LAN89218AQ Standard Microsystems (SMSC), LAN89218AQ Datasheet - Page 61

• Manufacturer Part Number: LAN89218AQ
• Manufacturer: Standard Microsystems (SMSC)

Specifications of LAN89218AQ

• Lead Free Status / RoHS Status: Compliant

High Performance Single-Chip 10/100 Ethernet Controller for Automotive Applications
Datasheet
SMSC LAN89218
3.12.5
3.12.6
3.12.6.1
Calculating Actual TX Data FIFO Usage
The following rules are used to calculate the actual TX data FIFO space consumed by a TX Packet:
Transmit Examples
TX 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:
Buffer 1:
Buffer 2:
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'
When TX checksum is enabled, the 4-byte TX checksum preamble is written into TX Data FIFO.
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
7-Byte “Data Start Offset”
79-Bytes of payload data
16-Byte “Buffer End Alignment”
0-Byte “Data Start Offset”
15-Bytes of payload data
16-Byte “Buffer End Alignment”
10-Byte “Data Start Offset”
17-Bytes of payload data
16-Byte “Buffer End Alignment”
DATASHEET
61
Revision 1.3 (02-23-10)