mirror of
https://github.com/Michaelangel007/apple2_mockingboard.git
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95 lines
971 B
Plaintext
95 lines
971 B
Plaintext
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;TABLE ACCESS ROUTINE
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;FOR SLOT 4
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*
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ORG $8000
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;ADDRESSES FOR FIRST 6522
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PTR EQU $08 ;DATA POINTER
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ORA EQU $C401 ;PORT A
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LATCH EQU $900B ;LATCH SUB-ROUTINE
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WRITE EQU $9016 ;WRITE SUB-ROUTINE
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RESET EQU $9021 ;RESET SUB-ROUTINE
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;ADDRESSES FOR SECOND 6522
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PRT2 EQU $0A ;DATA POINTER
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ORA2 EQU $C481 ;PORT A
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LATCH2 EQU $9037 ;LATCH SUB-ROUTINE
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WRITE2 EQU $9042 ;RESET SUB-ROUTINE
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RESET2 EQU $904D ;RESET SUB-ROUTINE
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*
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*ROUTINES FOR FIRST 6255
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*
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START JSR RESET ;RESET SOUND CHIP
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LDY #$00 ;USED TO IDENTIFY REGISTER
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LOOP STY ORA ;# OF SOUND CHIP
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JSR LATCH
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LDA (PTR),Y ;GET DATA FROM TABLE
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STA ORA
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JSR WRITE ;STORE IN REGISTER
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CPY #$0F ;END OF DATA?
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BEQ DONE ;YES, EXIT
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INY
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JMP LOOP ;NO, GET NEXT SET
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DONE RTS ;RETURN
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*
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*ROUTINES FOR SECOND 6522
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*
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START2 JSR RESET2 ;SAME INSTRUCTIONS AS
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LDY #$00 ;ABOVE
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LOOP2 STY ORA2
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JSR LATCH2
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LDA (PTR2),Y
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STA ORA2
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JSR WRITE2
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CPY #$0F
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BEQ DONE2
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INY
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JMP LOOP2
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DONE2 RTS
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