LAN9211 datasheet(48/147 Pages) SMSC

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High-Performance Small Form Factor Single-Chip Ethernet Controller with HP Auto-MDIX Support

Datasheet

Revision 2.9 (03-01-12)

SMSC LAN9211

DATASHEET

‘A’ and TX command ‘B’). The TX command instructs the LAN9211 on the handling of the associated

buffer. Packet boundaries are delineated using control bits within the TX command.

The host provides a 16-bit Packet Tag field in the TX command. The Packet Tag value is appended

to the corresponding TX status DWORD. All Packet Tag fields must have the same value for all buffers

in a given packet. If tags differ between buffers in the same packet the TXE error will be asserted. Any

value may be chosen for a Packet Tag as long as all tags in the same Packet are identical. Packet

Tags also provide a method of synchronization between transmitted packets and their associated

status. Software can use unique Packet Tags to assist with validating matching status completions.

Note 3.14 The use of packet tags is not required by the hardware. This is a software LAN driver only

application example for use of this field.

A Packet Length field in the TX command specifies the number of bytes in the associated packet. All

Packet Length fields must have the same value for all buffers in a given packet. Hardware compares

the Packet Length field and the actual amount of data received by the Ethernet controller. If the actual

packet length count does not match the Packet Length field as defined in the TX command, the

Transmitter Error (TXE) flag is asserted.

The LAN9211 can be programmed to start payload transmission of a buffer on a byte boundary by

setting the “Data Start Offset” field in the TX command. The “Data Start Offset” field points to the actual

start of the payload data within the first 8 DWORDs of the buffer. Data before the “Data Start Offset”

pointer will be ignored. When a packet is split into multiple buffers, each successive buffer may begin

on any arbitrary byte.

The LAN9211 can be programmed to strip padding from the end of a transmit packet in the event that

the end of the packet does not align with the host burst boundary. This feature is necessary when the

LAN9211 is operating in a system that always performs multi-word bursts. In such cases the LAN9211

must guarantee that it can accept data in multiples of the Burst length regardless of the actual packet

length. When configured to do so, the LAN9211 will accept extra data at the end of the packet and will

remove the extra padding before transmitting the packet. The LAN9211 automatically removes data up

to the boundary specified in the Buffer End Alignment field specified in each TX command.

The host can instruct the LAN9211 to issue an interrupt when the buffer has been fully loaded into the

TX FIFO contained in the LAN9211 and transmitted. This feature is enabled through the TX command

‘Interrupt on Completion’ field.

Upon completion of transmission, irrespective of success or failure, the status of the transmission is

written to the TX status FIFO. TX status is available to the host and may be read using PIO operations.

An interrupt can be optionally enabled by the host to indicate the availability of a programmable

number TX status DWORDS.

Before writing the TX command and payload data to the TX FIFO, the host must check the available

TX FIFO space by performing a PIO read of the TX_FIFO_INF register. The host must ensure that it

does not overfill the TX FIFO or the TX Error (TXE) flag will be asserted.

The host proceeds to write the TX command by first writing TX command ‘A’, then TX command ‘B’.

After writing the command, the host can then move the payload data into the TX FIFO. TX status

DWORD’s are stored in the TX status FIFO to be read by the host at a later time upon completion of

the data transmission onto the wire.

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