lan91c95 Standard Microsystems Corp., lan91c95 Datasheet - Page 31

• Manufacturer Part Number: lan91c95
• Description: Isa/pcmcia Full Duplex Single-chip Ethernet And Modem Controller With Ram
• Manufacturer: Standard Microsystems Corp.

RECEIVE FRAME STATUS WORD
This word is written at the beginning of each receive frame in memory. It is not available as a register.
ALGNERR - Frame had alignment error.
BRODCAST - Receive frame was broadcast.
BADCRC - Frame had CRC error.
ODDFRM - This bit when set indicates that the
received frame had an odd number of bytes.
TOOLNG - The received frame is longer than
802.3 maximum size (1518 bytes on the cable).
TOOSHORT - The received frame is shorter than
802.3 minimum size (64 bytes on the cable).
MULTCAST - Receive frame was multicast. If hash
value corresponds to a multicast table bit that is
set, and the address was a multicast, the
BYTE
BYTE
HIGH
LOW
ALGN
ED 00 00 00 00 00
0D 00 00 00 00 00
ERR
01 00 00 00 00 00
2F 00 00 00 00 00
ADDRESS
BROD
CAST
5
CRC
BAD
4
HASH VALUE 5-0
000 000
010 000
100 111
111 111
ODD
FRM
HASH VALUE
3
31
HASH VALUE - Provides the hash value used to
index the Multicast Registers. Can be used by
receive routines to speed up the group address
search. The hash value consists of the six most
significant bits of the CRC calculated on the
Destination Address, and maps into the 64 bit
multicast table. Bits 5,4,3 of the hash value select a
byte of the multicast table, while bits 2,1,0
determine the bit within the byte selected.
Examples of the address mapping:
packet will pass address filtering regardless of
other filtering criteria.
TOOLNG
2
MULTICAST TABLE BIT
SHORT
TOO
1
MT-0 bit 0
MT-2 bit 0
MT-4 bit 7
MT-7 bit 7
0
MULT
CAST