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
41
5.6.4.2 Bulk In Endpoints
Bulk IN Endpoints are used to transfer data from the NET2272 local bus to a USB host. A bulk IN transaction from
a Bulk IN Endpoint consists of the following:
Stage
Packet Contents
Number of bytes
Source
IN Token
IN PID, address, endpoint, and CRC5
3
Host
Data (1/0)
DATA PID, N data bytes, and CRC16, or NAK or STALL
N+3
NET2272
Status
ACK
1
Host
The USB host initiates a Bulk IN transaction by sending an IN token to a Bulk IN endpoint. The Data IN Token
Interrupt bit is set when the IN token is recognized. If there is validated data in the endpoint’s buffer, 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).
Packet Validated
Amount of Data in Buffer
Action
0
< Max Packet Size
NAK to host
X
>= Max Packet Size
Return data to host
1
empty
Zero length packet to host
1
>0
Return data to host
After the packet has been sent to the host, the Data Packet Transmitted Interrupt bit is set.
If a packet is not successfully transmitted (Timeout status bit set), the Data Packet Transmitted Interrupt 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 the local CPU has stalled this endpoint by setting the Endpoint Halt bit, the NET2272 will respond to the IN token
with a STALL handshake to the host.
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