LAN9115 datasheet(40/114 Pages) MICROCHIP

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LAN9115

DS00002269A-page 40

 2005-2016 Microchip Technology Inc.

3.13.2.1

TX Command ‘A’

3.13.2.2

TX Command ‘B’

TABLE 3-11:

TX COMMAND 'A' FORMAT

Bits

Description

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.

30:26

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 LAN9115 will remove the extra DWORDs. This mechanism can be used to maintain cache

line alignment on host processors.

23:21

Reserved. These bits are reserved. Always write zeros to this field to provide future compatibility

20:16

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.

15:14

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.

10:0

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 LAN9115

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 LAN9115 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.

TABLE 3-12:

TX COMMAND 'B' FORMAT

Bits

Description

31:16

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.

15:14

Reserved. These bits are reserved. Always write zeros to this field to provide future compatibility.

Add CRC Disable. When set, the automatic addition of the CRC is disabled.

[25]

[24]

End Alignment

4-byte alignment

16-byte alignment

32-byte alignment

Reserved

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