NET2270 datasheet(37/90 Pages) ETC2

37 / 90 page

Specification

NET2270 USB Interface Controller

______________________________________________________________________________

 NetChip Technology, Inc., 2003

335 Pioneer Way, Mountain View, California 94041

TEL (650) 526-1490

FAX (650) 526-1494

http://www.netchip.com

Rev 3.6, April 17, 2003

5.6.4 Bulk Endpoints

Bulk endpoints are used for guaranteed error-free delivery of large amounts of data between a host and device. Bulk

endpoints are unidirectional, with the direction defined by the endpoint configuration registers.

5.6.4.1 Bulk Out Transactions

Bulk Out endpoints are used to transfer data from a USB host to the NET2270 local bus. A bulk OUT transaction to

a Bulk Out endpoint consists of the following:

Stage

Packet Contents

Number of bytes

Source

OUT Token

OUT PID, address, endpoint, and CRC5

Host

Data (1/0)

DATA PID, N data bytes, and CRC16

N+3

Host

Status

ACK, NAK, or STALL

NET2270

The USB host initiates a Bulk OUT transaction by sending an OUT token to a Bulk OUT endpoint. The Data OUT

Token Interrupt bit is set when the OUT token is recognized. The bytes corresponding to the Data stage are stored

into the endpoint’s buffer. If the buffer is full when another packet is transferred from the host, the packet will be

discarded and the USB OUT NAK Sent status bit will be set. At the completion of the packet, a NAK handshake

will be returned to the host, indicating that the packet could not be accepted.

All USB data passes through the endpoint’s buffer to the local bus. The CPU waits until the Data Packet Received

Interrupt occurs before reading the data from the buffer.

If a packet is not successfully received (USB OUT NAK Sent or Timeout status bits set), the Data Packet Received

Interrupt bit will not be set, and the data will be automatically flushed from the buffer. The host will re-send the

same packet again. This process is transparent to the local CPU.

If the local CPU has stalled this endpoint by setting the Endpoint Halt bit, the NET2270 will not store any data into

the buffer, and will respond with a STALL handshake to the host.

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