SMSC LAN9312 - Manual (Page 130)

High Performance Two Port 10/100 Managed Ethernet Switch with 32-Bit Non-PCI CPU Interface
Datasheet
Revision 1.4 (08-19-08) 130 SMSC LAN9312
DATASHEET
9.8.6.2 TX Example 2
In this example, a single 183-Byte Ethernet packet will be transmitted. This packet is in a single buffer
as follows:
„ 2-Byte “Data Start Offset”
„ 183-Bytes of payload data
„ 4-Byte “Buffer End Alignment”
Figure 9.6 illustrates the TX command structure for this example, and also shows how data is passed
to the TX Data FIFO. Note that the packet resides in a single TX Buffer, therefore both the FS and LS
bits are set in TX command ‘A’.
Figure 9.6 TX Example 2
TX Command 'A'
0 31
TX Command 'B'
Data Written to the
Memory Mapped
TX Data FIFO Port
TX Command 'B'
183-Byte Payload Data
Data Start Offset = 6
First Segment = 1
Last Segment = 1
Buffer Size =183
Packet Length = 183
TX Command 'A'
TX Command 'B'
Data Passed to the
TX Data FIFO
Buffer End Alignment = 0
3B End Padding
TX Command 'A'
6-Byte Data Start Offset
183-Byte Payload Data
NOTE: Extra bytes between buffers
are not transmitted