Non-PCI Single-Chip Full Duplex Ethernet Controller
RECEIVE FRAME STATUS WORD (in RAM)
This word is written at the beginning of each receive frame in memory. It is not available as a register.
ALGN
ERR
BROD CAST BADCRC ODDFRM
TOOLN TOO
G
SHO
RT
HASH VALUE
MULT
CAST
5
4
3
2
1
0
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 the 802.3 maximum size (1518 bytes on the cable).
TOOSHORT - The received frame is shorter than the 802.3 minimum size (64 bytes on the cable).
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 are shown in the table below:
ADDRESS
HASH VALUE 5-0
000 000
MULTICAST TABLE BIT
MT-0 bit 0
ED 00 00 00 00 00
0D 00 00 00 00 00
01 00 00 00 00 00
2F 00 00 00 00 00
010 000
MT-2 bit 0
100 111
111 111
MT-4 bit 7
MT-7 bit 7
MULTCAST - Receive frame was multicast. If hash value corresponds to a multicast table bit that is set,
and the address was a multicast, the packet will pass address filtering regardless of other filtering criteria.
Rev. 11/18/2004
Page 32
SMSC DS – LAN91C96I
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