NET2270 datasheet(41/90 Pages) ETC2

41 / 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

5.7.2 OUT Endpoint Buffers

When receiving data, the NET2270 will NAK the host (indicating that it cannot accept the data) if either the buffer

runs out of room, or if both the NAK OUT Packets Mode bit and the NAK OUT Packets bits are set. If the packets

received are of maximum size, then additional packets can be received independently of the NAK OUT Packets

Mode bit. This bit will only cause additional OUT packets to be NAKed if the last packet received was a short

packet.

If NAK OUT Packets Mode is true (blocking mode), USB OUT transfers can overlap with the local CPU unloading

the data using the following sequence:

•

Local CPU responds to the Data Packet Received Interrupt and reads the EP_AVAIL register so it knows how

many bytes are in the current packet.

•

Local CPU clears the Data Packet Received Interrupt and the NAK OUT Packets bit, allowing the next packet

to be received.

•

Now the local CPU can unload data from the buffer while the next USB OUT transaction is occurring.

If NAK OUT Packets Mode is false (non-blocking mode), the NET2270 will accept packets as long as there is room

for the complete packet in the next available buffer. Note that there are no indications of packet boundaries when

there are multiple packets in the buffers in a double-buffered configuration.

NET2270 数据表(PDF) 41 Page - List of Unclassifed Manufacturers