From: Jim Brain (brain_at_jbrain.com)
Date: 2004-04-12 08:54:54
Well, interesting to me. I'm not a whiz at ML, and I found the following code It's from the QLink disk (yes, that disk...) I know it is a checksum, but I can;t figure out what math it is trying to do. The sequence 7f,7f,23,05,09 generates checksum with bcff=82,bd00=3e I was wondering if someone could help me with this. The end result will be in C, but I can do that myself if I can just figure out the algorithm. .C:bccf 8D FE BC STA $BCFE .C:bcd2 98 TYA .C:bcd3 48 PHA .C:bcd4 A2 08 LDX #$08 .C:bcd6 4E FE BC LSR $BCFE .C:bcd9 2A ROL A .C:bcda 29 01 AND #$01 .C:bcdc 4D 00 BD EOR $BD00 .C:bcdf 4E FF BC LSR $BCFF .C:bce2 6A ROR A .C:bce3 90 0E BCC $BCF3 .C:bce5 A8 TAY .C:bce6 AD FF BC LDA $BCFF .C:bce9 4D FC BC EOR $BCFC .C:bcec 8D FF BC STA $BCFF .C:bcef 98 TYA .C:bcf0 4D FD BC EOR $BCFD .C:bcf3 8D 00 BD STA $BD00 .C:bcf6 CA DEX .C:bcf7 D0 DD BNE $BCD6 .C:bcf9 68 PLA .C:bcfa A8 TAY .C:bcfb 60 RTS .C:bcfc A0 01 LDY #$01 .C:bcfe 00 BRK .C:bcff 00 BRK .C:bd00 00 BRK Message was sent through the cbm-hackers mailing list
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