AX88140AP datasheet(28/46 Pages) ASIX

28 / 46 page

AX88140A

PRELIMINARY

ASIX ELECTRONICS CORPORATION

Tab - 26 REG11 General -Purpose Timer Register Description

4.2.12 General -Purpose Port Register (REG12)

Field

R/W/C

Description

31:9

Reserved.--Written as “0” for future compatibility concern.

Indicate next write REG12<7:0> is use

for define General purpose port in/out

direction.

R/W

GPC - General Purpose Control .

When a hardware reset is initiated, all gep pins

become input pins.

Indicate next write REG12<7:0> is use

for read/write general purpose port data.

7:0

R/W

MD - General Purpose Mode and Data

Tab - 27 REG12 General -Purpose Port Register Description

4.2.13 Filtering Index (REG13)

FIELD

R/W/C

DESCRIPTION

31:6

Reserved.--Written as “0” for future compatibility concern.

5:0

R/W

FI - Filtering Index

When writing data to filtering buffer, uses filtering index register REG13 to point the position (buffer

number) in filtering buffer. The valid value is between 0 and 3.

Tab - 28 REG13 Filtering Index Register Description

4.2.14 Filtering data (REG14)

FIELD

R/W/C

DESCRIPTION

31:0

R/W

FD - Filtering Data

By indexed by filtering index register REG13, write the filtering data register REG14 to put filtering

address/hash table into filtering buffer..

Tab - 29 REG14 Filtering Data Register Description

Filtering Buffer

The AX88140A stores one Ethernet address for local physical address and filters the packets

with multicast addresses by 64 bits array. For any incoming frame with a multicast destination

address, the AX88140A applies the standard Ethernet cyclic redundancy check function to the

destination address, then uses the most significant 6 bits of the result as a bit index into the table. If

the indexed bit is set, the frame is accepted. If the bit is reset, the frame is rejected.

Description of Filtering Buffer

BUFFER

NUMBER

DESCRIPTION

BYTE 0 - 3 OF LOCAL PHYSICAL ADDRESS

BYTE 4 - 5 OF LOCAL PHYSICAL ADDRESS IN THE LEAST SIGNIFICANT WORD

BIT 0 - 31 OF MULTICAST ADDRESS FILTERING TABLE

Bit 32 - 63 of multicast address filtering table

Tab - 30 Description of Filtering Buffer

Layout of Filtering Buffer

BUFFER

NUMBER

BYTE 3

BYTE 2

BYTE 1

BYTE 0

PHYSICAL

ADDRESS BYTE 3

PHYSICAL ADDRESS

BYTE 2

PHYSICAL ADDRESS

BYTE 1

PHYSICAL ADDRESS

BYTE 0

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