net2890 ETC-unknow, net2890 Datasheet - Page 17

• Manufacturer Part Number: net2890
• Description: Interface Controller
• Manufacturer: ETC-unknow

Specification
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:
A token packet consists of the following fields:
A data packet consists of the following fields: Data packets are always preceded by a token packet.
A handshake packet consists of the following fields:
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.
____________________________________________________________________________________
Sync byte (8-bits)
Packet Identifier (8-bits)
Frame Number (11-bits)
CRC (5-bits)
Sync byte (8-bits)
Packet Identifier (8-bits)
Address (7-bits)
Endpoint (4-bits)
CRC (5-bits)
Sync byte (8-bits)
Packet Identifier (8-bits)
Data (n bytes)
CRC (16-bits)
Sync byte (8-bits)
Packet Identifier (8-bits)
335 Pioneer Way, Mountain View, California 94041
TEL [phone] FAX [phone]
NetChip Technology, Inc., 1999
Rev 2.0, Draft 9, July 16, 1999
http://www.netchip.com
NET2890 USB Interface Controller
17