NET2890 datasheet(26/73 Pages) ETC

26 / 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

4.5.4.2 Bulk In Endpoints

Bulk IN Endpoints are used to transfer data from the NET2890 local bus to a USB host. A bulk read

transaction from a Bulk IN Endpoint consists of the following:

Stage

Packet Contents

# of

bytes

Source

IN Token

IN PID, address, endpoint, and CRC5

Host

Data (1/0)

DATA PID, N data bytes, and CRC16,

or NAK or STALL

N+3

NET2890

Status

ACK

Host

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

Token Interrupt status bit is set when the IN token is recognized. If this interrupt is enabled, the local

interrupt IRQ# pin is asserted. If there is data in the endpoint’s FIFO, it is returned to the host. If the

endpoint has no data to return, it returns either a zero length packet (signaling that there is no more data

available) or a NAK handshake (the data is not available yet), depending on the FIFO Valid and FIFO

Valid Mode bits.

FIFO

Valid

Mode

FIFO

Valid

Bit

End of

Transfer

Response Bit

Size of

Packet

Amount of Data in

FIFO

Action

empty

NAK to host

Maximum

empty

Zero length packet to host

< Maximum

empty

NAK to host

empty

Zero length packet to host

Return data to host

< Max Packet Length

NAK to host

>= Max Packet Length

Return data to host

empty

Zero length packet to host

Return data to host

After the packet has been sent to the host, the Data Packet Transmitted Interrupt status bit is set. If this

interrupt is enabled, the local interrupt IRQ# pin is asserted. If retries are disabled, the local CPU should

check the USB IN ACK Sent, USB IN NAK Sent, and Timeout status bits to determine if the packet was

successfully transmitted.

•

If a packet is not successfully transmitted (Timeout status bit set) and retries are enabled, the Data

Packet Transmitted Interrupt status bit will not be set, and the same packet is sent to the host when

another IN token is received. The retry operation is transparent to the local CPU.

•

If a packet is not successfully transmitted (Timeout status bit set) and retries are disabled, the Data

Packet Transmitted Interrupt status bit will be set. The local CPU needs to flush the FIFO and

reload the packet for the next IN token.

•

If the host tries to read more data than was requested in the setup packet, the local CPU should set the

STALL bit for the endpoint.

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NET2890 数据表(PDF) 26 Page - List of Unclassifed Manufacturers

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