net2890 ETC-unknow, net2890 Datasheet - Page 26

• Manufacturer Part Number: net2890
• Description: Interface Controller
• Manufacturer: ETC-unknow

Specification
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:
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
0
0
0
0
0
1
1
1
1
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.
Stage
IN Token
Data (1/0)
Status
FIFO
Valid
Bit
0
0
0
1
X
0
X
1
1
End of
Transfer
Response Bit
0
1
1
X
X
X
X
X
X
335 Pioneer Way, Mountain View, California 94041
TEL [phone] FAX [phone]
Packet Contents
IN PID, address, endpoint, and CRC5
DATA PID, N data bytes, and CRC16,
or NAK or STALL
ACK
Size of
Previous
Packet
X
Maximum
< Maximum
X
X
X
X
X
X
NetChip Technology, Inc., 1999
Rev 2.0, Draft 9, July 16, 1999
http://www.netchip.com
Amount of Data in
FIFO
empty
empty
empty
empty
>0
< Max Packet Length
>= Max Packet Length
empty
>0
NET2890 USB Interface Controller
bytes
N+3
Action
NAK to host
Zero length packet to host
NAK to host
Zero length packet to host
Return data to host
NAK to host
Return data to host
Zero length packet to host
Return data to host
# of
3
1
NET2890
Source
Host
Host
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