Campbell Hausfeld SDM-SIO4 manual Transmitted Data, CRC32

SDM-SIO4 User Guide

1,2	CRC16 and CRC16-CCITT	0.159ms/char.
3	CRC16-CCITT-IBM	0.159ms/char.
4	CRC32	0.369ms/char.
5	CSI Signature	0.077ms/char.
6	Checksum using modulo 256	0.066ms/char.
7	Checksum using modulo 8192	0.071ms/char.

c

The time for the different data types is shown below. Note that this is the time needed to convert the received signature into a known format and is done at the end of the signature calculation before the compare. The ASCII decimal conversion timing is for a number with ten or more digits. If the number is less than this, the 1.125ms figure shown would reduce by 0.1ms per digit.

1	8 bit binary	0.155ms
2,3	16 bit binary	0.216ms
4,5	32 bit binary	0.334ms
6	ASCII decimal	1.125+(0.075*characters)ms
7	8 bit ASCII hex	0.226ms
8	16 bit ASCII hex	0.355ms
9	32 bit ASCII hex	0.613ms

d

When using CRC32 and CRC16-CITT there is a extra 0.19ms for an additional calculation. This is required as part of the CRC algorithm.

The total extra processing time over and above the SDM-SIO4’s normal delay is calculated by the following:

The extra time, in milliseconds, you must wait before trying to get the data from the SDM-SIO4 = a+(one from b)+(one from c)+(d if applicable)

6.3 Transmitted Data

The SDM-SIO4 can also do transmission signature generation with the calculated signature appended to the end of the string. This is done by the formatter types ‘g’ and ‘G’. Formatter type ‘g’ is used to mark where signature calculation should start and the type of signature/CRC to use. Formatter type ‘G’ is used to mark the end of signature generation, the position in the string where the calculated signature will be transmitted and the transmitted signature data format. The formatter types are described in detail below:

gn

This formatter type can be put into the formatter string to mark the start of a signature generation. When this happens the signature type determined by ‘n’ will be initialised ready to start signature calculation for all characters until formatter Gn is encountered. ‘n’ can be in the range of 0-255. The signature types supported are shown below:

0No Signature type used.

1CRC16 standard. Polynomial x16+x15+x2+1.

2CRC16-CCITT standard. Polynomial x16+x12+x5 +1.

3CRC16-CCITT-IBM (Tag Receiver).

4CRC32 standard.

Polynomial x32+x26+x23+x22+x16+x12+x11+x10+x8+x7+x5+x4+x2+x+1.

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