High Performance Single-Chip 10/100 Non-PCI Ethernet Controller
Datasheet
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, LAN9118 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 LAN9118 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 56. For more information
on the RX_DUMP bit, please refer to Section 5.3.7, "RX_CFG—Receive Configuration Register," on
page 75.
3.13.2
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. It is assumed that the host has previously read the associated status word from the RX
status FIFO, to ascertain the data size and any error conditions.
Host Read
Order
31
0
Optional offset DWORD0
1st
2nd
.
.
Optional offset DWORDn
ofs + First Data DWORD
.
.
.
.
Last Data DWORD
Optional Pad DWORD0
.
.
Optional Pad DWORDn
Last
Figure 3.18 RX Packet Format
SMSC LAN9118
Revision 1.3 (05-31-07)
DATA5S5HEET
SMSC [ SMSC CORPORATION ]
