91C100FDREVB Datasheet, PDF (18/68 Pages) SMSC Corporation – FEAST FAST ETHERNET CONTROLLER WITH FULL DUPLEX CAPABILITY

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.
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
bit 15
bit 14
bit 13
bit 12
bit 11
bit 10
bit 9
bit 8
BYTE
X
X
X
X
X
X
X
X
LOW
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
BYTE
X
X
X
X
X
X
X
X
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.
The default bit values upon hard reset are highlighted below each register.
Table 2 - Internal I/O Space Mapping
BANK0
BANK1
BANK2
0
TCR
CONFIG
MMU COMMAND
2 EPH STATUS
BASE
PNR
4
RCR
IA0-1
FIFO PORTS
6
COUNTER
IA2-3
POINTER
8
MIR
IA4-5
DATA
A
MCR
GENERAL
DATA
C RESERVED (0)
CONTROL
INTERRUPT
E BANK SELECT
BANK SELECT
BANK SELECT
A special BANK (BANK7) exists to support the addition of external registers.
BANK3
MT0-1
MT2-3
MT4-5
MT6-7
MGMT
REVISION
ERCV
BANK SELECT
SMSC DS – LAN91C100FD REV. B
Page 18
Rev. 05/31/2000