Two Port 10/100 Managed Ethernet Switch with 16-Bit Non-PCI CPU Interface

 

 

 

 

 

 

Datasheet

 

Both TX command ‘A’ and TX command ‘B’ are required for each buffer in a given packet. TX

 

command ‘B’ must be identical for every buffer in a given packet. If the TX command ‘B’ words do not

 

match, the Ethernet controller will assert the Transmitter Error (TXE) flag.

9.8.2.1

TX Command ‘A’

 

 

 

 

 

 

 

Table 9.10 TX Command 'A' Format

 

 

 

 

 

 

 

BITS

 

 

 

 

DESCRIPTION

 

 

 

 

 

 

31

Interrupt on Completion (IOC). When set, the TX_IOC bit will be asserted in the Interrupt Status

 

Register (INT_STS) when the current buffer has been fully loaded into the TX FIFO.

 

 

 

 

 

 

30:26

Reserved. These bits are reserved. Always write zeros to this field to guarantee 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 LAN9311/LAN9311i will remove the extra DWORDs. This mechanism can be used

 

to maintain cache line alignment on host processors.

 

 

 

 

 

 

 

 

[25]

 

[24]

End Alignment

 

 

 

 

 

 

 

 

 

 

0

 

0

4-byte alignment

 

 

 

 

 

 

 

 

 

 

0

 

1

16-byte alignment

 

 

 

 

 

 

 

 

 

 

1

 

0

32-byte alignment

 

 

 

 

 

 

 

 

 

 

1

 

1

Reserved

 

 

 

 

 

 

 

 

 

 

 

 

 

 

23:21

Reserved. These bits are reserved. Always write zeros to this field to guarantee 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 a 31 byte offset.

 

 

 

 

 

 

15:14

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

 

 

 

 

 

 

13

First Segment (FS). When set, this bit indicates that the associated buffer is the first segment of the

 

packet.

 

 

 

 

 

 

 

 

 

 

12

Last Segment. When set, this bit indicates that the associated buffer is the last segment of the

 

packet

 

 

 

 

 

 

 

 

 

 

11

Reserved. These bits are reserved. Always write zeros to this field to guarantee 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

 

LAN9311/LAN9311i and used to determine how many extra DWORDs were added to the end of the

 

Buffer. A running count is also maintained in the LAN9311/LAN9311i 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

 

offset added to a buffer.

 

 

 

 

 

 

 

 

 

Revision 1.4 (08-19-08)

126

SMSC LAN9311/LAN9311i

 

DATASHEET