Tape Recovery Case Study #2
Result
When we compare the three different signal flows we detect very poor signals in both the Recovered and Clean Data, those errors will follow us all the way to the ninth "block", when as we can see in the Final Data the structure has changed. This is because this block is where the BLEEP LOADER is supposed to be initialized and executed to read the BLEEPLOAD Signal Structure. In this case it was impossible to reconstruct or even rebuild the data, due the Recovered Data was too incomplete.
Even if the analyses of the signals indicates a similar signal flow, in depth when we compare the Clean Data with the Final Data the errors are to fatal.
Here we can see the sync is correct and the Data is correct.
Even if the loader is correct and there are no errors. The following Data Signal is where things go wrong.
Since we can't reach the BLEEPLOAD it's more or less impossible to decode the Data Signal.
However I managed to disassemble the BLEEPLOAD TRIGGER
*=$5600
LDY #$00
B5602 JSR $559D
STA $0073,Y
INY
CPY #$08
BNE B5602
LDY #$20
B560F LDA $5600,Y
EOR ($A8),Y
STA $5600,Y
INY
BNE B560F
SEI
LDA #$2F
STA $00
LDA #$D6
T5621 .byte $BF,$80,$D8,$74,$68,$94,$95,$0D,$74,$57,$F2
STY $0E,X
ADC $C0DC
AND $EB
ADC $F1,X
TAY
T5636 .byte $42,$06,$00,$D0,$E1,$97,$AC,$9C,$88,$F0
T5640 .byte $05,$D7,$0E,$CA,$39,$F0,$64,$18,$54
LSR $08F3
LSR $ED,X
AND $8CF0
SED
LDY $75,X
CPY $7DBB
T5657 .byte $14,$F0,$17,$55,$F9,$C4,$A5,$5F,$D1
T5660 .byte $21,$D8,$D4,$7D,$08,$FC,$1B
ADC $1352,Y
ORA $A1
LDA $A3
LDY #$02
CPY #$82
T5672 .byte $14,$80
TYA
ADC $85,X
NOP
CLI
AND $0155,X
LSR $E8,X
EOR ($A9),Y
RTI
T5681 .byte $CF,$B6,$E3,$49,$A5,$72,$F6,$56,$79,$D2,$9E,$F4,$F8,$19,$C3
T5690 .byte $76,$FE,$0F,$C7,$53,$14,$F7,$0C,$DB,$00,$A0,$28,$B3
AND $54,X
LDY #$D7
LSR $20,X
STA $FA3B,Y
INY
CPY #$CA
T56A9 .byte $2F,$F8,$A2,$F5,$5F,$02,$4C
T56B0 .byte $35,$AB,$A2,$12,$5F,$FD,$20,$CA,$AB,$5A,$AB,$A0,$CD,$DE,$80,$14
T56C0 .byte $5A,$5A,$C5,$AB,$6F,$2D,$A2,$1A,$5F,$D7,$BD,$C8,$AA,$66,$C4,$05
T56D0 .byte $37,$17,$C9,$20,$2F,$0B,$60,$78,$DF,$F3,$55,$A5,$42,$2A,$A3
BNE T56B8
LSR $01,X
STA $42
LSR $F2,X
STA $FCEB
LDA #$54
T56EC .byte $72,$EA,$03
JMP $AAF6
SEI
JSR $AAF3
BCC $5709
T56F8 .byte $5B,$8D,$A5,$BD,$66,$C3,$83,$A9
This is going a bit over my head but yeah, it was fun to be able to crack this nut in a way.