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High Performance Two Port 10/100 Managed Ethernet Switch with 32-Bit Non-PCI CPU Interface
Datasheet
Revision 1.4 (08-19-08) 180 SMSC LAN9312
DATASHEET
14.2.2 Host MAC & FIFO’s
This section details the Host MAC and TX/RX FIFO related System CSR’s.
These Host Bus Interface accessible registers allow for the configuration of the TX/RX FIFO’s, Host
MAC and indirect access to the complete set of Host MAC CSR’s. The Host MAC CSR’s are
accessible through the Host Bus Interface via the Host MAC CSR Interface Command Register
(MAC_CSR_CMD) and Host MAC CSR Interface Data Register (MAC_CSR_DATA).
Note: For more information on the TX/RX FIFO’s, refer to Section 14.1, "TX/RX FIFO Ports".
Note: The full list of Host MAC CSR’s are described in Section 14.3, "Host MAC Control and Status
Registers," on page 269. For more information on the Host MAC, refer to Chapter 9, "Host
MAC," on page 112.
14.2.2.1 Receive Configuration Register (RX_CFG)
This register controls the Host MAC receive engine.
Offset: 06Ch Size: 32 bits
BITS DESCRIPTION TYPE DEFAULT
31:30 RX End Alignment (RX_EA)
This field specifies the alignment that must be maintained on the last data
transfer of a buffer. The LAN9312 will add extra DWORD’s of data up to
the alignment specified in the table below. The host is responsible for
removing these extra DWORD’s. This mechanism can be used to maintain
cache line alignment on host processors.
Note: The desired RX End Alignment must be set before reading a
packet. The RX End Alignment can be changed between reading
receive packets, but must not be changed if the packet is partially
read.
R/W 00b
29:28
RESERVED RO -
27:16
RX DMA Count (RX_DMA_CNT)
This 12-bit field indicates the amount of data, in DWORD’s, to be
transferred out of the RX Data FIFO before asserting the RX DMA Interrupt
(RXD_INT). After being set, this field is decremented for each DWORD of
data that is read from the RX Data FIFO. This field can be overwritten with
a new value before it reaches zero.
R/W 000h
15
Force RX Discard (RX_DUMP)
When a 1 is written to this bit, the RX Data and Status FIFO’s are cleared
of all pending data and the RX data and status pointers are cleared to zero.
Note: Please refer to Section 9.9.1.2, "Force Receiver Discard (Receiver
Dump)," on page 134 for a detailed description regarding the use
of RX_DUMP.
WO
SC
0b
BIT
VALUES
[31:30] END ALIGNMENT
00 4-Byte Alignment
01 16-Byte Alignment
10 32-Byte Alignment
11 RESERVED