LAN9500 Datasheet, PDF (28/213 Pages) SMSC Corporation – USB 2.0 to 10/100 Ethernet Controller Promiscuous mode

LAN950x
FIGURE 5-2:
USB BULK IN TRANSACTION SUMMARY
Host Function
FS/HS HS Only
In Token
Data In Transfer
Zero Length
Packet Transfer
Stall
In Token Error
Ack
Data Error
Ack
5.3.1.2 Endpoint 2 (Bulk Out)
The Bulk Out Endpoint is controlled by the URX (USB Bulk Out Receiver). The URX is responsible for receiving Ethernet
data encapsulated over a USB Bulk Out packet. Unlike the UTX, the URX does not explicitly track Ethernet frames. It
views all received packets as purely USB data. The extraction of Ethernet frames is handled by the FCT and the Trans-
action Layer Interface (TLI).
The URX always simultaneously supports multiple Ethernet frames per USB packet, as well as a single Ethernet frame
per USB packet. No mechanism exists to select between modes.
The URX monitors the amount of free space in the TX FIFO. If at least 512 bytes of space exists, the URX can accept
an additional Bulk In frame and responds to a Bulk Out Token with an ACK or NYET. The NYET response is used when
less than 1024 bytes of free space exists. This means that the current Bulk Out packet was accepted, but room does
not exist for a second packet. If less than 512 bytes exists, the URX responds with a NAK. The URX supports the PING
protocol.
DS00001875A-page 28
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