EVB9311 SMSC, EVB9311 Datasheet - Page 135

• Manufacturer Part Number: EVB9311
• Description: EVALUATION BOARD LAN9311-NU
• Manufacturer: SMSC
• Series: 0133r

Specifications of EVB9311

• Main Purpose: Interface, Ethernet
• Embedded: No
• Utilized Ic / Part: LAN9311
• Primary Attributes: 2 Ports, 100BASE-TX/10BASE-T, Managed
• Secondary Attributes: 2 PHYs with HP Auto-MDIX, Auto- Flow Control, 32-bit CRC, MDI/MDI-X
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 638-1076

Two Port 10/100 Managed Ethernet Switch with 16-Bit Non-PCI CPU Interface
Datasheet
SMSC LAN9311/LAN9311i
9.9.1.1
9.9.1.2
9.9.2
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
instruct the LAN9311/LAN9311i 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 cases with 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 FIFO’s). Also note that the RX_FFWD will only fast-forward the RX Data FIFO, not the
RX Status FIFO. After an RX fast-forward operation the RX status must still be read from the RX Status
FIFO.
The receiver does not have to be stopped to perform a fast-forward operation.
Force Receiver Discard (Receiver Dump)
In addition to the Receive data Fast Forward feature, LAN9311/LAN9311i 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 FIFO’s will
be returned to their reset state. To perform a receiver dump, the LAN9311/LAN9311i receiver must be
halted. Once the receiver stop completion is confirmed, the RX_DUMP bit can be set in the
Configuration Register
information on stopping the receiver, please refer to
Receiver". For more information on the RX_DUMP bit, please refer to
Configuration Register (RX_CFG)," on page
RX Packet Format
The RX status words can be read from the RX Status FIFO port, while the RX data packets can be
read from the RX Data FIFO. RX data packets are formatted in a specific manner before the host can
read them as shown in
status word from the RX Status FIFO, to ascertain the data size and any error conditions.
(RX_CFG). The RX_DUMP bit is cleared when the dump is complete. For more
Host Read
Order
Figure
Last
2nd
1st
Figure 9.9 RX Packet Format
9.9. It is assumed that the host has previously read the associated
Receive Datapath Control Register
DATASHEET
31
ofs + First Data DWORD
Optional offset DWORDn
Optional offset DWORD0
Optional Pad DWORDn
Optional Pad DWORD0
Last Data DWORD
135
181.
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Section 9.9.4, "Stopping and Starting the
0
(RX_DP_CTRL), the host can
Section 14.2.2.1, "Receive
Revision 1.7 (06-29-10)
Receive