lan9221 Standard Microsystems Corp., lan9221 Datasheet - Page 51

• Manufacturer Part Number: lan9221
• Description: High-performance 16-bit Non-pci 10/100 Ethernet Controller With Variable Voltage I/o
• Manufacturer: Standard Microsystems Corp.

High-Performance 16-bit Non-PCI 10/100 Ethernet Controller with Variable Voltage I/O
Datasheet
SMSC LAN9221/LAN9221i
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 LAN9221/LAN9221i 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.
Last Buffer in
Figure 3.13 Simplified Host TX Flow Diagram
Packet
Command
DATASHEET
(optional)
available
Padding
Check
space
Buffer
Write
FIFO
Write
Write
Start
Idle
init
TX
51
TX Status
Available
Not Last Buffer
(optional)
Read TX
Status
Revision 2.6 (12-04-08)