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Indent Stage 2
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Michaelangel007
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README.md
150
README.md
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@ -1155,91 +1155,91 @@ TODO: FIXME: Convert ProDOS Block # to Sector # ?
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Once the entire track $15 of Stage 2 is read in it is executed to read Stage 3.
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```asm
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TestBoot3: ; Boot Stage 2 done, do stage 3
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0873:A6 2B LDX P5.SlotX16 ;
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0875:86 FD STX RWTS_SLOTx16 ;
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0877:A9 BC LDA #>LoadBoot3 ; Load T$22 4&4 "4 sectors" @ $BC00, $BD00, $BE00, $BF00
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0879:20 00 B5 JSR ReadBoot3 ; Boot Stage 2 reads in encrypted Stage 3
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087C:B0 F5 BCS TestBoot3 ;^ $0873 C=1 error, Hang if NibbleCheck1 fails
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087E:4C 00 BE JMP ExecBoot3 ;
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TestBoot3: ; Boot Stage 2 done, do stage 3
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0873:A6 2B LDX P5.SlotX16 ;
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0875:86 FD STX rwts_SlotX16 ;
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0877:A9 BC LDA #>LoadBoot3 ; Load T$22 4&4 "4 sectors" @ $BC00, $BD00, $BE00, $BF00
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0879:20 00 B5 JSR ReadBoot3 ; Boot Stage 2 reads in encrypted Stage 3
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087C:B0 F5 BCS TestBoot3 ;^ $0873 C=1 error, Hang if NibbleCheck1 fails
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087E:4C 00 BE JMP ExecBoot3 ;
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```
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Let's disassemble $B500 ...
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```asm
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COUNT = $3E ; 16-bit counter
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DRIVE_DATA = $C08C ; Read Disk Nibble
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COUNT = $3E ; 16-bit counter
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DRIVE_DATA = $C08C ; Read Disk Nibble
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ReadBoot3:
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B500:8D 17 B5 STA _B516+1 ; *** SELF-MODIFYING *** DestAddr
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; These 3 bytes are wasted
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; Should just be STA $3D
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; And we can delete $B516..$B518
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B503:A9 22 LDA #$22 ; TRACK_NIBBLE_CHECK
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B505:20 09 B0 JSR RWTS_Seek ;
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B508:A6 FD LDX RWTS_SLOTx16 ;
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B50A:A9 80 LDA #$80 ; Attempt to read $8080 disk nibbles
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B50C:85 3E STA Count ; Count
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B50E:85 3F STA Count+1 ;
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B510:A9 04 LDA #$04 ; Num "Sectors" or Pages to read
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B512:85 3B STA NumSectors ;
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B514:A0 00 LDY #$00 ; Num disk nibbles read (actually is 1/2)
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_B516:
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B516:A9 00 LDA #$00 ; *** SELF-MODIFIED @ $B500 *** Dest Addr to Load at
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B518:84 3C STY $3C ;
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B51A:85 3D STA DestPage ; DestPage
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ReadBoot3:
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B500:8D 17 B5 STA _B516+1 ; *** SELF-MODIFYING *** DestAddr
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; These 3 bytes are wasted
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; Should just be STA $3D
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; And we can delete $B516..$B518
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B503:A9 22 LDA #$22 ; TRACK_NIBBLE_CHECK
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B505:20 09 B0 JSR RWTS_Seek ;
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B508:A6 FD LDX rwts_SlotX16 ;
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B50A:A9 80 LDA #$80 ; Attempt to read $8080 disk nibbles
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B50C:85 3E STA Count ; Count
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B50E:85 3F STA Count+1 ;
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B510:A9 04 LDA #$04 ; Num "Sectors" or Pages to read
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B512:85 3B STA NumSectors ;
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B514:A0 00 LDY #$00 ; Num disk nibbles read (actually is 1/2)
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_B516:
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B516:A9 00 LDA #$00 ; *** SELF-MODIFIED @ $B500 *** Dest Addr to Load at
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B518:84 3C STY $3C ;
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B51A:85 3D STA DestPage ; DestPage
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NextCount:
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B51C:C6 3E DEC Count ; Force read counter
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B51E:D0 06 BNE DoNibbleCheck1 ; to read at least once
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B520:C6 3F DEC Count+1 ;
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B522:D0 02 BNE DoNibbleCheck1 ;
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B524:38 SEC ; FAIL nibble check 1
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B525:60 RTS ;
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NextCount:
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B51C:C6 3E DEC Count ; Force read counter
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B51E:D0 06 BNE DoNibbleCheck1 ; to read at least once
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B520:C6 3F DEC Count+1 ;
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B522:D0 02 BNE DoNibbleCheck1 ;
