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

Datasheet

BITS

DESCRIPTION

 

 

8

Excessive Collisions. When set, this bit indicates that the transmission was aborted after 16

 

collisions while attempting to transmit the current packet.

 

 

7

Reserved. This bit is reserved. Always write zeros to this field to guarantee future compatibility.

 

 

6:3

Collision Count. This counter indicates the number of collisions that occurred before the packet was

 

transmitted. It is not valid when excessive collisions (bit 8) is also set.

 

 

2

Excessive Deferral. If the deferred bit is set in the control register, the setting of the excessive

 

deferral bit indicates that the transmission has ended because of a deferral of over 24288 bit times

 

during transmission.

 

 

1

Reserved. This bit is reserved. Always write zeros to this field to guarantee future compatibility

 

 

0

Deferred. When set, this bit indicates that the current packet transmission was deferred.

 

 

9.8.5 Calculating Actual TX Data FIFO Usage

The following rules are used to calculate the actual TX Data FIFO space consumed by a TX Packet:

„TX command 'A' is stored in the TX Data FIFO for every TX buffer

„TX command 'B' is written into the TX Data FIFO when the First Segment (FS) bit is set in TX command 'A'

„Any DWORD-long data added as part of the “Data Start Offset” is removed from each buffer before the data is written to the TX Data FIFO. Any data that is less than 1 DWORD is passed to the TX Data FIFO.

„Payload from each buffer within a Packet is written into the TX Data FIFO.

„Any DWORD-long data added as part of the End Padding is removed from each buffer before the data is written to the TX Data FIFO. Any end padding that is less than 1 DWORD is passed to the TX Data FIFO

9.8.6Transmit Examples

9.8.6.1TX Example 1

In this example a single, 111-Byte Ethernet packet will be transmitted. This packet is divided into three buffers. The three buffers are as follows:

Buffer 0:

„7-Byte “Data Start Offset”

„79-Bytes of payload data

„16-Byte “Buffer End Alignment”

Buffer 1:

„0-Byte “Data Start Offset”

„15-Bytes of payload data

„16-Byte “Buffer End Alignment”

Buffer 2:

„10-Byte “Data Start Offset”

„17-Bytes of payload data

„16-Byte “Buffer End Alignment”

SMSC LAN9311/LAN9311i

129

Revision 1.4 (08-19-08)

 

DATASHEET