Echelon Neuron C - Manual (Page 97)

Neuron C Reference Guide 77
1 2 15 16 + + +
x x x
This function is useful in conjunction with the support for the Touch I/O model,
but can also be used whenever a CRC is needed.
Syntax
#include <stdlib.h>
unsigned long crc16 (unsigned long
crc , unsigned new_data );
Example
#include <stdlib.h>
unsigned data[SIZE];
void f(void)
{
unsigned i; // Or 'unsigned long' depending on SIZE
long crc;
crc = 0;
for (i = 0; i < SIZE; ++i) {
// Combine partial CRC with next data value
crc = crc16(crc, data[i]);
}
}
crc16_ccitt( ) Function
The crc16_ccitt( ) function iteratively calculates a 16-bit Comité Consultatif
International Téléphonique et Télégraphique
1 (CCITT) cyclic redundancy check
(CRC) over an array of data bytes using the following polynomial:
1
5 12 16 + + +
x x x
Apart from using a different polynomial, this function differs from the crc16( )
function in that this function operates on a data array, which is generally faster.
This function is useful in conjunction with the support for the Touch I/O model,
but can also be used whenever a CRC is needed.
Syntax
#include <stdlib.h>
extern system far unsigned long crc16_ccitt (unsigned long
crc_in ,
const unsigned *sp , unsigned len );
crc-in Specifies the input seed for the CRC calculation.
sp Specifies a pointer to the buffer that contains the data to
be checked.
1
International Telegraph and Telephone Consultative Committee.