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40 lines
1.1 KiB
Plaintext
40 lines
1.1 KiB
Plaintext
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;-------------------------------
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; #JMPB4BB
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; boot2 jumps to $B4BB for a
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; nibble check
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; e.g. Troll's Tale
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;-------------------------------
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_jmpb4bb
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lda gIsMaster ; if DOS 3.3 lomem bootloader
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bne jmpb4bb_exit
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lda #$0C
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sta gDisplayBytes
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ldx #$84
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ldy #$03
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jsr compare ; and T00,S0C,$84 ==
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!byte $4C,$BB,$B4
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bcs jmpb4bb_exit
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lda #s_jmpb4bb
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lda #$0C
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ldx #$84
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ldy #$03
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jsr modify ; then set T00,S0C,$84 =
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!byte $AD,$E9,$37
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;
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; also check a variant that redirects the DOS input
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; vector through code that is only loaded by the
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; protection check we just bypassed
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;
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lda #$0D
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ldx #$BA
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ldy #$03
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jsr compare ; if T00,S0D,$BA ==
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!byte $4C,$0B,$37
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bcs jmpb4bb_exit
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lda #$0D
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ldx #$BA
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ldy #$03
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jsr modify ; then set T00,S0D,$BA =
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!byte $6C,$38,00
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jmpb4bb_exit
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