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35 lines
2.1 KiB
Plaintext
35 lines
2.1 KiB
Plaintext
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0000- 4
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0000- 5 * ----------------------------------------------------------------------
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0000- 6 * SAMPLE PROGRAM AS FOUND IN THE BOOK "6502 APPLICATIONS BOOK" BY RODNEY
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0000- 7 * ZAKS, IT IS A SOFTWARE METHOD OF CONTROLLING SOUND DURATION.ADAPTED FOR
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0000- 8 * THE KIM-1 WITH THE 6502 PROJECT PLATFORM BOARD / COVOX PROJECT BOARD.
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0000- 9 *
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0004- 10 DELAY .EQ $04
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0000- 11
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1700- 12 VIA .EQ $1700
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1700- 13 IRB .EQ VIA
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1701- 14 ORA .EQ VIA+1
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1702- 15 DDRB .EQ VIA+2
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1703- 16 DDRA .EQ VIA+3
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0000- 17
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0200- 18 .OR $0200
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0200- 19 .TA $0200
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0200-A9 80 20 ( 2) START LDA #$80 LOAD A DEFAULT VALUE, START PROGRAM AT
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0202-85 04 21 ( 2) STA DELAY BSCSPK TO JUST USE ZP $04 AS IN THE BOOK.
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0204-A9 FF 22 ( 2) BSCSPK LDA #$FF SET PORT A
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0206-8D 03 17 23 ( 4) STA DDRA AS OUTPUTS
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0209- 24
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0209-A9 20 25 ( 2) AGAIN LDA #$20 DEFAULT VOLUME
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020B-8D 01 17 26 ( 4) STA ORA SET SPEAKER DRIVER HIGH
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020E-20 1C 02 27 ( 6) JSR DLYB CALL DELAY
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0211-A9 00 28 ( 2) LDA #$00
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0213-8D 01 17 29 ( 4) STA ORA SET SPEAKER DRIVER LOW
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0216-20 1C 02 30 ( 6) JSR DLYB CALL DELAY
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0219-4C 09 02 31 ( 3) JMP AGAIN
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021C- 32
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021C-A6 04 33 ( 3) DLYB LDX DELAY LOAD DELAY VALUE INTO X
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021E-E8 34 ( 2) LPXB INX INCREMENT X
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021F-E0 00 35 ( 2) CPX #$00
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0221-30 FB 36 (2**) BMI LPXB LOOP TILL (X)=0
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0223-60 37 ( 6) RTS
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