91C94 Ver la hoja de datos (PDF) - SMSC -> Microchip

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91C94

ISA/PCMCIA Single-Chip Ethernet Controller with RAM

SMSC -> Microchip 

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

TOO

BADCRC ODDFRM TOOLNG SHORT

LOW

BYTE

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:

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.

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