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Apple II Magazines (PO)
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Nibble Volume 10, No. 11 (1989-11)(MindCraft Publishing)(Side A).zip
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Nibble Volume 10, No. 11 (1989-11)(MindCraft Publishing)(Side A).po
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APPLE.ORGAN.txt
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Text File
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1996-12-24
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781b
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27 lines
ORG $300 ;PAGE 3 USER SPACE
PITCH EQU $7 ;TONE PITCH
KEYBD EQU $C000 ;KEYBOARD LOCATION
STROBE EQU $C010 ;KEYBOARD CLEAR STROBE
SPEAKER EQU $C030 :APPLE SPEAKER ADDRESS
WAIT EQU $FCA8 ;MON WAIT ROUTINE
LDA #$10 ;INITIALIZE THE PITCH
STA PITCH
KEYPRESS LDA KEYBD ;GET CURRENT KEY PRESS
BPL TONE ;NONE PRESSED YET
CMP #$9B ;ESC TO QUIT?
BEQ QUIT ; YES, GO QUIT
CMP #$C1 ;KEY VALUE TO LOW?
BCC TONE ;YES, SO GO GET ANOTHER
CMP #$DB ;KEY ASCII > "["?
BCS TONE ;YES, GO GET ANOTHER KEY
SEC ;PREPARE FOR SUBTRACTION
LDA #$DB ; MAKE "Z"=1, "Y"=2, ETC
SBC KEYBD ;SUBTRACT KEYBOARD VALUE
STA PITCH ;SAVE AS NEW PITCH
TONE LDA SPEAKER ;CLICK THE SPEAKER
LDA PITCH ;GET THE PITCH VALUE
JSR WAIT ;PAUSE A BIT
JMP KEYPRESS ;GO GET NEXT KEY
QUIT LDA STROBE ;CLEAR KEYBOARD
RTS