crc16_checksum.h File Reference

Detailed Description

Inline CRC16 Checksum insertion and verification.

This file defines two commonly-used formats for "CCITT" CRC16 checksums. Both are commonly used variants of the "CRC16-CCITT" standard defined in ITU-T Recommendation V.41. "KERMIT" is the LSB-first variant and "XMODEM" is the MSB-first variant.

For more information, see discussion from Greg Cook: https://reveng.sourceforge.io/crc-catalogue/16.htm#crc.cat.crc-16-ibm-3740 https://reveng.sourceforge.io/crc-catalogue/16.htm#crc.cat.crc-16-kermit https://reveng.sourceforge.io/crc-catalogue/16.htm#crc.cat.crc-16-xmodem

The blocks below transmit or receive sequences where the the CRC16 appears at the end of the encoded frame. The KermitTx and XmodemTx classes accept the frame contents and append the designated CRC16 variant. The KermitRx and XmodemRx classes verify the checksum of incoming frames, calling write_finalize() or write_abort() appropriately.

Note that the CRC16 used in the CCSDS "AOS Space Data Link Protocol" (Blue Book 732.0-B-4) is equivalent to "IBM-3740" (link above), which is the "XMODEM" variant with an initial value of 0xFFFF instead of zero.

Definition in file crc16_checksum.h.

#include <satcat5/io_checksum.h>

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Classes
class	satcat5::crc16::KermitTx
	Append FCS to each outgoing frame ("KERMIT" variant). More...
class	satcat5::crc16::KermitRx
	Check and remove FCS from each incoming frame ("KERMIT" variant). More...
class	satcat5::crc16::XmodemTx
	Append FCS to each outgoing frame ("XMODEM" variant). More...
class	satcat5::crc16::XmodemRx
	Check and remove FCS from each incoming frame ("XMODEM" variant). More...

Functions
u16	satcat5::crc16::kermit (unsigned nbytes, const void *data)
	Directly calculate CRC16 on a block of data. More...
u16	satcat5::crc16::xmodem (unsigned nbytes, const void *data)
	Directly calculate CRC16 on a block of data. More...

Function Documentation

kermit()

u16 satcat5::crc16::kermit	(	unsigned	nbytes,
		const void *	data
	)

Directly calculate CRC16 on a block of data.

This is the "KERMIT" variant,

See also

crc16_checksum.h.

Definition at line 151 of file crc16_checksum.cc.

xmodem()

u16 satcat5::crc16::xmodem	(	unsigned	nbytes,
		const void *	data
	)

Directly calculate CRC16 on a block of data.

This is the "XMODEM" variant,

See also

crc16_checksum.h.

Definition at line 160 of file crc16_checksum.cc.