Calculate crc and/or checksums, many different algorithms and data formats.
Checksums Simple datacheck
CRC Advanced datacheck
modulus Number check, usual used for manuel entry and barcode number check

Algorithm

CRC 8	CRC with 8 bit polynomial, a useable polynomial is $07, see CRC calculations for coding examples
CRC 16	CRC with 16 bit polynomial, see CRC calculations for coding examples
CRC 16 std	Use the $8005 polynomial, see CRC calculations for coding examples
CRC 16 CCITT	Use the $1021 polynomial, see CRC calculations for coding examples
CRC 32	CRC with 32 bit polynomial, see CRC calculations for coding examples
CRC 32 std.	Use the $04C11DB7 polynomial, see CRC calculations for coding examples
CRC 32 I.363	Same as above, but other settings, see CRC calculations for coding examples
Checksum	Add all bytes
Checksum with zero result	Add all bytes and negate the result
Xor	Xor all bytes
16 bit checksum	Add all bytes in a 16 bit register
Modulus	Modulus check, used for numerical strings
Modulus 10 arithmetic	Mod 10 with 21 weights
Modulus 10 geometric	Mod 10 with 731 weights
Modulus 10 MSI	Mod 10 with 21 weights and "SumDigits"
Modulus 10 UPC/EAN	Mod 10 with 13 weights
Modulus 11 arithmetic	Mod 11 with 234567 weights
Modulus 11 geometric	Mod 11 with 2,4,8,5,10,9,7,3,6,1 weights
Modulus 11 danish CPR	Mod 11 with 765432 weights
Guess with checksum	Try to guess a checksum algorithm from a known checksum.
Guess	Try to guess what checksum algorithm was used on the data. It is assumed that the last databyte(s) contains the checksum.
Data view	List all the data in hex format, used to verify that the input is correctly read

Data format

It is very important to select the correct dataformat!

Hex/Text	A mix of numbers and text strings. Any number is supposed to be in hex and text must have quotes around it
Expression	Same syntax as in Calculator, expression can be delimetered with ;
Hex dump	Will decode typical hex dumps formats. I.e.: "address data text", the address and data fields are required, the text field is optional
Text	Any text, leading and trailing spaces and newlines are ignored
Text and spaces	Any text, only newlines are ignored

Parameters

Initial	Initial value for calculations
Alt	Another way to express the same initial value, the releation between "Initial" and "Alt" will depend on the agorithm
Final Xor	Invert some or all of the result bits
Polynom	The CRC polynomial, X^(n-1) first and X^0 last, X^n is assumed to be 1
Inverted	The CRC polynomial, X^0 first and x^(n-1) last, x^n is assumed to be 1
Reverse data	Reverse (reflect) data bits before procession
Reverse result	Reverse (reflect) result bits after procession, usual used together with "Reverse data"
Modulus	Modulus usual 10 or 11, but other values can be used. For digits above 9 use letters (A=10, B=11 etc.)
Weights	Values to multiply the digits with. The weights are specied as a list of numbers
Reminder	Reminder to display, usual calculated as "modulus-reminder" The reminders are specied as a list of numbers, one for each reminder value
Apply weight from left	Select between applying weight from left or right
Sum digits	In modulus the sum is calculated from the weights. I.e. a 9 digit with a 3 weight adds 9*3=27 to the weight, but when this parameter is checked it will give 2+7=9 to the weight
Edit params	Press this buttoms to copy the parameters to the generic algorithm

Output

The first part of the output is just a list of the parameters used.
Some values are also listet as ascii values, this is a combination of characters, character names and hex values
When doing modulus checks, two calculations are done:
1) A modulus digit is calculated for the number
2) The number is assumed to contain a modulus digit and a check is performed

To get a pregenerated crc table, select the data format with the "Save format" checkbox and press "Save".
CaveatDo not specify an inverted polynom, when "Reverse data" are checkmarked the necessary bit manipulation are done automatic.

Hints

When using crc the polynom is very important for the quality of the data check (i.e. do not make your own polynom, but use a verified one).
To check a small (<64K) file use "DataFormat=Expression" and "Data=FileLoad("filename")"
CRC often uses reverse data to simulate the bitstream of a serial line with lsb first
A CRC must have a non-zero initial value to protect leading $00 bytes
CRC algorithms exist in two flavors: normal and inverted. They give the same result when handled correctly
The CRC function in the Calculator is using the reversed algorithm, this also means that it is working with reverse data
Different types of MSI modulus check exists.
See CRC calculations for coding examples

Calculator functions

The Calculator also support some crc calculations:


CRC8(poly,initial,string)

CRC16(poly,initial,string)

CRC32(poly,initial,string)

CRCPoly(coefficients)

CRCPolyReverse(ReversePolyValue)

Other pages

MPU Support list where MiscEl can help when working with microprocessors

MiscEl: CRC and checksum