DaveR
Valued Contributor
Joined: 03 Sep 2005
Posts: 413
Location: Australia
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 Posted: Wed Oct 11, 2006 12:12 pm Post subject: CRC Lookup Tables |
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Anyone know how (or if it's possible) to convert the following Basic to VDS?
| Code: | CRC = 0
For Addr = StartAddr To EndAddr
CRC = CRCLookupTable(Data(Addr) Xor (CRC And 255)) Xor (CRC \ 256)
Next |
I'm trying calculate the value I need to change the 'Header CRC' to after changing the 'SystemID'.
| Code: | File Header 000000: 00 08 0E 98 01 96 00 01 00 06
1st 2 bytes = HeaderLength-2
2nd 2 bytes = Header CRC (SystemID+FileVersion+NrOfBlock)
3rd 2 bytes = SystemID
4th 2 bytes = FileVersion
5th 2 bytes = NrOfBlocks |
I assume I'd need to load this lookup table into a list?
| Code: | CRC16 ALGORITHM
The calculation is done via a 256 word lookup table.
0000 C0C1 C181 0140 C301 03C0 0280 C241
C601 06C0 0780 C741 0500 C5C1 C481 0440
CC01 0CC0 0D80 CD41 0F00 CFC1 CE81 0E40
0A00 CAC1 CB81 0B40 C901 09C0 0880 C841
D801 18C0 1980 D941 1B00 DBC1 DA81 1A40
1E00 DEC1 DF81 1F40 DD01 1DC0 1C80 DC41
1400 D4C1 D581 1540 D701 17C0 1680 D641
D201 12C0 1380 D341 1100 D1C1 D081 1040
F001 30C0 3180 F141 3300 F3C1 F281 3240
3600 F6C1 F781 3740 F501 35C0 3480 F441
3C00 FCC1 FD81 3D40 FF01 3FC0 3E80 FE41
FA01 3AC0 3B80 FB41 3900 F9C1 F881 3840
2800 E8C1 E981 2940 EB01 2BC0 2A80 EA41
EE01 2EC0 2F80 EF41 2D00 EDC1 EC81 2C40
E401 24C0 2580 E541 2700 E7C1 E681 2640
2200 E2C1 E381 2340 E101 21C0 2080 E041
A001 60C0 6180 A141 6300 A3C1 A281 6240
6600 A6C1 A781 6740 A501 65C0 6480 A441
6C00 ACC1 AD81 6D40 AF01 6FC0 6E80 AE41
AA01 6AC0 6B80 AB41 6900 A9C1 A881 6840
7800 B8C1 B981 7940 BB01 7BC0 7A80 BA41
BE01 7EC0 7F80 BF41 7D00 BDC1 BC81 7C40
B401 74C0 7580 B541 7700 B7C1 B681 7640
7200 B2C1 B381 7340 B101 71C0 7080 B041
5000 90C1 9181 5140 9301 53C0 5280 9241
9601 56C0 5780 9741 5500 95C1 9481 5440
9C01 5CC0 5D80 9D41 5F00 9FC1 9E81 5E40
5A00 9AC1 9B81 5B40 9901 59C0 5880 9841
8801 48C0 4980 8941 4B00 8BC1 8A81 4A40
4E00 8EC1 8F81 4F40 8D01 4DC0 4C80 8C41
4400 84C1 8581 4540 8701 47C0 4680 8641
8201 42C0 4380 8341 4100 81C1 8081 4040 |
_________________
cheers
Dave |
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