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CRC-CCITT


 

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Author Message
Pat
Guest







Jan 29, 2009 8:15 pm

This is the first time that I have looked at something of this nature. If my request is very basic then I apologise beforehand.

I have the following information where from the 2nd, 3rd, 4th and 5th pairs a cyclic redundancy check has been calculated using CRC-CCITT(16 bit) and the result stored at the 10th and 11th pairs. I understand the 7E is used to represent read only.

My question is how is the CRC calculated from the data.

7E 23 D2 3F 10 00 00 00 00 7C 45 7E 00 00
7E F6 DE 6D E0 00 00 00 00 94 F7 7E 00 00
7E 69 F9 DA 90 00 00 00 00 D4 D9 7E 00 00
7E B7 B9 EA 10 00 00 00 00 AC 9D 7E 00 00
73 73 A2 AC 10 00 00 00 00 33 04 7E 00 00
7E 90 C2 AC 10 00 00 00 00 38 52 7E 00 00
7E 8F F9 1B 10 00 00 00 00 FD 68 7E 00 00
7E 37 8A AC 10 00 00 00 00 37 E2 7E 00 00

Pat
Pat
Guest







Feb 01, 2009 2:29 pm

Sorted.

First of all the 2nd, 3rd, 4th and 5th pairs of data are converted to binary. Then the binary number is written back to front and converted back to hexadecimal. This can be done with the use of a Hackman calculator and the REV function.

The hexadecimal is then used in a CRC-CCITT calculator using Kermit parameters with an additional four pairs of 0.
Pat
Guest







Feb 01, 2009 2:41 pm

I omitted to mention that the CRC is also treated this way.
regregex
Preferred Member



Joined: 30 Oct 2007
Posts: 184
Location: London, UK

Feb 02, 2009 10:38 pm

It'll be quicker to use the XMODEM CRC:
"B7B9EA1000000000" (hex)
1 byte checksum 106
CRC-16 0x50B5
CRC-16 (Modbus) 0x5BF5
CRC-16 (Sick) 0x3B29
CRC-CCITT (XModem) 0xAC9D
CRC-CCITT (0xFFFF) 0x9DA3
CRC-CCITT (0x1D0F) 0x4DA4
CRC-CCITT (Kermit) 0x57B4
CRC-DNP 0xA455
CRC-32 0xDBC3A5C2

--Greg
Pat
Guest







Feb 04, 2009 1:01 am

Thank you for that. I must enjoy making things difficult for myself.
Guest








May 06, 2009 8:59 pm

if read with KC that's true.

RW would give CRC-CCITT (Kermit) 0x57B4
uttam
Guest







Nov 29, 2013 5:33 pm

hey pat can you solve it and please post it one example.......... i need it please help ........ not by calculator but manually giving example or KERMIT ALGO
hahaha
New User



Joined: 20 Feb 2015
Posts: 1


Feb 20, 2015 11:52 am

I must enjoy making things difficult for myself.???

____________
GuL

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