LAN9116 Datasheet, PDF (35/109 Pages) SMSC Corporation – Highly Efficient Single-Chip 10/100 Non-PCI Ethernet Controller

LAN9116
3.12.2.1 TX Command ‘A’
TABLE 3-11: TX COMMAND 'A' FORMAT
Bits
Description
31
30:26
Interrupt on Completion. When set, the TXDONE flag will be asserted when the current buffer has
been fully loaded into the TX FIFO. This flag may be optionally mapped to a host interrupt.
Reserved. These bits are reserved. Always write zeros to this field to provide future compatibility.
25:24
Buffer End Alignment. This field specifies the alignment that must be maintained on the last data
transfer of a buffer. The host will add extra DWORDs of data up to the alignment specified in the table
below. The LAN9116 will remove the extra DWORDs. This mechanism can be used to maintain cache
line alignment on host processors.
[25]
[24]
0
0
0
1
1
0
1
1
End Alignment
4-byte alignment
16-byte alignment
32-byte alignment
Reserved
23:21
20:16
15:14
13
12
11
10:0
Reserved. These bits are reserved. Always write zeros to this field to provide future compatibility
Data Start Offset (bytes). This field specifies the offset of the first byte of TX data. The offset value
can be anywhere from 0 bytes to 31 a Byte offset.
Reserved. These bits are reserved. Always write zeros to this field to provide future compatibility
First Segment. When set, this bit indicates that the associated buffer is the first segment of the packet.
Last Segment. When set, this bit indicates that the associated buffer is the last segment of the packet
Reserved. These bits are reserved. Always write zeros to this field to provide future compatibility.
Buffer Size (bytes). This field indicates the number of bytes contained in the buffer following this
command. This value, along with the Buffer End Alignment field, is read and checked by the LAN9116
and used to determine how many extra DWORD’s were added to the end of the Buffer. A running
count is also maintained in the LAN9116 of the cumulative buffer sizes for a given packet. This
cumulative value is compared against the Packet Length field in the TX command ‘B’ word and if they
do not correlate, the TXE flag is set.
Note: The buffer size specified does not include the buffer end alignment padding or data start off-
set added to a buffer.
3.12.2.2 TX Command ‘B’
TABLE 3-12: TX COMMAND 'B' FORMAT
Bits
Description
31:16
15:14
Packet Tag. The host should write a unique packet identifier to this field. This identifier is added to
the corresponding TX status word and can be used by the host to correlate TX status words with their
corresponding packets.
Note: The use of packet tags is not required by the hardware. This field can be used by the LAN
software driver for any application. Packet Tags is one application example.
Reserved. These bits are reserved. Always write zeros to this field to provide future compatibility.
13
Add CRC Disable. When set, the automatic addition of the CRC is disabled.
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DS00002268A-page 35