AM79C90 Advanced Micro Devices, AM79C90 Datasheet - Page 51

• Manufacturer Part Number: AM79C90
• Description: CMOS Local Area Network Controller for Ethernet (C-LANCE)
• Manufacturer: Advanced Micro Devices

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Program example in C to generate the hash filter, for multicast addressing in the C-LANCE.
/************************************************************
* hash.c
* Generate a logical address filter value from a list of
* Ethernet multicast addresses.
*
* Input:
*
*
*
*
*
*
*
*
*
*
*
* Output:
*
*
*
*
****************************************************************/
#include <stdio.h>
void updateCRC (int bit);
void main()
int adr[6],
User is prompted to enter an Ethernet address in
Ethernet hex format: First octet entered is the first
After results are printed, user is prompted for
another address.
(Note that the first octet transmitted is stored in
the C-LANCE as the least significant byte of the Physical
Address Register.)
After each address is entered, the program prints the
hash code for the last address and the cumulative
address filter function. The filter function is
printed as 8 hex bytes, least significant byte first.
ladrf[8], /* Logical address filter */
CRC[33],
poly[] =
};
C(1) = C(1) XOR 1: C(2) = C(2) XOR 1: C(4) = C(4) XOR 1
C(5) = C(5) XOR 1: C(7) = C(7) XOR 1: C(8) = C(8) XOR 1
C(10) = C(10) XOR 1: C(11) = C(11) XOR 1: C(12) = C(12) XOR 1
C(16) = C(16) XOR 1: C(22) = C(22) XOR 1: C(23) = C(23) XOR 1
C(26) = C(26) XOR 1
C(0) = 1
NEXT N
REM
REM CRC COMPUTATION COMPLETE, EXTRACT HASH NUMBER FROM C(0) TO C(5)
REM
HH=32*C(0)+16*C(1)+8*C(2)+4*C(3)+2*C(4)+C(5)
PRINT “THE HASH NUMBER FOR ”;
PRINT A$(0); “ ”; A$(1); “ ”; A$(2); “ ”; A$(3); “ ”; A$(4); “ ”; A$(5);
PRINT “IS”; HH
GOTO 210
{1,1,1,0, 1,1,0,1,
1,0,1,1, 1,0,0,0,
1,0,0,0, 0,0,1,1,
0,0,1,0, 0,0,0,0
octet to appear on the line. LSB of most
significant octet is the first bit on the line.
Octets are separated by blanks.
Rev 0.1
the x**n term of the CRC generator polynomial. */
/* CRC polynomial. poly[n] = coefficient of
/* Ethernet address */
/* CRC register, 1 word/bit + extra control bit */
Am79C90
AMD
51