lindahl@waltz.UUCP (01/02/85)
>I am looking for a routine, written in C, that can calculate and/or >generate the CRC field of the ethernet packet. I need this to >verify that the hardware is doing it correctly in a >diagnostic. All the mathematical definitions look like >'greek' to me and I would rather not have to figure it out. > >Thanx in advance. >Monte Pickard Counterpoint Computers ..!ucbvax!hplabs!oblio!monte /* ---------- */ Since I don't have my XEROX ETHERNET book handy, I don't remember if ETHERNET uses a 16-bit CRC. If it does, however, I can point you to an entry in NET.SOURCES which includes a C program. I have included a portion of the header so you can locate it there. Hope it helps ... (I'll double check the ETHERNET spec when I get it unpacked -- I moved recently). ============================================================================== The following are translations of byte-wise CRC-16 calculation algorithms given the the June 83 issue of IEEE Micro. Included are an on-the-fly 8086 assembler version, a C table driven version and a C program to produce the table as well as the table itself. I have tested these against each other and am fairly certain they work. If they don't, I apologize now -- please send me your fixes. ;=================================================================== ; ; CRC -- calculates CRC checksum on string of bytes ; on the stack -- length of string, string offset ; returns -- 16 bit CRC-16 value in AX, BX. ; other data regs. garbled NOTE IF CI CHANGES C COMPILER ; ; Programmer: Bryan Bingham 8 Nov 1983 ; System: CompuPro 8086/8085 ; ; This code is intended to be called by a C program compiled with the CI-86 ; compiler, the format of the directives is suggested by CI cvtobj document. ; It has no seperate data segment, it uses just registers. The algorithm ; comes from "Byte-wise CRC Calculations" by Aram Perez, IEEE Micro June ; 1983 pp.40-50 and uses several tricks based on the 8080/8086 design. ; I suggest getting that paper if you want to understand what is happening ; because I did not try to fully document the thing here, and the comments ; here only make sense after you read the paper. ; ; Called from C as crc(buf, strlen(buf)); ;=================================================================== ------------------------------------------------------------------------
darrelj@sdcrdcf.UUCP (Darrel VanBuer) (01/06/85)
Ethernet II uses a 32 bit CRC (the experimental 3 MB Ethernet uses a 16 bit
CRC)
--
Darrel J. Van Buer, PhD
System Development Corp.
2500 Colorado Ave
Santa Monica, CA 90406
(213)820-4111 x5449
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VANBUER@USC-ECL.ARPA