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
39
5.6.5 Interrupt Endpoints
Interrupt endpoints are used for sending or receiving small amounts of data to the host with a bounded service
period.
5.6.5.1 Interrupt Out Transactions
Interrupt Out endpoints are used to transfer data from a USB host to the NET2270 local bus. An interrupt OUT
transaction to an Interrupt 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
NET2270
The behavior of an Interrupt OUT endpoint is the same as a Bulk OUT endpoint, except for the toggle bit. If the
Interrupt Mode bit is cleared, the toggle bit of the Interrupt OUT endpoint is initialized to 0 (DATA0 PID), and
behaves the same as a Bulk OUT endpoint. If the Interrupt Mode bit is set, the toggle bit of the Interrupt OUT
endpoint changes after each data packet is received from the host, without regard to the Status stage. Note that the
PING protocol is not allowed for Interrupt OUT endpoints, as per the USB specification.
5.6.5.2 Interrupt In Endpoints
An Interrupt IN endpoint is polled at a rate which is specified in the endpoint descriptor. An interrupt transaction
from an Interrupt 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
N+3
NET2270
Status
ACK
1
Host
The behavior of an Interrupt IN endpoint is the same as a Bulk IN endpoint, except for the toggle bit. If the
Interrupt Mode bit is cleared, the toggle bit of the Interrupt IN endpoint is initialized to 0 (DATA0 PID), and
behaves the same as a Bulk IN endpoint. An interrupt endpoint may be used to communicate rate feedback
information for certain types of isochronous functions. To support this mode, the Interrupt Mode bit is set, and the
toggle bit of the Interrupt IN endpoint changes after each data packet is sent to the host, without regard to the Status
stage.
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