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apple2_fantavision_reloaded
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Cleanup Magic Number C

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Michaelangel007 2017-03-26 12:45:25 -07:00
parent 1f0f6ab221
commit 15ec2f2764
1 changed files with 7 additions and 5 deletions
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README.md
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@ -313,8 +313,10 @@ but I'll be nice guy and provide a fully documented disassembly:
; Disk Drive P5 PROM Usage ZP and IO
P5.Buff = $26 ; 16-bit pointer to dest
P5.SlotX16 = $2B ; i.e. $60 = Slot 6
P5.TrackHave = $40
P5.WantTrack = $41 ;
P5.Nibs = $3C ; counter for $56 nibbles
P5.SecWant = $3D ;
P5.SecTotal = $0800 ; T00S0 @ $00: total number of sectors to load
@ -577,26 +579,26 @@ On my //e it looks this:
C699:28 PLP ; Don't care about carry, restore stack
C69A:C5 3D CMP P5.SecWant ; A=SectorHave == SectorWant? (init $00 from $C654)
C69C:D0 BE BNE ^0 ;^ $C65C
C69E:A5 40 LDA TrackHave ; (read from prologue)
C69E:A5 40 LDA P5.TrackHave ; (read from prologue)
C6A0:C5 41 CMP TrackWant ;
C6A2:D0 B8 BNE ^0 ;^ $C65C !=
C6A4:B0 B7 BCS ^1 ;^ $C65D >=
C6A6:A0 56 ^10 LDY #$56 ; Decode $56 nibbles in 6&2
C6A8:84 3C ^11 STY $3C
C6A8:84 3C ^11 STY P5.Nibs
C6AA:BC 8C C0 ^12 LDY DRIVE_DATA,X
C6AD:10 FB BPL ^12 ;^ $C6AA
C6AF:59 D6 02 EOR $36C-$96,Y ; [$96] $36C:00, $36C-$96=$2D6
C6B2:A4 3C LDY $3C ; [$FF] $3D5:3F, $2D6+$FF=$3D5
C6B2:A4 3C LDY P5.Nibs ; [$FF] $3D5:3F, $2D6+$FF=$3D5
C6B4:88 DEY
C6B5:99 00 03 STA $0300,Y ; Buf1 = [$300 .. $35B]
C6B8:D0 EE BNE ^11 ;^ $C6A8
C6BA:84 3C ^13 STY $3C ; Y = #FF
C6BA:84 3C ^13 STY P5.Nibs ; Y = #FF
C6BC:BC 8C C0 ^14 LDY DRIVE_DATA,X
C6BF:10 FB BPl ^14 ;^ $C6BC
C6C1:59 D6 02 EOR $36C-$96,Y
C6C4:A4 3C LDY $3C
C6C4:A4 3C LDY P5.Nibs
C6C6:91 26 STA ($26),Y
C6C8:C8 INY
C6C9:D0 EF BNE ^13 ;^ $C6BA