LAN9211 datasheet(62/147 Pages) SMSC

62 / 147 page

High-Performance Small Form Factor Single-Chip Ethernet Controller with HP Auto-MDIX Support

Datasheet

Revision 2.9 (03-01-12)

SMSC LAN9211

DATASHEET

3.13.1.1

Receive Data FIFO Fast Forward

The RX data path implements an automatic data discard function. Using the RX data FIFO Fast

Forward bit (RX_FFWD) in the RX_DP_CTRL register, the host can instruct the LAN9211 to skip the

packet at the head of the RX data FIFO. The RX data FIFO pointers are automatically incremented to

the beginning of the next RX packet.

When performing a fast-forward, there must be at least 4 DWORDs of data in the RX data FIFO for

the packet being discarded. For less than 4 DWORDs do not use RX_FFWD. In this case data must

be read from the RX data FIFO and discarded using standard PIO read operations.

After initiating a fast-forward operation, do not perform any reads of the RX data FIFO until the

RX_FFWD bit is cleared. Other resources can be accessed during this time (i.e., any registers and/or

the other three FIFOs). Also note that the RX_FFWD will only fast-forward the RX data FIFO, not the

RX status FIFO.

The receiver does not have to be stopped to perform a fast-forward operation.

3.13.1.2

Force Receiver Discard (Receiver Dump)

In addition to the Receive data Fast Forward feature, LAN9211 also implements a receiver "dump"

feature. This feature allows the host processor to flush the entire contents of the RX data and RX

status FIFOs. When activated, the read and write pointers for the RX data and status FIFOs will be

returned to their reset state. To perform a receiver dump, the LAN9211 receiver must be halted. Once

the receiver stop completion is confirmed, the RX_DUMP bit can be set in the RX_CFG register. The

RX_DUMP bit is cleared when the dump is complete. For more information on stopping the receiver,

please refer to Section 3.13.4, "Stopping and Starting the Receiver," on page 65. For more information

on the RX_DUMP bit, please refer to Section 5.3.7, "RX_CFG—Receive Configuration Register," on

page 85.

LAN9211 数据表(PDF) 62 Page - SMSC Corporation