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59 lines
1.3 KiB
ArmAsm
59 lines
1.3 KiB
ArmAsm
; Tiny HGr
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; 8-byte Apple II Hi-res intro
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; by Vince `deater` Weaver, vince@deater.net --- d e s i r e ---
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; drops into the middle of the CHRGET get next token routine
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; that the Applesoft interpreter copies to $B1 - $C8 on boot
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; Depends on $F3 being executed as a NOP
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; zero page locations
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; ROM calls
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HGR2 = $F3D8
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HPOSN = $F411
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XDRAW0 = $F65D
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BKGND0 = $F3F4 ; A is color, after A=$40/$60, Y=0
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; $E6 needs to be $20/$40
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; alternately can jump slightly further
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; and have $1B be $20/$40
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tiny_hgr:
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;chrget B1: E6 B8 inc txtptrl
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; B3: D0 02 bne chrgot
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; B5: E6 B9 inc txtptrh
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;chrgot B7: AD 00 08 lda $800 txtprtrl/txtptrh
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; BA: C9 3A cmp #$3A
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; BC: B0 0A bcs end
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; BE: C9 20 cmp #$20
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; C0: F0 EF beq chrget
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; C2: 38 sec
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; C3: E9 30 sbc #$30
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; C5: 38 sec
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; C6: E9 D0 sbc #$D0
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; C8: 60 rts
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; we drop this at B8
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tiny_loop:
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.byte $2c ; BIT ; skips the BKGND0 first time through
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; otherwise it rights garbage all over
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; first 8k of RAM due to HGR_PAGE
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; not being set
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nop ; $EA ; points to ROM $EA2C as base for random colors
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jsr BKGND0 ; clear screen to value in A
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; $20 $F3 $F4, depends on f3/f4 being nops
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; first time through the loop
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jsr HGR2 ; HGR2 -- init full-screen hi-res graphics
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; zero flag set
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; code already in RAM does a BEQ
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