AD7176-2 datasheet(39/68 Pages) AD

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Data Sheet

AD7176-2

Rev. 0 | Page 39 of 68

CRC CALCULATION

Polynomial

The checksum, which is 8-bits wide, is generated using the polynomial

x8 + x2 + x + 1

To generate the checksum, the data is left shifted by eight bits to create a number ending in eight Logic 0s. The polynomial is aligned so that

its MSB is adjacent to the leftmost Logic 1 of the data. An XOR (exclusive OR) function is applied to the data to produce a new, shorter

number. The polynomial is again aligned so that its MSB is adjacent to the leftmost Logic 1 of the new result, and the procedure is repeated. This

process is repeated until the original data is reduced to a value less than the polynomial. This is the 8-bit checksum.

Example of a Polynomial CRC Calculation—24-Bit Word: 0x654321 (Eight Command Bits and 16-Bit Data)

An example of generating the 8-bit checksum using the polynomial based checksum is as follows:

Initial value

011001010100001100100001

01100101010000110010000100000000

left shifted eight bits

x8 + x2 + x + 1

100000111

polynomial

100100100000110010000100000000

XOR result

100000111

polynomial

100011000110010000100000000

XOR result

100000111

polynomial

11111110010000100000000

XOR result

100000111

polynomial value

1111101110000100000000

XOR result

100000111

polynomial value

111100000000100000000

XOR result

100000111

polynomial value

11100111000100000000

XOR result

100000111

polynomial value

1100100100100000000

XOR result

100000111

polynomial value

100101010100000000

XOR result

100000111

polynomial value

101101100000000

XOR result

100000111

polynomial value

1101011000000

XOR result

100000111

polynomial value

101010110000

XOR result

100000111

polynomial value

1010001000

XOR result

100000111

polynomial value

10000110

checksum = 0x86.

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