25 +44,107 @@ fcsTicks=fcsAddrBase+8 ; short
 ; temporary variables
 fcsSendVolume=fcsAddrBase+10 ; char
 fcsSendPitch=fcsAddrBase+11 ; char
+fcsCmd=fcsAddrBase+16 ; char[8]
+fcsTempPtr=fcsZeroPage ; short
 ; channel state
-chanPC=fcsAddrBase+16 ; short
-chanTicks=fcsAddrBase+16+(FCS_MAX_CHAN*2) ; short
-chanStackPtr=fcsAddrBase+16+(FCS_MAX_CHAN*4) ; char
+chanPC=fcsZeroPage+2 ; short
+chanTicks=fcsAddrBase+24 ; short
+chanStackPtr=fcsAddrBase+24+(FCS_MAX_CHAN*2) ; char
+chanNote=fcsAddrBase+24+(FCS_MAX_CHAN*2)+1 ; char
+chanVibratoPos=fcsAddrBase+24+(FCS_MAX_CHAN*4) ; char
 
 ; may be used for driver detection
 fcsDriverInfo:
   .byte "Furnace"
   .byte 0
 
+; note on null
+fcsNoteOnNull:
+  lda #0
+  sta chanVibratoPos,x
+  jsr fcsDispatchCmd
+  rts
+
+; note off, note off env, env release
+fcsNoArgDispatch:
+  jsr fcsDispatchCmd
+  rts
+
+fcsOneByteDispatch:
+  tya
+  pha
+  jsr fcsReadNext
+  sta fcsArg0
+  pla
+  tay
+  jsr fcsDispatchCmd
+  rts
+
+; x: channel*2
+; y: command
+fcsDispatchCmd:
+  ; read command call table
+  lda fcsCmdTableLow,y
+  sta fcsTempPtr
+  lda fcsCmdTableHigh,y
+  sta fcsTempPtr+1
+  ; check for zero
+  lda fcsTempPtr
+  ora fcsTempPtr
+  beq :+ ; get out
+  ; handle command in dispatch code
+  jmp (fcsTempPtr)
+  ; only if pointer is zero
+: rts
+
+; x: channel*2
+; a is set to next byte
+fcsReadNext:
+  lda chanPC+1,x
+  sta fcsTempPtr+1
+
+  ldy chanPC,x
+  lda (fcsTempPtr),y
+  iny
+  bne :+
+  inc chanPC+1,x
+: sty chanPC,x
+  rts
+
 ; x: channel*2 (for speed... char variables are interleaved)
 ; read commands
 fcsChannelCmd:
   ; read next byte
+  jsr fcsReadNext
 
   ; process and read arguments
+  ; if (a<0xb3)
+  bmi fcsNote ; handle $00-$7f
+  cmp #$b3
+  bpl fcsOther
 
-  ; end
-  rts
+  ; this is a note
+  fcsNote:
+    sta fcsArg0
+    sta chanNote,x
+    lda #0
+    tay
+    sta chanVibratoPos,x
+    ; call DIV_CMD_NOTE_ON
+    jsr fcsDispatchCmd
+    rts
+
+  ; other instructions
+  fcsOther:
+    ; call respective handler
+    sec
+    sbc #$b4
+    tay
+    lda fcsInsTableLow,y
+    sta fcsTempPtr
+    lda fcsInsTableHigh,y
+    sta fcsTempPtr+1
+    jmp (fcsTempPtr)
 
 ; x: channel*2
 ; stuff that goes after command reading
@@ -132,7 +216,7 @@ fcsTick:
   inc fcsTicks
   bne :+
   inc fcsTicks+1
-  
+
   ; end
 : rts
 
@@ -140,18 +224,18 @@ fcsInit:
   ; set all tick counters to 1
   lda #1
   ldy #0
-  ldx #(FCS_MAX_CHANS*2)-1
-: sty fcsTicks,x
-  dex
-  sta fcsTicks,x
+  ldx #(FCS_MAX_CHANS*2)
+: dex
+  sty chanTicks,x
   dex
+  sta chanTicks,x
   bne :-
 
   ; set channel program counters
-  ldx #(FCS_MAX_CHANS*2)-1
-: lda fcsPtr+40,x
+  ldx #(FCS_MAX_CHANS*2)
+: dex
+  lda fcsPtr+40,x
   sta chanPC,x
-  dex
   bne :-
 
   ; TODO: relocate and more...