LAN91C100FD_08 datasheet(21/77 Pages) SMSC

21 / 77 page

FEAST Fast Ethernet Controller with Full Duplex Capability

SMSC LAN91C100FD Rev. D

Page 21

Revision 1.0 (09-22-08)

DATASHEET

ALGNERR - Frame had alignment error. When MII SEL=1 alignment error is set when BADCRC=1 and an

odd number of nibbles was 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

HASH VALUE 5-0

MULTICAST TABLE BIT

ED 00 00 00 00 00

0D 00 00 00 00 00

01 00 00 00 00 00

2F 00 00 00 00 00

000 000

010 000

100 111

111 111

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.

I/O SPACE

The base I/O space is determined by the IOS0-IOS2 inputs and the EEPROM contents. To limit the I/O

space requirements to 16 locations, the registers are assigned to different banks. The last word of the I/O

area is shared by all banks and can be used to change the bank in use. Registers are described using the

following convention:

OFFSET

NAME

TYPE

SYMBOL

HIGH

BYTE

bit 15

bit 14

bit 13

bit 12

bit 11

bit 10

bit 9

bit 8

LOW

BYTE

bit 7

bit 6

bit 5

bit 4

bit 3

bit 2

bit 1

bit 0

OFFSET - Defines the address offset within the IOBASE where the register can be accessed at, provided

the bank select has the appropriate value.

The offset specifies the address of the even byte (bits 0-7) or the address of the complete word.

The odd byte can be accessed using address (offset + 1).

Some registers (like the Interrupt Ack., or like Interrupt Mask) are functionally described as two eight bit

registers, in that case the offset of each one is independently specified.

Regardless of the functional description, all registers can be accessed as doublewords, words or bytes.

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