Preparation for audio support - sound queues.

applecorn.s

@@ -198,6 +198,7 @@ MAINZP      MAC
             PUT   AUXMEM.BYTWRD
             PUT   AUXMEM.CHARIO
             PUT   AUXMEM.MISC
+            PUT   AUXMEM.AUDIO
 
 * Automatically save the object file:
             SAV   APPLECORN

auxmem.audio.s

@@ -0,0 +1,64 @@
+* AUXMEM.AUDIO.S
+* (c) Bobbi 2022 GPLv3
+*
+* Applecorn audio code
+*
+
+SNDBUFSZ   EQU   16                          ; All audio buffers are 16 bytes
+
+* Get address of sound buffer
+* On entry: X is buffer number
+* On exit: OSIRQWS points to start of buffer
+* Called with interrupts disabled
+GETBUFADDR  LDA   :BUFADDRL,X
+            STA   OSINTWS+0
+            LDA   :BUFADDRH,X
+            STA   OSINTWS+1
+            RTS
+:BUFADDRL   DB    $00
+            DB    $00
+            DB    $00
+            DB    $00
+            DB    <SNDBUF0
+            DB    <SNDBUF1
+            DB    <SNDBUF2
+            DB    <SNDBUF3
+            DB    $00
+:BUFADDRH   DB    $00
+            DB    $00
+            DB    $00
+            DB    $00
+            DB    >SNDBUF0
+            DB    >SNDBUF1
+            DB    >SNDBUF2
+            DB    >SNDBUF3
+            DB    $00
+
+
+* Insert value into buffer (INSV)
+* On entry: A is value, X is buffer number.
+* On exit: A, X preserved. C clear on success.
+INSHND      PHP                              ; Save flags, turn off interrupts
+            SEI
+            PHA
+            LDY   ENDINDICES,X               ; Get input pointer
+            INY                              ; Next byte
+            CPY   #SNDBUFSZ
+            BNE   :NOTEND                    ; See if it's the end
+            LDY   #0                         ; If so, wraparound
+:NOTEND     TYA
+            CMP   STARTINDICES,X             ; See if buffer is full
+            BEQ   :FULL
+            LDY   ENDINDICES,X               ; Current position
+            STA   ENDINDICES,X               ; Write updated input pointer
+            JSR   GETBUFADDR                 ; Buffer address into OSINTWS
+            PLA                              ; Get value back
+            STA   (OSINTWS),Y                ; Write to buffer
+            PLP                              ; Restore flags
+            CLC                              ; Exit with carry clear
+            RTS
+:FULL       PLA                              ; Restore A
+            PLP                              ; Restore flags
+            SEC                              ; Exit with carry set
+            RTS
+

auxmem.init.s

@@ -126,6 +126,14 @@ MOSHIGH     SEI                              ; Disable IRQ while initializing
             DEX
             BPL   :INITPG2
 
+            LDX   #3
+            LDA   #$80                       ; Initialize sound queues
+:INITSND    STA   SND0EMPTY,X
+            STZ   SND0STARTIDX,X
+            STZ   SND0ENDIDX,X
+            DEX
+            BNE   :INITSND
+
             LDA   $C036                      ; GS speed register
             AND   #$80                       ; Speed bit only
             STA   GSSPEED                    ; In Alt LC for IRQ/BRK hdlr

auxmem.mosequ.s

@@ -69,14 +69,17 @@ FSCV         EQU   $21E        ; FSCV misc file ops
 
 BYTEVARBASE  EQU   $190        ; Base of OSBYTE variables
 
+EMPTYFLAGS   EQU   $2CF
 SND0EMPTY    EQU   $2D3        ; Empty flag for sound bufs
 SND1EMPTY    EQU   $2D4
 SND2EMPTY    EQU   $2D5
 SND3EMPTY    EQU   $2D6
+STARTINDICES EQU   $2D8
 SND0STARTIDX EQU   $2DC        ; Start index for sound bufs
 SND1STARTIDX EQU   $2DD
 SND2STARTIDX EQU   $2DE
 SND3STARTIDX EQU   $2DF
+ENDINDICES   EQU   $2E1
 SND0ENDIDX   EQU   $2E5        ; End index for sound bufs
 SND1ENDIDX   EQU   $2E6
 SND2ENDIDX   EQU   $2E7