LAN9211 datasheet(50/147 Pages) SMSC

50 / 147 page

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

Datasheet

Revision 2.9 (03-01-12)

SMSC LAN9211

DATASHEET

Figure 3.20, "TX Buffer Format", shows the TX Buffer as it is written into the LAN9211. It should be

noted that not all of the data shown in this diagram is actually stored in the TX data FIFO. This must

be taken into account when calculating the actual TX data FIFO usage. Please refer to Section 3.12.5,

"Calculating Actual TX Data FIFO Usage," on page 54 for a detailed explanation on calculating the

actual TX data FIFO usage.

3.12.2

TX Command Format

The TX command instructs the TX FIFO controller on handling the subsequent buffer. The command

precedes the data to be transmitted. The TX command is divided into two, 32-bit words; TX command

‘A’ and TX command ‘B’.

There is a 16-bit packet tag in the TX command ‘B’ command word. Packet tags may, if host software

desires, be unique for each packet (i.e., an incrementing count). The value of the tag will be returned

in the RX status word for the associated packet. The Packet tag can be used by host software to

uniquely identify each status word as it is returned to the host.

Both TX command ‘A’ and TX command ‘B’ are required for each buffer in a given packet. TX

command ‘B’ must be identical for every buffer in a given packet. If the TX command ‘B’ words do not

match, the Ethernet controller will assert the Transmitter Error (TXE) flag.

Figure 3.20 TX Buffer Format

TX Command 'A'

Offset + Data DWORD0

Last Data & PAD

1st

2nd

3rd

Last

Host Write

Order

Optional Pad DWORD0

Optional Pad DWORDn

TX Command 'B'

Optional offset DWORD0

Optional offset DWORDn

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