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Routine $0725:   Counts the data bytes (returned in A,Y) until next SYNC
                 is detected. CF:=1.

This routine waits for the next SYNC mark and counts Y++ in the meanwhile
(count data bytes until next SYNC and return this value to calling routine
in A and Y). Is used e.g. to count the $7B's in the hidden sectors.


Jump from $072E:

0725: B8        CLV

JSR from $0490***, $0749, Jump from $072B:

0726: AD 00 1C  LDA $1C00      ; bit 7 of [$1C00] tells if SYNC is found
0729: 10 05     BPL $0730      ; branch to exit if SYNC found (bit 7 = 0)

072B: 50 F9     BVC $0726

072D: C8        INY            ; Y++ for each data byte
072E: 70 F5     BVS $0725

Jump from $0729:

0730: 98        TYA            ; return data byte count in A and Y
0731: 38        SEC            ; CF:=1
0732: 60        RTS

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