ranjit@hpcilzb.HP.COM (Ranjit Padmanabhan) (05/20/88)
I am in the process of writing a synchronous driver to implement
SDLC/HDLC, for an IBM-PC. One of the requirements is that the driver
provide a routine to calculate the frame checksum using the CCITT V.41
polynomial :
16 12 5
X + X + X + 1
I've heard of the existence of a lookup table algorithm for implementing
this calculation in software. Does anyone know the reference or of any
other easy way for me to do this. Even better, does anyone have a func-
tion written in C that would do this, and could I have a copy ?
Thanks a lot,
Ranjit
ranjit%hpdtc@hplabs.HP.COM -or- ...!hplabs!hpdtc!ranjitjbh@mibte.UUCP (James Harvey) (06/03/88)
In article <1710001@hpcilzb.HP.COM>, ranjit@hpcilzb.HP.COM (Ranjit Padmanabhan) writes: > > I am in the process of writing a synchronous driver to implement > SDLC/HDLC, for an IBM-PC. One of the requirements is that the driver > provide a routine to calculate the frame checksum using the CCITT V.41 > polynomial : > 16 12 5 > X + X + X + 1 > I've heard of the existence of a lookup table algorithm for implementing > this calculation in software. Does anyone know the reference or of any > other easy way for me to do this. Even better, does anyone have a func- > tion written in C that would do this, and could I have a copy ? > > ranjit%hpdtc@hplabs.HP.COM -or- ...!hplabs!hpdtc!ranjit I have a book on doing AX-25 packet radio in Z-80 software called "Synchronous Packet Radio Using the Software Approach" from Richcraft Engineering. In their packet program they use the lookup table method of generating CRC polynomials. The reference given for the method is an article by Aram Perez in the July 1983 'IEEE Micro Journal' titled 'Byte-wise CRC Calculations'. The Richcraft book does not discuss the root method in theoretical detail but describes the Machine Language routine which does the SDLC CRC in the packet program. It is only 27 bytes long. -- Jim Harvey | "Ask not for whom the bell Michigan Bell Telephone | tolls and you will only pay 29777 Telegraph | Station-to-Station rates." Southfield, Mich. 48034 | ihnp4!mibte!jbh or try ulysses!gamma!mibte!jbh