Specification
NET2272 USB Peripheral Controller
______________________________________________________________________________
NetChip Technology, Inc., 2003
Patent Pending
335 Pioneer Way, Mountain View, California 94041
TEL (650) 526-1490
FAX (650) 526-1494
http://www.netchip.com
Rev 1.2, October 15, 2003
40
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 NET2272 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
3
Host
Data (1/0)
DATA PID, N data bytes, and CRC16
N+3
Host
Status
ACK, NAK, or STALL
1
NET2272
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 NET2272 will not store any data into
the buffer, and will respond with a STALL handshake to the host.
Chinese ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
