33 lines
960 B
NASM
33 lines
960 B
NASM
.CR 6502
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.TF siren.hex,INT
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.LF siren.list
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* ----------------------------------------------------------------------
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* SIREN PROGRAM AS FOUND IN THE BOOK "6502 APPLICATIONS BOOK" BY RODNEY
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* ZAKS. ADAPTED FOR THE KIM-1 WITH THE 6502 PROJECT PLATFORM BOARD AND
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* COVOX PROJECT BOARD.
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*
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DELAY .EQ $D1
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VIA .EQ $1700
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IRB .EQ VIA
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ORA .EQ VIA + $1
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DDRB .EQ VIA + $2
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DDRA .EQ VIA + $3
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.OR $0200
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.TA $0200
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START LDA #$FF SET PORT A
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STA DDRA AS OUTPUTS
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STA DELAY INITIALIZE DELAY
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LDA #$03 INITIALIZE VOLUME
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STA ORA
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SWITCH LDA #$FF EXCLUSIVE OR WITH
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EOR ORA MASK $FF IS USED
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STA ORA TO INVERT OUTPUT.
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LDX DELAY
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LOOP DEX
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BNE LOOP
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DEC DELAY
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JMP SWITCH |