net2890 ETC-unknow, net2890 Datasheet - Page 21

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

Specification
4.5.2.1 Control Read Transfer
A successful control read transfer from Control Endpoint 0 consists of the following:
Setup
Data (zero, one, or
more packets)
Status
The Setup transaction is processed in the same way as for control write transfers.
During the Data transaction, zero, one or more data packets are read from the Endpoint 0 FIFO. For each
packet:
For a successful Status transaction, the Host sends a zero length data packet, and the NET2890 responds
with an ACK. A NAK or STALL can be returned if an error occurred.
4.5.2.2 Control Read Transfer Details
For control read transfers, the host first sends eight bytes of setup information. The setup bytes are stored
into an 8-byte register bank that can be accessed from the local CPU. After the eight bytes have been stored
into the Setup Registers, the Setup Packet Interrupt status bit is set. If this interrupt is enabled, the local
interrupt IRQ# pin is asserted. The NET2890 will not respond to the host if the Setup Packet Interrupt
status bit is still set from a previous setup packet, and a new setup packet arrives from the host. This
prevents the eight bytes of the previous setup packet from being over-written before the local CPU has read
them.
The local CPU then reads the 8-byte setup packet and prepares to respond to the optional Data transactions.
The number of bytes to be transferred in the Data transactions is specified in the setup packet. When the
setup packet is received, the Control Status Phase Handshake bit is automatically set. While this bit is
set, the control status phase will be acknowledged with a NAK, allowing the local CPU to prepare its
handshake response (ACK or STALL). Once the Control Status Phase Handshake bit is cleared, the
ACK or STALL handshake will be returned to the host.
____________________________________________________________________________________
Transaction
Interrupt status bits are set and can interrupt the local CPU
The local CPU writes data to the FIFO
If there is no data in the FIFO, a NAK or zero length packet is returned to the host
The Host returns an ACK to the NET2890 if no error has occurred.
Setup Token
Data
Status
IN Token
Data (1/0)
Status
OUT Token
Data
Status
335 Pioneer Way, Mountain View, California 94041
TEL [phone] FAX [phone]
Stage
NetChip Technology, Inc., 1999
Rev 2.0, Draft 9, July 16, 1999
http://www.netchip.com
SETUP PID, address, endpoint, and CRC5
DATA0 PID, 8 data bytes, and CRC16
ACK
IN PID, address, endpoint, and CRC5
DATA PID, N data bytes, and CRC16
ACK
OUT PID, address, endpoint, and CRC5
DATA1 PID, zero length packet, and CRC5
ACK
Packet Contents
NET2890 USB Interface Controller
bytes
N+3
# of
11
3
1
3
1
3
3
1
NET2890
NET2890
NET2890
Source
Host
Host
Host
Host
Host
Host
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