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In order to have randomize() work as expected (and the Apple II random number generation in general) it is necessary to update the random counter during keypress wait just like the ROM function does.
53 lines
1.3 KiB
ArmAsm
53 lines
1.3 KiB
ArmAsm
;
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; Kevin Ruland
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;
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; char cgetc (void);
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;
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; If open_apple key is pressed then the high-bit of the key is set.
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;
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.export _cgetc
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.import cursor, putchardirect
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.include "apple2.inc"
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_cgetc:
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; Cursor on ?
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lda cursor
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beq :+
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; Show caret.
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.ifdef __APPLE2ENH__
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lda #$7F | $80 ; Checkerboard, screen code
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.else
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lda #' ' | $40 ; Blank, flashing
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.endif
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jsr putchardirect ; Returns old character in X
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; Wait for keyboard strobe.
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: inc RNDL ; Increment random counter low
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bne :+
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inc RNDH ; Increment random counter high
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: lda KBD
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bpl :-- ; If < 128, no key pressed
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; Cursor on ?
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ldy cursor
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beq :+
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; Restore old character.
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pha
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txa
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jsr putchardirect
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pla
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; At this time, the high bit of the key pressed is set.
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: bit KBDSTRB ; Clear keyboard strobe
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.ifdef __APPLE2ENH__
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bit BUTN0 ; Check if OpenApple is down
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bmi done
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.endif
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and #$7F ; If not down, then clear high bit
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done: ldx #>$0000
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rts
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