NET2890 datasheet(17/73 Pages) ETC

17 / 73 page

Specification

NET2890 USB Interface Controller

____________________________________________________________________________________

NetChip Technology, Inc., 1999

335 Pioneer Way, Mountain View, California 94041

TEL (650) 526-1490

FAX (650) 526-1494

http://www.netchip.com

Rev 2.0, Draft 9, July 16, 1999

4. Functional Description

4.1 USB Interface

The NET2890 is a USB function device, and as a result is always a slave to the USB host. The bit and

packet level protocols, as well as the electrical interface of the NET2890, conform to USB Specification

Version 1.0. All USB data transfers to and from the NET2890 USB port are initiated by the USB host. The

NET2890 can be configured for up to 4 endpoints, in addition to Endpoint 0. Each endpoint can be an

isochronous, bulk or interrupt type. The configuration registers are used to program the characteristics of

each endpoint.

4.2 USB Protocol

The packet protocol of the USB bus consists of tokens, packets, transactions, and transfers.

4.2.1 Tokens

Tokens are a type of Packet Identifier (PID), and follow the sync byte at the beginning of a token packet.

The four types of tokens are OUT, IN, SOF, and SETUP.

4.2.2 Packets

There are four types of packets: start-of-frame (SOF), token, data, and handshake. Each packet begins with

a sync byte and a Packet Identifier (PID). The other fields vary depending on the type of packet.

An SOF packet consists of the following fields:

•

Sync byte (8-bits)

•

Packet Identifier (8-bits)

•

Frame Number (11-bits)

•

CRC (5-bits)

A token packet consists of the following fields:

•

Sync byte (8-bits)

•

Packet Identifier (8-bits)

•

Address (7-bits)

•

Endpoint (4-bits)

•

CRC (5-bits)

A data packet consists of the following fields: Data packets are always preceded by a token packet.

•

Sync byte (8-bits)

•

Packet Identifier (8-bits)

•

Data (n bytes)

•

CRC (16-bits)

A handshake packet consists of the following fields:

•

Sync byte (8-bits)

•

Packet Identifier (8-bits)

4.2.3 Transaction

A transaction consists of a token packet, optional data packet(s), and a handshake packet.

4.2.4 Transfer

A transfer consists of one or more transactions. Control transfers consist of a setup transaction, optional

data transactions, and a handshake (status) transaction.

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NET2890 数据表(PDF) 17 Page - List of Unclassifed Manufacturers

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