LAN91C111_11 Datasheet, PDF (45/133 Pages) SMSC Corporation – 10/100 Non-PCI Ethernet Single Chip MAC + PHY

10/100 Non-PCI Ethernet Single Chip MAC + PHY
Datasheet
8.2 Receive Frame Status
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
TOOLNG
TOO
SHORT
LOW
BYTE
HASH VALUE
MULT
CAST
Reserved
5
4
3
2
1
0
ALGNERR - Frame had alignment error.
BROADCAST - Receive frame was broadcast. When a broadcast packet is received, the MULTCAST
bit may be also set on the status word in addition to the BRODCAST bit. The software implement may
just ignore the MULTCAST bit if for BRODCAST packet.
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.
SMSC LAN91C111 REV C
45
DATASHEET
Revision 1.92 (06-27-11)