AM79C90JC datasheet(49/62 Pages) AMD

49 / 62 page

AMD

Am79C90

;

0024 35 1D 86

XOR

AX,POLYL

0027 81 F2 04C1

XOR

DX,POLYH

;

002B 0B C3

SETH30:

AX,BX

;PUT CONTROL BIT IN CRC0

002D D1 CD

ROR

BP,1

;ROTATE ADDRESS WORD

002F FE C9

DEC

;DECREMENT BIT COUNTER

0031 75 E1

JNZ

SETH20

0033 FE CD

DEC

;DECREMENT WORD COUNTER

0035 75 D6

JNZ

SETH10

;

FORMATION OF CRC COMPLETE, AL CONTAINS THE REVERSED HASH

;

CODE

0037 B9 000A

MOV

CX,10

003A D0 E0

SETH40:

SAL

AL,1

;REVERSE THE ORDER OF BITS IN AL

003C D0 DC

RCR

AH,1

;AND PUT IT IN AH

003E E2 FA

LOOP

SETH40

;

AH NOW CONTAINS THE HASH CODE

;

0040 8A DC

MOV

BL,AH

;BL = HASH CODE, BH IS ALREADY ZERO

0042 B1 03

MOV

CL,3

;DIVIDE HASH CODE BY 8

0044 D2 EB

SHR

BL,CL

;TO GET TO THE CORRECT BYTE

0046 B0 01

MOV

AL,01H

;PRESET FILTER BIT

0048 80 E45 07

AND

AH,7H

;EXTRACT BIT COUNT

004B 8A CC

MOV

CL,AH

004D D2 E0

SHL

AL,CL

;SHIFT BIT TO CORRECT POSITION

004F 08 01

[Dl + BX],AL

;SET IN HASH FILTER

0051 5D

POP

0052 5A

POP

0053 59

POP

0054 5B

POP

0055 58

POP

0056 C3

RET

;

0057

SETHASH ENDP

;

0057

CSEG1

ENDS

;

END

Program example in BASIC to generate the hash filter, for multicast addressing, in the C-LANCE.

100

REM

110

REM PROGRAM TO GENERATE A HASH NUMBER GIVEN AN ETHERNET ADDRESS

120

REM

130

DEFINT A–Z

140

DIM A(47): REM ETHERNET ADDRESS. 48 BITS.

150

DIM A$(6): REM INPUT FROM KEYBOARD

160

DIM C(32): REM CRC REGISTER–32 BITS

AM79C90JC Datasheet(PDF) 49 Page - Advanced Micro Devices

AM79C90JC Datasheet(HTML) 49 Page - Advanced Micro Devices

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