mirror of
https://github.com/bobbimanners/Applecorn.git
synced 2024-06-30 01:29:43 +00:00
65 lines
2.1 KiB
ArmAsm
65 lines
2.1 KiB
ArmAsm
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* AUXMEM.AUDIO.S
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* (c) Bobbi 2022 GPLv3
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*
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* Applecorn audio code
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*
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SNDBUFSZ EQU 16 ; All audio buffers are 16 bytes
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* Get address of sound buffer
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* On entry: X is buffer number
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* On exit: OSIRQWS points to start of buffer
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* Called with interrupts disabled
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GETBUFADDR LDA :BUFADDRL,X
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STA OSINTWS+0
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LDA :BUFADDRH,X
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STA OSINTWS+1
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RTS
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:BUFADDRL DB $00
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DB $00
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DB $00
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DB $00
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DB <SNDBUF0
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DB <SNDBUF1
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DB <SNDBUF2
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DB <SNDBUF3
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DB $00
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:BUFADDRH DB $00
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DB $00
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DB $00
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DB $00
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DB >SNDBUF0
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DB >SNDBUF1
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DB >SNDBUF2
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DB >SNDBUF3
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DB $00
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* Insert value into buffer (INSV)
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* On entry: A is value, X is buffer number.
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* On exit: A, X preserved. C clear on success.
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INSHND PHP ; Save flags, turn off interrupts
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SEI
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PHA
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LDY ENDINDICES,X ; Get input pointer
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INY ; Next byte
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CPY #SNDBUFSZ
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BNE :NOTEND ; See if it's the end
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LDY #0 ; If so, wraparound
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:NOTEND TYA
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CMP STARTINDICES,X ; See if buffer is full
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BEQ :FULL
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LDY ENDINDICES,X ; Current position
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STA ENDINDICES,X ; Write updated input pointer
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JSR GETBUFADDR ; Buffer address into OSINTWS
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PLA ; Get value back
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STA (OSINTWS),Y ; Write to buffer
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PLP ; Restore flags
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CLC ; Exit with carry clear
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RTS
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:FULL PLA ; Restore A
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PLP ; Restore flags
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SEC ; Exit with carry set
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RTS
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