Datasheet

16-bit Non-PCI Small Form Factor 10/100 Ethernet Controller with Variable Voltage I/O & HP Auto-MDIX Support
Datasheet
Revision 2.9 (03-01-12) 50 SMSC LAN9220
DATASHEET
3.12.1 TX Buffer Format
TX buffers exist in the host’s memory in a given format. The host writes a TX command word into the
TX data buffer before moving the Ethernet packet data. The TX command A and command B are 32-
bit values that are used by the LAN9220 in the handling and processing of the associated Ethernet
packet data buffer. Buffer alignment, segmentation and other packet processing parameters are
included in the command structure. The following diagram illustrates the buffer format.
Figure 3.19 Simplified Host TX Flow Diagram
Idle
Check
available
FIFO
space
init
Write
TX
Command
Write
Buffer
Last Buffer in
Packet
Not Last Buffer
Write
Start
Padding
(optional)
Read TX
Status
(optional)
TX Status
Available