MITSUBISHI <DIGITAL ASSP>
M66290AGP/FP
USB DEVICE CONTROLLER
USB DATA TRANSFER DESCRIPTIONS
M66290A is a USB dev ice controller correspond to all
the f our ty pes of transf er (control, bulk, isochronous,
and interrupt transf er), which is compatible to USB
specif ication 1.1.
M66290A acts USB f unctions as below automatically .
(1) Bit stuf f ing/destuf f ing
(2) CRC generate/check
(3) NRZI encode/decode
(4) Packet handling
(5) USB address check
(6) Bus error handling
Theref ore, when CPU transact the operations as
f ollows, USB transf er is realized.
(1) Response to the control transf er request
(2) Permission of store and transmission of the
transmit data into the endpoint buf f er.
(Or read of the receiv ed data f rom the endpoint
buf f er)
(3) Stall handling
(4) Suspend/resume handling
Below are the descriptions about the data transf er.
Data receiv e
In data receiv e, there are dif f erences of its f unction
between setup transaction and out transaction.
In setup transaction, when receiv ed dev ice request
f rom host, 8By te request is alway s stored into f our
resistors.
When request data is receiv ed correctly ,sends back
ACK packet to host and at the same time, occurs
interrupt to CPU and urge CPU to read request.
In out transaction, af ter M66290A receiv ed OUT
token packet, host transmits data packet.
If packet of m aximum packet size or short packet
is stored into the endpoint FIFO of M66290A, and
moreov er, error is not occurred in that transf er,
M66290A transmits ACK packet to host and inf orms
CPU that the data was receiv ed by occurring buf f er
ready interrupt.
If U SB protocol error is occurred in the host data
which receiv ed v ia USB bus, or if the endpoint FIFO
is f ull, M66290A does not transmit ACK packet to
host. Host knows that the error occurred because the
ACK packet does not come, and take a step such as
data resend.
4
Data transmit
When the data of endpoint FIFO, which corresponds to
transmit request by IN token packet, is ready , M66290A
transmit the corresponded data packet to USB bus.
If the ACK packet come f rom the host f or the transmitted
data packet, a transaction completed and the endpoint
FIFO becomes empty and urge CPU to write the next
transmit data by buf f er ready interrupt.
If the transmit data, which correspond to transmit request
by IN token packet, is not exist in the endpoint FIFO,
M66290A transmit NAK packet to host when receiv ed
IN token packet f rom host and occurs interrupt and
request CPU to write transmit data.
When M66290A receiv ed IN token packet again f rom host,
M66290A transmits the data which is written.
If error is not occurred in that transf er, host transmit ACK
packet and if M66290A receiv ed it normally , a transaction
completed.
If U SB protocol error is occurred in the data which is
transmitted v ia USB bus, host does not transmit ACK
packet, so M66290A watch and wait until receiv e IN token
packet, with keeping the data to be transmitted.
RENESAS [ RENESAS TECHNOLOGY CORP ]
