SMC91C100 Datasheet, PDF (19/83 Pages) List of Unclassifed Manufacturers – FEAST Fast Ethernet Controller

RECEIVE FRAME STATUS WORD
This word is written at the beginning of each receive frame in memory. It is not available as a register.
HIGH BYTE
ALGN ERR
BROD
CAST
BAD
CRC
ODD
FRM
TOOL
NG
TOO
SHORT
LOW BYTE
HASH VALUE
MULT
5
4
3
2
1
0 ^CAST
ALGNERR Frame had alignment error. When MII
SEL=1 alignment error is set when BADCRC=1 and
an odd number of nibbles were received between
SFD and RX_DV going inactive. When MII SEL=0
alignment error is set when BADCRC=1 and the
number of bits received between SFD and the CRS
going inactive is not an octet multiple.
BRODCAST Receive frame was broadcast.
BADCRC Frame had CRC error, or RX_ER was
asserted during reception.
ODDFRM This bit, when set, indicates that the
received frame had an odd number of bytes.
TOOLNG Frame length was longer than 802.3
maximum size (1518 bytes on the cable).
TOOSHORT Frame length was shorter than 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:
ADDRESS
ED 00 00 00 00 00
0D 00 00 00 00 00
01 00 00 00 00 00
2f 00 00 00 00 00
HASH VALUE 5-0
000 000
010 000
100 111
111 111
MULTICAST TABLE BIT
MT-0 bit 0
MT-2 bit 0
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.
19