DP83820 datasheet(52/87 Pages) NSC

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4.0 Register Set (Continued)

4.2.16 Receive Configuration Register

This register is used to set the receive configuration for DP83820. Receive properties such as accepting error packets,

runt packets, setting the receive drain threshold etc. are controlled here

Tag: RXCFG

Size: 32 bits

Hard Reset: 00000004h

Offset: 0038h

Access: Read Write

Soft Reset: 00000004h

bit

tag

description

usage

AEP

Accept Errored Packets

When set to 1, all packets with CRC or alignment errors will be accepted.

When set to 0, all packets with CRC or alignment errors will be rejected if

possible. Note that depending on the type of error, some packets may be

received with errors, regardless of the setting of AEP. These errors will be

indicated in the CMDSTS field of the last descriptor in the packet.

ARP

Accept Runt Packets

When set to 1, all packets under 64 bytes in length without errors are

accepted. When this bit is 0, all packets less than 64 bytes in length will be

rejected if possible.

STRIPCRC

Strip CRC

When set to a 1, the CRC will be stripped from the receive packet and the

byte count adjusted appropriately.

RX_FD

Receive Full Duplex

When set to 1, data received simultaneously to a local transmission (such

as during a PMD loopback or full duplex operation) will be accepted as valid

received data. When set to 0 (default), all data received simultaneous to a

local transmit will be rejected. This bit must be set to 1 for PMD loopback

and full duplex operation.

ALP

Accept Long Packets

When set to 1, all packets > 1518 bytes in length and <= 65527 bytes will

be treated as normal receive packets, and will not be tagged as long or

error packets. All packets > 65527 bytes in length will be truncated at 65528

bytes and either rejected from the FIFO, or tagged as long packets. Care

must be taken when accepting long packets to ensure that buffers provided

are of adequate length. When ALP is set to 0, packets larger than 1518

bytes (CRC inclusive) will be truncated at 1514 bytes, and rejected if

possible.

AIRL

Accept In-Range Length

Errored Packets

When set to 1, packets with Length/Type fields that do not match the data

length of the packet will be accepted. When set to 0, packets with

Length/Type fields that do not match the data length of the packet will be

rejected. In-Range Length checking only occurs if the Length/Type field is a

valid length.

25-23

unused

22-20

MXDMA

Max DMA Burst Size per Rx

DMA Burst

This field sets the maximum size of receive DMA data bursts according to

the following table:

000 = 256 32-bit words (1024 bytes)

001 = 2 32-bit words (8 bytes)

010 = 4 32-bit words (16 bytes)

011 = 8 32-bit words (32 bytes)

100 = 16 32-bit words (64 bytes)

101 = 32 32-bit words (128 bytes)

110 = 64 32-bit words (256 bytes)

111 = 128 32-bit word (512 bytes)

19-6

unused

DP83820 Datasheet(PDF) 52 Page - National Semiconductor (TI)

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