Initial Creativision Import

libsrc/creativision/psg.s

@@ -0,0 +1,68 @@
+; void __fastcall__ psg_outb( unsigned char b );
+; void __fastcall__ psg_delayms( unsigned char c);
+; void __fastcall__ bios_playsound( void *b, unsigned char c);
+; void psg_silence( void );
+
+    .export     _psg_outb, _psg_silence, _psg_delay
+    .export     _bios_playsound
+    .import     popa
+    .include    "creativision.inc"
+    
+_psg_outb:
+
+    ;* Let BIOS output the value
+    jmp $FE77
+    
+_psg_silence:
+
+    jmp $FE54
+    
+    
+_psg_delay:
+
+    tay
+l1:     
+    lda #200
+l2:
+    sbc #1
+    bne l2
+    
+    lda #200
+l3:
+    sbc #1
+    bne l3
+    
+    dey
+    bne l1
+    
+    rts
+    
+
+;* Creativision Sound Player
+;*
+;* Based on BIOS sound player.
+;* Pass a pointer to a set of note triples, terminated with a tempo byte
+;* and the len (max 255)
+
+_bios_playsound:
+
+    pha                 ; Save Length Byte
+    
+    sei
+        
+    lda         #$D5    ; BIOS volume table low
+    sta         $4
+    lda         #$FC    ; BIOS volume table high
+    sta         $5
+    
+    jsr         popa    ; Get Sound table pointer low
+    sta         $0
+    jsr         popa    ; Get Sound table pointer high
+    sta         $1
+    
+    pla
+    tay                 ; Put length in Y
+    dey
+    php
+    jmp         $fbed   ; Let BIOS do it's thing
+