LAN9730 Datasheet, PDF (33/222 Pages) SMSC Corporation – High-Speed Inter-Chip (HSIC) USB 2.0

LAN9730/LAN9730i
4.3.1.2 Endpoint 2 (Bulk-Out)
The Bulk-Out Endpoint is controlled by the URX (USB Bulk-Out Receiver). The URX is responsible for receiving Ether-
net 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 exist. This means that the current Bulk-Out packet was accepted, but room does not
exist for a second packet. If less than 512 bytes exist, the URX responds with a NACK. The URX supports the PING
protocol.
FIGURE 4-3:
USB BULK-OUT TRANSACTION SUMMARY
Host Function
Out Token
Data Out
Transfer
ACK
NAK
NYET
STALL
Data Error
Ping
ACK
NAK
In the case where the Bulk-Out packet is errored, the URX does not respond to the host. The URX will request that the
FCT rewinds the packet. It is the host’s responsibility to retransmit the packet at a later time.
The FCT notifies the URX when it detects loss of sync. When this occurs, the URX stalls the Bulk-Out pipe. This is an
appropriate response, as loss of sync is a catastrophic error. This behavior is configurable via the Stall Bulk-Out Pipe
Disable (SBP) bit of the Hardware Configuration Register (HW_CFG) on page 125.
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DS00001946A-page 33