AT32UC3C1512C Automotive Atmel Corporation, AT32UC3C1512C Automotive Datasheet - Page 884

• Manufacturer Part Number: AT32UC3C1512C Automotive
• Manufacturer: Atmel Corporation

9166C–AVR-08/11
• Control read
USB Bus
RXSTPI
RXOUTI
TXINI
USB Bus
RXSTPI
RXOUTI
TXINI
Wr Enable
HOST
Wr Enable
CPU
Figure 32-9. Control Write
Figure 32-10 on page 884
simultaneous write requests from the CPU and USB host.
Figure 32-10. Control Read
A NAK handshake is always generated as the first status stage command. The UESTAn.NAKINI
bit is set. It allows the user to know that the host aborts the IN data stage. As a consequence,
the user should stop processing the IN data stage and should prepare to receive the OUT status
stage by checking the UESTAn.RXOUTI bit.
The OUT retry is always ACKed. This OUT reception sets RXOUTI. Handle this with the follow-
ing software algorithm:
Once the OUT status stage has been received, the USBC waits for a SETUP request. The
SETUP request has priority over all other requests and will be ACKed.
// process the IN data stage
set TXINI
wait for RXOUTI (rising) OR TXINI (falling)
if RXOUTI is high, then process the OUT status stage
if TXINI is low, then return to process the IN data stage
SETUP
SETUP
SETUP
SETUP
HW
HW
SW
SW
SW
IN
OUT
shows a control read transaction. The USBC has to manage the
HW
HW
DATA
SW
DATA
SW
OUT
IN
HW
SW
OUT
NAK
NAK
IN
STATUS
STATUS
SW
AT32UC3C
OUT
HW
IN
SW
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