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B524:38 SEC ; FAIL nibble check 1
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B525:60 RTS ;
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DoNibbleCheck1:
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WaitNib1a: ; ^
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B526:BD 8C C0 LDA DRIVE_DATA,X ; |
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B529:10 FB BPl WaitNib1a ;^ $B526 |
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TestNib1a: ; |
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B52B:C9 F5 CMP #$F5 ; $F5 | <--+
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B52D:D0 ED BNE NextCount ;^ $B51C + |
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; |
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WaitNib1b: ; |
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B52F:BD 8C C0 LDA DRIVE_DATA,X ; |
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B532:10 FB BPL WaitNib1b ;^ $B52F |
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TestNib1b: ; |
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B534:C9 F4 CMP #$F4 ; $F4 |
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B536:D0 F3 BNE TestNib1a ;^ $B52B ---+
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DoNibbleCheck1:
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WaitNib1a: ; ^
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B526:BD 8C C0 LDA DRIVE_DATA,X ; |
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B529:10 FB BPl WaitNib1a ;^ $B526 |
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TestNib1a: ; |
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B52B:C9 F5 CMP #$F5 ; $F5 | <--+
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B52D:D0 ED BNE NextCount ;^ $B51C + |
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; |
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WaitNib1b: ; |
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B52F:BD 8C C0 LDA DRIVE_DATA,X ; |
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B532:10 FB BPL WaitNib1b ;^ $B52F |
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TestNib1b: ; |
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B534:C9 F4 CMP #$F4 ; $F4 |
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B536:D0 F3 BNE TestNib1a ;^ $B52B ---+
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WaitNib1c:
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B538:BD 8C C0 LDA DRIVE_DATA,X;
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B53B:10 FB BPL WaitNib2b ;^ $B538
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TestNib1c:
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B53D:C9 CF CMP #$CF ; $CF
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B53F:D0 F3 BNE $B534
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WaitNib1c:
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B538:BD 8C C0 LDA DRIVE_DATA,X;
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B53B:10 FB BPL WaitNib2b ;^ $B538
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TestNib1c:
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B53D:C9 CF CMP #$CF ; $CF
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B53F:D0 F3 BNE $B534
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:
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B541:BD 8C C0 LDA $C08C,X ;+
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B544:10 FB BPL $B541 ;^
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B546:2A ROL
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B547:85 3A STA $3A
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B549:BD 8C C0 LDA $C08C,X ;+
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B54C:10 FB BPL $B549 ;^
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B54E:25 3A AND $3A
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B550:91 3C STA ($3C),Y
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B552:C8 INY
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B553:D0 EC BNE $B541
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B555:0E FF FF ASL $FFFF ; //e = $C3, //c = $C8, Laser128 = ? TODO: FIXME:
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B558:BD 8C C0 LDA $C08C,X
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B55B:10 FB BPL $B558 ;^
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B55D:C9 D5 CMP #$D5 ; $ D5
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B55F:D0 AF BNE $B510 ;^
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B561:E6 3D INC $3D ; Inc Dest Page
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B563:C6 3B DEC NumSectors ;
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B565:D0 DA BNE $B541 ;^
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B567:18 CLC ; PASS nibble check 1
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B568:60 RTS
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:
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B541:BD 8C C0 LDA $C08C,X ;+
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B544:10 FB BPL $B541 ;^
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B546:2A ROL
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B547:85 3A STA $3A
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B549:BD 8C C0 LDA $C08C,X ;+
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B54C:10 FB BPL $B549 ;^
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B54E:25 3A AND $3A
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B550:91 3C STA ($3C),Y
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B552:C8 INY
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B553:D0 EC BNE $B541
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B555:0E FF FF ASL $FFFF ; //e = $C3, //c = $C8, Laser128 = ? TODO: FIXME:
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B558:BD 8C C0 LDA $C08C,X
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B55B:10 FB BPL $B558 ;^
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B55D:C9 D5 CMP #$D5 ; $ D5
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B55F:D0 AF BNE $B510 ;^
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B561:E6 3D INC $3D ; Inc Dest Page
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B563:C6 3B DEC NumSectors ;
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B565:D0 DA BNE $B541 ;^
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B567:18 CLC ; PASS nibble check 1
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B568:60 RTS
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```
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This first nibble check reads these disk nibbles on Track $22:
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